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Physical insights into non-fullerene organic photovoltaics

Nature Reviews Physics (2024)Cite this article

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Abstract

Boosted by the fast development of non-fullerene acceptors, organic photovoltaics (OPVs) have achieved breakthrough power conversion efficiencies — in excess of 20% and approaching those of state-of-the-art crystalline silicon photovoltaics. New physical properties, unusual phenomena and critical mechanisms have been uncovered in non-fullerene acceptors and related devices, all contributing to deliver advances in OPV technologies. In this Review, we summarize the photophysics and device physics of non-fullerene-acceptor-based OPVs, with emphasis on the comparison between fullerene and non-fullerene acceptors of the physical processes that affect device performance. We discuss the processes of exciton generation, diffusion, transport and separation and charge recombination in OPVs and present recent interpretations of the physics of non-fullerene-acceptor-based OPVs, looking at how driving energy affects exciton separation and how charge recombination affects voltage loss. Compiling these mechanisms — especially those that can overcome the intrinsic limitations imposed by the energy-gap law — we provide a strategy for minimizing voltage loss and discuss future research directions and challenges in the fundamentals and performance of OPVs, including new modes of operation for non-fullerene-acceptor-based OPVs.

Key points

  • Non-fullerene acceptor materials show strong visible and near-infrared absorption and thus can generate abundant excitons and photocurrent in organic photovoltaics.

  • Exciton diffusion coefficients for non-fullerene acceptors are much larger than those for fullerene acceptors. The spectral overlap between donor and non-fullerene acceptor enables long-range energy transfer from donor to acceptor.

  • Exciton separation in non-fullerene-acceptor-based devices mainly follows hole-transfer pathways and is typically much slower than in fullerene-based devices owing to morphological factors. Spontaneous photogeneration of charges and intra-moiety excimer states are also observed in non-fullerene acceptors.

  • Non-fullerene acceptors show lower energetic disorder, suppressed sub-bandgap states and reduced trap-assisted recombination and voltage loss, compared with fullerene acceptors.

  • When energy offsets are small, the weakly emissive charge-transfer states can hybridize with highly emissive local excited states of non-fullerene acceptors, leading to increased radiative efficiency for charge-transfer states and thus reduced non-radiative voltage loss.

  • The non-radiative voltage loss of non-fullerene-acceptor-based devices is largely governed by the radiative efficiency of local excited states, which is limited by the energy-gap law for organic molecules.

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Fig. 1: Molecular structures of donors and acceptors.
Fig. 2: Exciton generation and diffusion properties of non-fullerene acceptors.
Fig. 3: Exciton separation in non-fullerene-acceptor-based devices.
Fig. 4: Three-state vibronic model, non-radiative voltage loss and photoluminescence quantum yields of acceptors.
Fig. 5: The features of non-fullerene acceptors.

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References

  1. Li, G., Zhu, R. & Yang, Y. Polymer solar cells. Nat. Photon. 6, 153–161 (2012).

    Article  ADS  Google Scholar 

  2. Krebs, F. C., Espinosa, N., Hösel, M., Søndergaard, R. R. & Jørgensen, M. 25th anniversary article: rise to power — OPV-based solar parks. Adv. Mater. 26, 29–39 (2014).

    Article  Google Scholar 

  3. Inganäs, O. Organic photovoltaics over three decades. Adv. Mater. 30, 1800388 (2018).

    Article  Google Scholar 

  4. Tang, C. W. Two layer organic photovoltaic cell. Appl. Phys. Lett. 48, 183–185 (1986).

    Article  ADS  Google Scholar 

  5. Scholes, G. D. & Rumbles, G. Excitons in nanoscale systems. Nat. Mater. 5, 683–696 (2006).

    Article  ADS  Google Scholar 

  6. Brédas, J.-L., Norton, J. E., Cornil, J. & Coropceanu, V. Molecular understanding of organic solar cells: the challenges. Acc. Chem. Res. 42, 1691–1699 (2009).

    Article  Google Scholar 

  7. Mikhnenko, O. V., Blom, P. W. M. & Nguyen, T.-Q. Exciton diffusion in organic semiconductors. Energy Environ. Sci. 8, 1867–1888 (2015).

    Article  Google Scholar 

  8. Yu, G., Gao, J., Hummelen, J. C., Wudl, F. & Heeger, A. J. Polymer photovoltaic cells — enhanced efficiencies via a network of internal donor–acceptor heterojunctions. Science 270, 1789–1791 (1995).

    Article  ADS  Google Scholar 

  9. Halls, J. J. M. et al. Efficient photodiodes from interpenetrating polymer networks. Nature 376, 498–500 (1995).

    Article  ADS  Google Scholar 

  10. Zhu, L., Yi, Y. & Wei, Z. Exciton binding energies of nonfullerene small molecule acceptors: implication for exciton dissociation driving forces in organic solar cells. J. Phys. Chem. C 122, 22309–22316 (2018).

