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Spectroscopic insights into high defect tolerance of Zn:CuInSe2 quantum-dot-sensitized solar cells

Abstract

Colloidal semiconductor quantum dots (QDs) are promising materials for realizing high-performance liquid-junction photovoltaic cells. Solar cells based on Zn:CuInSe2 QDs show high efficiency despite a large abundance of native defects typical of ternary I–III–VI2 semiconductors. To elucidate the reasons underlying the remarkable defect tolerance of these devices, we conduct side-by-side photovoltaic and spectroscopic studies of as-prepared and surface-modified Zn:CuInSe2 QDs. Using surface ligands with different lengths and binding affinities to the TiO2 surface, we tune the rates of both defect-related relaxation and QD-to-TiO2 electrode electron transfer. Despite their profound influence on photoluminescence dynamics, surface modifications have surprisingly little effect on photovoltaic performance suggesting that intragap defects do not impede but actually assist the photoconversion process in Zn:CuInSe2 QDs. These intragap states, identified as shallow surface-located electron traps and native Cu1+ hole-trapping defects, mediate QD interactions with the TiO2 electrode and the electrolyte, respectively, and help achieve consistent photovoltaic performance with ~85% photon-to-electron conversion efficiencies and highly reproducible power conversion efficiencies of 9–10%.

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Fig. 1: Surface structures of ZCISe QDs with different passivating ligands and their optical spectra.
Fig. 2: PL dynamics of free-standing and TiO2-coupled ZCISe QDs with different surface ligands.
Fig. 3: Internal and external quantum efficiencies of thin-anode ZCISe QD-sensitized solar cells and an underlying photoconversion mechanism.
Fig. 4: Performance characteristics and stability tests of ZCISe QD-sensitized solar cells.

Data availability

The datasets generated and/or analysed during the current study are available within the paper, its Supplementary Information and its Source Data files.

References

  1. 1.

    Nozik, A. J. et al. Semiconductor quantum dots and quantum dot arrays and applications of multiple exciton generation to third-generation photovoltaic solar cells. Chem. Rev. 110, 6873–6890 (2010).

    Article  Google Scholar 

  2. 2.

    McDonald, S. A. et al. Solution-processed PbS quantum dot infrared photodetectors and photovoltaics. Nat. Mater. 4, 138–142 (2005).

    Article  Google Scholar 

  3. 3.

    Kamat, P. V. Quantum dot solar cells. Semiconductor nanocrystals as light harvesters. J. Phys. Chem. C 112, 18737–18753 (2008).

    Article  Google Scholar 

  4. 4.

    Bernechea, M. et al. Solution-processed solar cells based on environmentally friendly AgBiS2 nanocrystals. Nat. Photon. 10, 521–525 (2016).

    Article  Google Scholar 

  5. 5.

    Semonin, O. E. et al. Peak external photocurrent quantum efficiency exceeding 100% via MEG in a quantum dot solar cell. Science 334, 1530–1533 (2011).

    Article  Google Scholar 

  6. 6.

    Schaller, R. D. & Klimov, V. I. High efficiency carrier multiplication in PbSe nanocrystals: implications for solar energy conversion. Phys. Rev. Lett. 92, 186601 (2004).

    Article  Google Scholar 

  7. 7.

    Trinh, M. T. et al. In spite of recent doubts carrier multiplication does occur in PbSe nanocrystals. Nano Lett. 8, 1713–1718 (2008).

    Article  Google Scholar 

  8. 8.

    Böhm, M. L. et al. Lead telluride quantum dot solar cells displaying external quantum efficiencies exceeding 120%. Nano Lett. 15, 7987–7993 (2015).

    Article  Google Scholar 

  9. 9.

    Ross, R. T. & Nozik, A. J. Efficiency of hot-carrier solar energy converters. J. Appl. Phys. 53, 3813–3818 (1982).

    Article  Google Scholar 

  10. 10.

    Tisdale, W. A. et al. Hot-electron transfer from semiconductor nanocrystals. Science 328, 1543–1547 (2010).

    Article  Google Scholar 

  11. 11.