    Article  Google Scholar 

  11. Scharber, M. C. On the efficiency limit of conjugated polymer:fullerene-based bulk heterojunction solar cells. Adv. Mater. 28, 1994–2001 (2016).

    Article  Google Scholar 

  12. Cheng, P., Li, G., Zhan, X. & Yang, Y. Next-generation organic photovoltaics based on non-fullerene acceptors. Nat. Photon. 12, 131–142 (2018).

    Article  ADS  Google Scholar 

  13. Zhan, X. et al. A high-mobility electron-transport polymer with broad absorption and its use in field-effect transistors and all-polymer solar cells. J. Am. Chem. Soc. 129, 7246–7247 (2007).

    Article  Google Scholar 

  14. Zhan, X. et al. Rylene and related diimides for organic electronics. Adv. Mater. 23, 268–284 (2011).

    Article  ADS  Google Scholar 

  15. Yan, C. et al. Non-fullerene acceptors for organic solar cells. Nat. Rev. Mater. 3, 18003 (2018).

    Article  ADS  Google Scholar 

  16. Hou, J., Inganäs, O., Friend, R. H. & Gao, F. Organic solar cells based on non-fullerene acceptors. Nat. Mater. 17, 119–128 (2018).

    Article  ADS  Google Scholar 

  17. Zhang, J., Tan, H. S., Guo, X., Facchetti, A. & Yan, H. Material insights and challenges for non-fullerene organic solar cells based on small molecular acceptors. Nat. Energy 3, 720–731 (2018).

    Article  ADS  Google Scholar 

  18. Bai, H. et al. An electron acceptor based on indacenodithiophene and 1,1-dicyanomethylene-3-indanone for fullerene-free organic solar cells. J. Mater. Chem. A 3, 1910–1914 (2015).

    Article  Google Scholar 

  19. Lin, Y. et al. High-performance fullerene-free polymer solar cells with 6.31% efficiency. Energy Environ. Sci. 8, 610–616 (2015).

    Article  Google Scholar 

  20. Lin, Y. et al. An electron acceptor challenging fullerenes for efficient polymer solar cells. Adv. Mater. 27, 1170–1174 (2015).

    Article  Google Scholar 

  21. Wang, J. & Zhan, X. Fused-ring electron acceptors for photovoltaics and beyond. Acc. Chem. Res. 54, 132–143 (2021).

    Article  Google Scholar 

  22. Wang, J., Xue, P., Jiang, Y., Huo, Y. & Zhan, X. The principles, design and applications of fused-ring electron acceptors. Nat. Rev. Chem. 6, 614–634 (2022).

    Article  Google Scholar 

  23. Markina, A. et al. Chemical design rules for non-fullerene acceptors in organic solar cells. Adv. Energy Mater. 11, 2102363 (2021).

    Article  Google Scholar 

  24. Fu, Y. et al. Molecular orientation-dependent energetic shifts in solution-processed non-fullerene acceptors and their impact on organic photovoltaic performance. Nat. Commun. 14, 1870 (2023).

    Article  Google Scholar 

  25. Swick, S. M. et al. Closely packed, low reorganization energy π-extended postfullerene acceptors for efficient polymer solar cells. Proc. Natl Acad. Sci. USA 115, E8341–E8348 (2018).

    Article  Google Scholar 

  26. Kashani, S., Wang, Z., Risko, C. & Ade, H. Relating reorganization energies, exciton diffusion length and non-radiative recombination to the room temperature UV–Vis absorption spectra of NF-SMA. Mater. Horiz. 10, 443–453 (2023).

    Article  Google Scholar 

  27. Zheng, Z. et al. Tandem organic solar cell with 20.2% efficiency. Joule 6, 171–184 (2022).

    Article  ADS  Google Scholar 

  28. Dai, S. et al. Enhancing the performance of polymer solar cells via core engineering of NIR-absorbing electron acceptors. Adv. Mater. 30, 1706571 (2018).

    Article  Google Scholar 

  29. Wang, J. et al. Effect of isomerization on high-performance nonfullerene electron acceptors. J. Am. Chem. Soc. 140, 9140–9147 (2018).

    Article  Google Scholar 

  30. Liang, Y. et al. Organic solar cells using oligomer acceptors for improved stability and efficiency. Nat. Energy 7, 1180–1190 (2022).

    Article  ADS  Google Scholar 

  31. Wang, W. et al. Fused hexacyclic nonfullerene acceptor with strong near-infrared absorption for semitransparent organic solar cells with 9.77% efficiency. Adv. Mater. 29, 1701308 (2017).

    Article  Google Scholar 

  32. Zhu, J. et al. Naphthodithiophene-based nonfullerene acceptor for high-performance organic photovoltaics: effect of extended conjugation. Adv. Mater. 30, 1704713 (2018).

    Article  Google Scholar 

  33. Li, T. et al. Fused tris(thienothiophene)-based electron acceptor with strong near-infrared absorption for high-performance as-cast solar cells. Adv. Mater. 30, 1705969 (2018).

    Article  ADS  Google Scholar 

  34. Yuan, J. et al. Single-junction organic solar cell with over 15% efficiency using fused-ring acceptor with electron-deficient core. Joule 3, 1140–1151 (2019).

    Article  Google Scholar 

  35. Jia, Z. et al. Near-infrared absorbing acceptor with suppressed triplet exciton generation enabling high performance tandem organic solar cells. Nat. Commun. 14, 1236 (2023).

    Article  ADS  Google Scholar 

  36. Jia, B. et al. Enhancing the performance of a fused-ring electron acceptor by unidirectional extension. J. Am. Chem. Soc. 141, 19023–19031 (2019).

    Article  Google Scholar 

  37. Luo, Z. et al. Fine-tuning energy levels via asymmetric end groups enables polymer solar cells with efficiencies over 17%. Joule 4, 1236–1247 (2020).

    Article  Google Scholar 

  38. Gao, Y. et al. High-performance small molecule organic solar cells enabled by a symmetric–asymmetric alloy acceptor with a broad composition tolerance. Adv. Mater. 35, 2300531 (2023).

    Article  Google Scholar 

  39. Dai, S. et al. Fused nonacyclic electron acceptors for efficient polymer solar cells. J. Am. Chem. Soc. 139, 1336–1343 (2017).

    Article  Google Scholar 

  40. Xie, D. et al. A novel thiophene-fused ending group enabling an excellent small molecule acceptor for high-performance fullerene-free polymer solar cells with 11.8% efficiency. Sol. RRL 1, 1700044 (2017).

    Article  Google Scholar 

  41. Yao, H. et al. Achieving highly efficient nonfullerene organic solar cells with improved intermolecular interaction and open-circuit voltage. Adv. Mater. 29, 1700254 (2017).

    Article  Google Scholar 

  42. Cui, Y. et al. Single-junction organic photovoltaic cells with approaching 18% efficiency. Adv. Mater. 32, 1908205 (2020).

    Article  Google Scholar 

  43. Yao, H. et al. Design, synthesis, and photovoltaic characterization of a small molecular acceptor with an ultra-narrow band gap. Angew. Chem. Int. Ed. 56, 3045–3049 (2017).

    Article  Google Scholar 

  44. Liu, W. et al. Theory-guided material design enabling high-performance multifunctional semitransparent organic photovoltaics without optical modulations. Adv. Mater. 34, 2200337 (2022).

    Article  Google Scholar 

  45. Lin, Y. et al. A facile planar fused-ring electron acceptor for as-cast polymer solar cells with 8.71% efficiency. J. Am. Chem. Soc. 138, 2973–2976 (2016).

    Article  Google Scholar 

  46. Lin, Y. et al. High-performance electron acceptor with thienyl side chains for organic photovoltaics. J. Am. Chem. Soc. 138, 4955–4961 (2016).

    Article  Google Scholar 

  47. Wang, J. et al. Enhancing performance of nonfullerene acceptors via side-chain conjugation strategy. Adv. Mater. 29, 1702125 (2017).

    Article  Google Scholar 

  48. Li, C. et al. Non-fullerene acceptors with branched side chains and improved molecular packing to exceed 18% efficiency in organic solar cells. Nat. Energy 6, 605–613 (2021).

    Article  ADS  Google Scholar 

  49. Kim, J. H., Schembri, T., Bialas, D., Stolte, M. & Würthner, F. Slip-stacked J-aggregate materials for organic solar cells and photodetectors. Adv. Mater. 34, 2104678 (2022).

    Article  Google Scholar 

  50. Kupgan, G., Chen, X.-K. & Brédas, J.-L. Molecular packing of non-fullerene acceptors for organic solar cells: distinctive local morphology in Y6 vs. ITIC derivatives. Mater. Today Adv. 11, 100154 (2021).

    Article  Google Scholar 

  51. Chen, K., Barker, A. J., Reish, M. E., Gordon, K. C. & Hodgkiss, J. M. Broadband ultrafast photoluminescence spectroscopy resolves charge photogeneration via delocalized hot excitons in polymer:fullerene photovoltaic blends. J. Am. Chem. Soc. 135, 18502–18512 (2013).

    Article  Google Scholar 

  52. Chandrabose, S. et al. High exciton diffusion coefficients in fused ring electron acceptor films. J. Am. Chem. Soc. 141, 6922–6929 (2019).

    Article  Google Scholar 

  53. Wang, R. et al. Charge separation from an intra-moiety intermediate state in the high-performance PM6:Y6 organic photovoltaic blend. J. Am. Chem. Soc. 142, 12751–12759 (2020).