    Hao, M. et al. Ligand-assisted cation-exchange engineering for high-efficiency colloidal Cs1−xFAxPbI3 quantum dot solar cells with reduced phase segregation. Nat. Energy 5, 79–88 (2020).

    Article  Google Scholar 

  12. 12.

    Sanehira, E. M. et al. Enhanced mobility CsPbI3 quantum dot arrays for record-efficiency, high-voltage photovoltaic cells. Sci. Adv. 3, eaao4204 (2017).

    Article  Google Scholar 

  13. 13.

    Zaban, A., Mićić, O. I., Gregg, B. A. & Nozik, A. J. Photosensitization of nanoporous TiO2 electrodes with InP quantum dots. Langmuir 14, 3153–3156 (1998).

    Article  Google Scholar 

  14. 14.

    Robel, I., Subramanian, V., Kuno, M. & Kamat, P. V. Quantum dot solar cells. Harvesting light energy with CdSe nanocrystals molecularly linked to mesoscopic TiO2 films. J. Am. Chem. Soc. 128, 2385–2393 (2006).

    Article  Google Scholar 

  15. 15.

    McDaniel, H., Fuke, N., Makarov, N. S., Pietryga, J. M. & Klimov, V. I. An integrated approach to realizing high-performance liquid-junction quantum dot sensitized solar cells. Nat. Commun. 4, 2887 (2013).

    Article  Google Scholar 

  16. 16.

    Du, J. et al. Zn–Cu–In–Se quantum dot solar cells with a certified power conversion efficiency of 11.6%. J. Am. Chem. Soc. 138, 4201–4209 (2016).

    Article  Google Scholar 

  17. 17.

    O’Regan, B. & Grätzel, M. A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films. Nature 353, 737–740 (1991).

    Article  Google Scholar 

  18. 18.

    Yella, A. et al. Porphyrin-sensitized solar cells with cobalt (II/III)–based redox electrolyte exceed 12 percent efficiency. Science 334, 629 (2011).

    Article  Google Scholar 

  19. 19.

    Sambur, J. B., Riha, S. C., Choi, D. & Parkinson, B. A. Influence of surface chemistry on the binding and electronic coupling of CdSe quantum dots to single crystal TiO2 surfaces. Langmuir 26, 4839–4847 (2010).

    Article  Google Scholar 

  20. 20.

    Guijarro, N., Lana-Villarreal, T., Mora-Seró, I., Bisquert, J. & Gómez, R. CdSe quantum dot-sensitized TiO2 electrodes: effect of quantum dot coverage and mode of attachment. J. Phys. Chem. C 113, 4208–4214 (2009).

    Article  Google Scholar 

  21. 21.

    Graetzel, M., Janssen, R. A. J., Mitzi, D. B. & Sargent, E. H. Materials interface engineering for solution-processed photovoltaics. Nature 488, 304–312 (2012).

    Article  Google Scholar 

  22. 22.

    Liu, Y. et al. Dependence of carrier mobility on nanocrystal size and ligand length in pbse nanocrystal solids. Nano Lett. 10, 1960–1969 (2010).

    Article  Google Scholar 

  23. 23.

    Fafarman, A. T. et al. Thiocyanate-capped nanocrystal colloids: vibrational reporter of surface chemistry and solution-based route to enhanced coupling in nanocrystal solids. J. Am. Chem. Soc. 133, 15753–15761 (2011).

    Article  Google Scholar 

  24. 24.

    Wang, W. et al. Facile secondary deposition for improving quantum dot loading in fabricating quantum dot solar cells. J. Am. Chem. Soc. 141, 4300–4307 (2019).

    Article  Google Scholar 

  25. 25.

    Xu, J. et al. 2D matrix engineering for homogeneous quantum dot coupling in photovoltaic solids. Nat. Nanotechnol. 13, 456–462 (2018).

    Article  Google Scholar 

  26. 26.

    Swarnkar, A. et al. Quantum dot–induced phase stabilization of α-CsPbI3 perovskite for high-efficiency photovoltaics. Science 354, 92–95 (2016).

    Article  Google Scholar 

  27. 27.