    Article  Google Scholar 

  54. Firdaus, Y. et al. Long-range exciton diffusion in molecular non-fullerene acceptors. Nat. Commun. 11, 5220 (2020).

    Article  ADS  Google Scholar 

  55. Xie, Y. et al. Bright short-wavelength infrared organic light-emitting devices. Nat. Photon. 16, 752–761 (2022).

    Article  ADS  Google Scholar 

  56. Park, S. Y. et al. Photophysical pathways in efficient bilayer organic solar cells: the importance of interlayer energy transfer. Nano Energy 84, 105924 (2021).

    Article  Google Scholar 

  57. Sajjad, M. T., Ruseckas, A., Jagadamma, L. K., Zhang, Y. & Samuel, I. D. W. Long-range exciton diffusion in non-fullerene acceptors and coarse bulk heterojunctions enable highly efficient organic photovoltaics. J. Mater. Chem. A 8, 15687–15694 (2020).

    Article  Google Scholar 

  58. Zhu, L. et al. Single-junction organic solar cells with over 19% efficiency enabled by a refined double-fibril network morphology. Nat. Mater. 21, 656–663 (2022).

    Article  ADS  Google Scholar 

  59. Zhang, K.-N. et al. Exploring the mechanisms of exciton diffusion improvement in ternary polymer solar cells: from ultrafast to ultraslow temporal scale. Nano Energy 79, 105513 (2021).

    Article  Google Scholar 

  60. Lo Gerfo, M. G., Bolzonello, L., Bernal-Texca, F., Martorell, J. & van Hulst, N. F. Spatiotemporal mapping uncouples exciton diffusion from singlet–singlet annihilation in the electron acceptor Y6. J. Phys. Chem. Lett. 14, 1999–2005 (2023).

    Article  Google Scholar 

  61. Lee, T. H. et al. Organic planar heterojunction solar cells and photodetectors tailored to the exciton diffusion length scale of a non-fullerene acceptor. Adv. Funct. Mater. 32, 2208001 (2022).

    Article  Google Scholar 

  62. Sajjad, M. T., Ruseckas, A. & Samuel, I. D. W. Enhancing exciton diffusion length provides new opportunities for organic photovoltaics. Matter 3, 341–354 (2020).

    Article  Google Scholar 

  63. Karuthedath, S. et al. Intrinsic efficiency limits in low-bandgap non-fullerene acceptor organic solar cells. Nat. Mater. 20, 378–384 (2021).

    Article  ADS  Google Scholar 

  64. Bi, Z. et al. Observing long-range non-fullerene backbone ordering in real-space to improve charge transport properties of organic solar cells. J. Mater. Chem. A 9, 16733–16742 (2021).

    Article  Google Scholar 

  65. Chang, Y., Zhu, X., Lu, K. & Wei, Z. Progress and prospects of thick-film organic solar cells. J. Mater. Chem. A 9, 3125–3150 (2021).

    Article  Google Scholar 

  66. Cai, Y. et al. Vertically optimized phase separation with improved exciton diffusion enables efficient organic solar cells with thick active layers. Nat. Commun. 13, 2369 (2022).

    Article  ADS  Google Scholar 

  67. Ng, L. W. T., Lee, S. W., Chang, D. W., Hodgkiss, J. M. & Vak, D. Organic photovoltaics’ new renaissance: advances toward roll-to-roll manufacturing of non-fullerene acceptor organic photovoltaics. Adv. Mater. Technol. 7, 2101556 (2022).

    Article  Google Scholar 

  68. Zhang, J. et al. Sequentially deposited versus conventional nonfullerene organic solar cells: interfacial trap states, vertical stratification, and exciton dissociation. Adv. Energy Mater. 9, 1902145 (2019).

    Article  Google Scholar 

  69. Cui, Y. et al. Toward efficient polymer solar cells processed by a solution-processed layer-by-layer approach. Adv. Mater. 30, 1802499 (2018).

    Article  Google Scholar 

  70. Lin, Y. et al. Balanced partnership between donor and acceptor components in nonfullerene organic solar cells with >12% efficiency. Adv. Mater. 30, 1706363 (2018).

    Article  ADS  Google Scholar 

  71. Li, P. et al. Synergistic effect of dielectric property and energy transfer on charge separation in non-fullerene-based solar cells. Angew. Chem. Int. Ed. 60, 15054–15062 (2021).

    Article  Google Scholar 

  72. Barker, A. J., Chen, K. & Hodgkiss, J. M. Distance distributions of photogenerated charge pairs in organic photovoltaic cells. J. Am. Chem. Soc. 136, 12018–12026 (2014).

    Article  Google Scholar 

  73. Hwang, I. W. et al. Ultrafast electron transfer and decay dynamics in a small band gap bulk heterojunction material. Adv. Mater. 19, 2307–2312 (2007).

    Article  Google Scholar 

  74. Tong, M. et al. Charge carrier photogeneration and decay dynamics in the poly(2,7-carbazole) copolymer PCDTBT and in bulk heterojunction composites with PC70BM. Phys. Rev. B 81, 125210 (2010).

    Article  ADS  Google Scholar 

  75. Cowan, S. R., Banerji, N., Leong, W. L. & Heeger, A. J. Charge formation, recombination, and sweep-out dynamics in organic solar cells. Adv. Funct. Mater. 22, 1116–1128 (2012).

    Article  Google Scholar 

  76. Grancini, G. et al. Hot exciton dissociation in polymer solar cells. Nat. Mater. 12, 29–33 (2013).

    Article  ADS  Google Scholar 

  77. Hinrichsen, T. F. et al. Long-lived and disorder-free charge transfer states enable endothermic charge separation in efficient non-fullerene organic solar cells. Nat. Commun. 11, 5617 (2020).

    Article  ADS  Google Scholar 

  78. Perdigón-Toro, L. et al. Understanding the role of order in Y-series non-fullerene solar cells to realize high open-circuit voltages. Adv. Energy Mater. 12, 2103422 (2022).

    Article  Google Scholar 

  79. Zhong, Y. et al. Sub-picosecond charge-transfer at near-zero driving force in polymer:non-fullerene acceptor blends and bilayers. Nat. Commun. 11, 833 (2020).

    Article  ADS  Google Scholar 

  80. Zhang, G. et al. Delocalization of exciton and electron wavefunction in non-fullerene acceptor molecules enables efficient organic solar cells. Nat. Commun. 11, 3943 (2020).

    Article  ADS  Google Scholar 

  81. Scharber, M. C. et al. Design rules for donors in bulk-heterojunction solar cells — towards 10% energy-conversion efficiency. Adv. Mater. 18, 789–794 (2006).

    Article  Google Scholar 

  82. Chen, Z. et al. Ultrafast energy transfer from polymer donors facilitating spectral uniform photocurrent generation and low energy loss in high-efficiency nonfullerene organic solar cells. Energy Environ. Sci. 16, 3373–3380 (2023).

    Article  Google Scholar 

  83. Li, S. et al. Highly efficient fullerene-free organic solar cells operate at near zero highest occupied molecular orbital offsets. J. Am. Chem. Soc. 141, 3073–3082 (2019).

    Article  Google Scholar 

  84. Sun, C. et al. High efficiency polymer solar cells with efficient hole transfer at zero highest occupied molecular orbital offset between methylated polymer donor and brominated acceptor. J. Am. Chem. Soc. 142, 1465–1474 (2020).

    Article  Google Scholar 

  85. Vandewal, K., Tvingstedt, K., Gadisa, A., Inganäs, O. & Manca, J. V. Relating the open-circuit voltage to interface molecular properties of donor:acceptor bulk heterojunction solar cells. Phys. Rev. B 81, 125204 (2010).

    Article  ADS  Google Scholar 

  86. Liu, J. et al. Fast charge separation in a non-fullerene organic solar cell with a small driving force. Nat. Energy 1, 16089 (2016).

    Article  ADS  Google Scholar 

  87. Hörmann, U. et al. Quantification of energy losses in organic solar cells from temperature-dependent device characteristics. Phys. Rev. B 88, 235307 (2013).

    Article  ADS  Google Scholar 

  88. Chen, S. et al. Efficient nonfullerene organic solar cells with small driving forces for both hole and electron transfer. Adv. Mater. 30, 1804215 (2018).

    Article  Google Scholar 

  89. Classen, A. et al. The role of exciton lifetime for charge generation in organic solar cells at negligible energy-level offsets. Nat. Energy 5, 711–719 (2020).

    Article  ADS  Google Scholar 

  90. Sworakowski, J. How accurate are energies of HOMO and LUMO levels in small-molecule organic semiconductors determined from cyclic voltammetry or optical spectroscopy? Synth. Met. 235, 125–130 (2018).

    Article  Google Scholar 

  91. Bertrandie, J. et al. The energy level conundrum of organic semiconductors in solar cells. Adv. Mater. 34, 2202575 (2022).

    Article  Google Scholar 

  92. Perdigón-Toro, L. et al. Barrierless free charge generation in the high-performance PM6:Y6 bulk heterojunction non-fullerene solar cell. Adv. Mater. 32, 1906763 (2020).

    Article  Google Scholar 

  93. Schwarze, M. et al. Impact of molecular quadrupole moments on the energy levels at organic heterojunctions. Nat. Commun. 10, 2466 (2019).

    Article  ADS  Google Scholar 

  94. Eisner, F. & Nelson, J. Barrierless charge generation at non-fullerene organic heterojunctions comes at a cost. Joule 5, 1319–1322 (2021).

    Article  Google Scholar 

  95. Li, X. E. et al. Mapping the energy level alignment at donor/acceptor interfaces in non-fullerene organic solar cells. Nat. Commun. 13, 2046 (2022).

    Article  ADS  Google Scholar 

  96. Gorenflot, J. et al. Increasing the ionization energy offset to increase the quantum efficiency in non-fullerene acceptor-based organic solar cells: how far can we go? Adv. Mater. Interfaces 10, 2202515 (2023).

    Article  Google Scholar 

  97. Nakano, K. et al. Anatomy of the energetic driving force for charge generation in organic solar cells. Nat. Commun. 10, 2520 (2019).

    Article  ADS  Google Scholar 

  98. Chen, X.-K., Coropceanu, V. & Brédas, J.-L. Assessing the nature of the charge-transfer electronic states in organic solar cells. Nat. Commun. 9, 5295 (2018).

    Article  ADS  Google Scholar 

  99. Eisner, F. D. et al. Hybridization of local exciton and charge-transfer states reduces nonradiative voltage losses in organic solar cells. J. Am. Chem. Soc. 141, 6362–6374 (2019).

    Article  Google Scholar 

  100. Xie, Y. et al. Assessing the energy offset at the electron donor/acceptor interface in organic solar cells through radiative efficiency measurements. Energy Environ. Sci. 12, 3556–3566 (2019).

    Article  Google Scholar 

  101. Coropceanu, V., Chen, X.-K., Wang, T., Zheng, Z. & Brédas, J.-L. Charge-transfer electronic states in organic solar cells. Nat. Rev. Mater. 4, 689–707 (2019).

    Article  ADS  Google Scholar 

  102. Jailaubekov, A. E. et al. Hot charge-transfer excitons set the time limit for charge separation at donor/acceptor interfaces in organic photovoltaics. Nat. Mater. 12, 66–73 (2013).

    Article  ADS  Google Scholar 

  103. Kurpiers, J. et al. Probing the pathways of free charge generation in organic bulk heterojunction solar cells. Nat. Commun. 9, 2038 (2018).

    Article  ADS  Google Scholar 

  104. Vandewal, K. et al. Efficient charge generation by relaxed charge-transfer states at organic interfaces. Nat. Mater. 13, 63–68 (2014).

    Article  ADS  Google Scholar 

  105. Gélinas, S. et al. Ultrafast long-range charge separation in organic semiconductor photovoltaic diodes. Science 343, 512–516 (2014).

    Article  ADS  Google Scholar 

  106. Natsuda, S.-I. et al. Cascaded energy landscape as a key driver for slow yet efficient charge separation with small energy offset in organic solar cells. Energy Environ. Sci. 15, 1545–1555 (2022).

    Article  Google Scholar 

  107. Gregg, B. A. Entropy of charge separation in organic photovoltaic cells: the benefit of higher dimensionality. J. Phys. Chem. Lett. 2, 3013–3015 (2011).

    Article  Google Scholar 

  108. Yan, Y. et al. The role of entropy gains in the exciton separation in organic solar cells. Macromol. Rapid Commun. 43, 2100903 (2022).

    Article  Google Scholar 

  109. Bakulin, A. A. et al. The role of driving energy and delocalized states for charge separation in organic semiconductors. Science 335, 1340–1344 (2012).

    Article  ADS  Google Scholar 

  110. Price, M. B. et al. Free charge photogeneration in a single component high photovoltaic efficiency organic semiconductor. Nat. Commun. 13, 2827 (2022).

    Article  ADS  Google Scholar 

  111. Zhang, J. et al. Direct observation of increased free carrier generation owing to reduced exciton binding energies in polymerized small-molecule acceptors. J. Phys. Chem. Lett. 13, 8816–8824 (2022).

    Article  Google Scholar 

  112. Sağlamkaya, E. et al. What is special about Y6; the working mechanism of neat Y6 organic solar cells. Mater. Horiz. 10, 1825–1834 (2023).

    Article  Google Scholar 

  113. Liu, J. et al. Charge separation boosts exciton diffusion in fused ring electron acceptors. J. Mater. Chem. A 8, 23304–23312 (2020).

    Article  Google Scholar 

  114. Wang, Y. et al. Quasi-homojunction organic nonfullerene photovoltaics featuring fundamentals distinct from bulk heterojunction. Adv. Mater. 34, 2206717 (2022).

    Article  Google Scholar 

  115. Zhang, Z. et al. Single photovoltaic material solar cells with enhanced exciton dissociation and extended electron diffusion. Cell Rep. Phys. Sci. 3, 100895 (2022).

    Article  Google Scholar 

  116. Wu, J. et al. Exceptionally low charge trapping enables highly efficient organic bulk heterojunction solar cells. Energy Environ. Sci. 13, 2422–2430 (2020).

    Article  Google Scholar 

  117. Karki, A. et al. Understanding the high performance of over 15% efficiency in single-junction bulk heterojunction organic solar cells. Adv. Mater. 31, 1903868 (2019).

    Article  Google Scholar 

  118. Liu, S. et al. High-efficiency organic solar cells with low non-radiative recombination loss and low energetic disorder. Nat. Photon. 14, 300–305 (2020).

    Article  ADS  Google Scholar 

  119. Kaiser, C. et al. A universal Urbach rule for disordered organic semiconductors. Nat. Commun. 12, 3988 (2021).

    Article  ADS  Google Scholar 

  120. Zarrabi, N. et al. Charge-generating mid-gap trap states define the thermodynamic limit of organic photovoltaic devices. Nat. Commun. 11, 5567 (2020).

    Article  ADS  Google Scholar 

  121. Zeiske, S. et al. Direct observation of trap-assisted recombination in organic photovoltaic devices. Nat. Commun. 12, 3603 (2021).

    Article  ADS  Google Scholar 

  122. Li, W. et al. Organic solar cells with near-unity charge generation yield. Energy Environ. Sci. 14, 6484–6493 (2021).

    Article  Google Scholar 

  123. Menke, S. M., Ran, N. A., Bazan, G. C. & Friend, R. H. Understanding energy loss in organic solar cells: toward a new efficiency regime. Joule 2, 25–35 (2018).

    Article  Google Scholar 

  124. Li, W., Hendriks, K. H., Furlan, A., Wienk, M. M. & Janssen, R. A. J. High quantum efficiencies in polymer solar cells at energy losses below 0.6 eV. J. Am. Chem. Soc. 137, 2231–2234 (2015).

    Article  Google Scholar 

  125. Kawashima, K., Tamai, Y., Ohkita, H., Osaka, I. & Takimiya, K. High-efficiency polymer solar cells with small photon energy loss. Nat. Commun. 6, 10085 (2015).

    Article  ADS  Google Scholar 

  126. Ran, N. A. et al. Harvesting the full potential of photons with organic solar cells. Adv. Mater. 28, 1482–1488 (2016).

    Article  Google Scholar 

  127. Xie, Y. & Wu, H. Balancing charge generation and voltage loss toward efficient nonfullerene organic solar cells. Mater. Today Adv. 5, 100048 (2020).

    Article  Google Scholar 

  128. Tvingstedt, K. et al. Electroluminescence from charge transfer states in polymer solar cells. J. Am. Chem. Soc. 131, 11819–11824 (2009).

    Article  Google Scholar 

  129. Vandewal, K., Mertens, S., Benduhn, J. & Liu, Q. The cost of converting excitons into free charge carriers in organic solar cells. J. Phys. Chem. Lett. 11, 129–135 (2020).

    Article  Google Scholar 

  130. Yao, J. et al. Quantifying losses in open-circuit voltage in solution-processable solar cells. Phys. Rev. Appl. 4, 014020 (2015).

    Article  ADS  Google Scholar 

  131. Rau, U. Reciprocity relation between photovoltaic quantum efficiency and electroluminescent emission of solar cells. Phys. Rev. B 76, 085303 (2007).

    Article  ADS  Google Scholar 

  132. Chen, X.-K. et al. A unified description of non-radiative voltage losses in organic solar cells. Nat. Energy 6, 799–806 (2021).

    Article  ADS  Google Scholar 

  133. Qian, D. et al. Design rules for minimizing voltage losses in high-efficiency organic solar cells. Nat. Mater. 17, 703–709 (2018).

    Article  ADS  Google Scholar 

  134. Di Nuzzo, D. et al. Improved film morphology reduces charge carrier recombination into the triplet excited state in a small bandgap polymer-fullerene photovoltaic cell. Adv. Mater. 22, 4321–4324 (2010).

    Article  Google Scholar 

  135. Rao, A. et al. The role of spin in the kinetic control of recombination in organic photovoltaics. Nature 500, 435–439 (2013).

    Article  ADS  Google Scholar 

  136. Gillett, A. J. et al. The role of charge recombination to triplet excitons in organic solar cells. Nature 597, 666–671 (2021).

    Article  ADS  Google Scholar 

  137. Liu, X., Li, Y., Ding, K. & Forrest, S. Energy loss in organic photovoltaics: nonfullerene versus fullerene acceptors. Phys. Rev. Appl. 11, 024060 (2019).

    Article  ADS  Google Scholar 

  138. Li, W. et al. A high‐efficiency organic solar cell enabled by the strong intramolecular electron push–pull effect of the nonfullerene acceptor. Adv. Mater. 30, 1707170 (2018).

    Article  ADS  Google Scholar 

  139. Liu, X. et al. A high dielectric constant non-fullerene acceptor for efficient bulk-heterojunction organic solar cells. J. Mater. Chem. A 6, 395–403 (2018).

    Article  ADS  Google Scholar 

  140. Xu, B. et al. Donor conjugated polymers with polar side chain groups: the role of dielectric constant and energetic disorder on photovoltaic performance. Adv. Funct. Mater. 28, 1803418 (2018).

    Article  Google Scholar 

  141. Englman, R. & Jortner, J. The energy gap law for radiationless transitions in large molecules. Mol. Phys. 18, 145–164 (1970).

    Article  ADS  Google Scholar 

  142. Nitzan, A., Mukamel, S. & Jortner, J. Energy gap law for vibrational relaxation of a molecule in a dense medium. J. Chem. Phys. 63, 200–207 (1975).

    Article  ADS  Google Scholar 

  143. Zampetti, A., Minotto, A. & Cacialli, F. Near-infrared (NIR) organic light-emitting diodes (OLEDs): challenges and opportunities. Adv. Funct. Mater. 29, 1807623 (2019).

    Article  Google Scholar 

  144. Benduhn, J. et al. Intrinsic non-radiative voltage losses in fullerene-based organic solar cells. Nat. Energy 2, 17053 (2017).

    Article  ADS  Google Scholar 

  145. Collado-Fregoso, E. et al. Energy-gap law for photocurrent generation in fullerene-based organic solar cells: the case of low-donor-content blends. J. Am. Chem. Soc. 141, 2329–2341 (2019).

    Article  Google Scholar 

  146. Ullbrich, S. et al. Emissive and charge-generating donor–acceptor interfaces for organic optoelectronics with low voltage losses. Nat. Mater. 18, 459–464 (2019).

    Article  ADS  Google Scholar 

  147. Azzouzi, M. et al. Nonradiative energy losses in bulk-heterojunction organic photovoltaics. Phys. Rev. X 8, 031055 (2018).

    Google Scholar 

  148. Azzouzi, M., Kirchartz, T. & Nelson, J. Factors controlling open-circuit voltage losses in organic solar cells. Trends Chem. 1, 49–62 (2019).

    Article  Google Scholar 

  149. Wei, Y.-C. et al. Overcoming the energy gap law in near-infrared OLEDs by exciton–vibration decoupling. Nat. Photon. 14, 570–577 (2020).

    Article  ADS  Google Scholar 

  150. Wang, S.-F. et al. Polyatomic molecules with emission quantum yields >20% enable efficient organic light-emitting diodes in the NIR(II) window. Nat. Photon. 16, 843–850 (2022).

    Article  ADS  Google Scholar 

  151. Wei, Y.-C., Kuo, K.-H., Chi, Y. & Chou, P.-T. Efficient near-infrared luminescence of self-assembled platinum(II) complexes: from fundamentals to applications. Acc. Chem. Res. 56, 689–699 (2023).

    Article  Google Scholar 

  152. Liu, Q. et al. Narrow electroluminescence linewidths for reduced nonradiative recombination in organic solar cells and near-infrared light-emitting diodes. Joule 5, 2365–2379 (2021).

    Article  Google Scholar 

  153. Zuo, L. et al. Dilution effect for highly efficient multiple-component organic solar cells. Nat. Nanotechnol. 17, 53–60 (2022).

    Article  ADS  Google Scholar 

  154. Wang, Y. et al. Origins of the open-circuit voltage in ternary organic solar cells and design rules for minimized voltage losses. Nat. Energy 8, 978–988 (2023).

    Article  ADS  Google Scholar 

  155. Wang, J. et al. Tandem organic solar cells with 20.6% efficiency enabled by reduced voltage losses. Natl Sci. Rev. 10, nwad085 (2023).

    Article  Google Scholar 

  156. Kroh, D. et al. Identifying the signatures of intermolecular interactions in blends of PM6 with Y6 and N4 using absorption spectroscopy. Adv. Funct. Mater. 32, 2205711 (2022).

    Article  Google Scholar 

  157. Mondelli, P. et al. Meta-analysis: the molecular organization of non-fullerene acceptors. Mater. Horiz. 7, 1062–1072 (2020).

    Article  Google Scholar 

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Acknowledgements

X.Z. thanks the National Science Foundation of China (No. U21A20101). H.W. thanks the National Nature Science Foundation of China (No. 52273177).

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Authors and Affiliations

  1. Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, School of Materials Science and Engineering, Peking University, Beijing, China

    Jiayu Wang & Xiaowei Zhan

  2. Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, China

    Yuan Xie & Hongbin Wu

  3. MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington, New Zealand

    Kai Chen & Justin M. Hodgkiss

  4. Robinson Research Institute, Victoria University of Wellington, Wellington, New Zealand

    Kai Chen

  5. The Dodd-Walls Centre for Photonic and Quantum Technologies, University of Otago, Dunedin, New Zealand

    Kai Chen

  6. School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand

    Justin M. Hodgkiss

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  1. Jiayu Wang
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J.W., Y.X. and K.C. contributed equally to this work. All authors researched data and contributed to the writing of the article.

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Wang, J., Xie, Y., Chen, K. et al. Physical insights into non-fullerene organic photovoltaics. Nat Rev Phys (2024). https://doi.org/10.1038/s42254-024-00719-y

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