    Ren, Z., Yu, J., Pan, Z., Wang, J. & Zhong, X. Inorganic ligand thiosulfate-capped quantum dots for efficient quantum dot sensitized solar cells. ACS Appl. Mater. Interfaces 9, 18936–18944 (2017).

    Article  Google Scholar 

  28. 28.

    Panthani, M. G. et al. CuInSe2 quantum dot solar cells with high open-circuit voltage. J. Phys. Chem. Lett. 4, 2030–2034 (2013).

    Article  Google Scholar 

  29. 29.

    Boles, M. A., Engel, M. & Talapin, D. V. Self-assembly of colloidal nanocrystals: from intricate structures to functional materials. Chem. Rev. 116, 11220–11289 (2016).

    Article  Google Scholar 

  30. 30.

    Boles, M. A., Ling, D., Hyeon, T. & Talapin, D. V. The surface science of nanocrystals. Nat. Mater. 15, 141–153 (2016).

    Article  Google Scholar 

  31. 31.

    Anderson, N. C., Hendricks, M. P., Choi, J. J. & Owen, J. S. Ligand exchange and the stoichiometry of metal chalcogenide nanocrystals: spectroscopic observation of facile metal-carboxylate displacement and binding. J. Am. Chem. Soc. 135, 18536–18548 (2013).

    Article  Google Scholar 

  32. 32.

    Luther, J. M. et al. Structural, optical, and electrical properties of self-assembled films of PbSe nanocrystals treated with 1,2-ethanedithiol. ACS Nano 2, 271–280 (2008).

    Article  Google Scholar 

  33. 33.

    Wang, R. et al. Colloidal quantum dot ligand engineering for high performance solar cells. Energy Environ. Sci. 9, 1130–1143 (2016).

    Article  Google Scholar 

  34. 34.

    Wang, H., McNellis, E. R., Kinge, S., Bonn, M. & Cánovas, E. Tuning electron transfer rates through molecular bridges in quantum dot sensitized oxides. Nano Lett. 13, 5311–5315 (2013).

    Article  Google Scholar 

  35. 35.

    Mora-Seró, I. et al. Factors determining the photovoltaic performance of a CdSe quantum dot sensitized solar cell: the role of the linker molecule and of the counter electrode. Nanotechnology 19, 424007 (2008).

    Article  Google Scholar 

  36. 36.

    Rice, W. D., McDaniel, H., Klimov, V. I. & Crooker, S. A. Magneto-optical properties of CuInS2 nanocrystals. J. Phys. Chem. Lett. 5, 4105–4109 (2014).

    Article  Google Scholar 

  37. 37.

    Fuhr, A. S. et al. Light emission mechanisms in CuInS2 quantum dots evaluated by spectral electrochemistry. ACS Photon. 4, 2425–2435 (2017).

    Article  Google Scholar 

  38. 38.

    Jara, D. H., Stamplecoskie, K. G. & Kamat, P. V. Two distinct transitions in CuxIns2 quantum dots. Bandgap versus sub-bandgap excitations in copper-deficient structures. J. Phys. Chem. Lett. 7, 1452–1459 (2016).

    Article  Google Scholar 

  39. 39.

    Berends, A. C., Mangnus, M. J. J., Xia, C., Rabouw, F. T. & de Mello Donega, C. Optoelectronic properties of ternary I–III–VI2 semiconductor nanocrystals: bright prospects with elusive origins. J. Phys. Chem. Lett. 10, 1600–1616 (2019).

    Article  Google Scholar 

  40. 40.

    Fuhr, A., Yun, H. J., Crooker, S. A. & Klimov, V. I. Spectroscopic and magneto-optical signatures of Cu1+ and Cu2+ defects in copper indium sulfide quantum dots. ACS Nano 14, 2212–2223 (2020).

    Article  Google Scholar 

  41. 41.

    Pinchetti, V. et al. Spectro-electrochemical probing of intrinsic and extrinsic processes in exciton recombination in I–III–VI2 nanocrystals. Nano Lett. 17, 4508–4517 (2017).

    Article  Google Scholar 

  42. 42.

    Makarov, N. S., McDaniel, H., Fuke, N., Robel, I. & Klimov, V. I. Photocharging artifacts in measurements of electron transfer in quantum-dot-sensitized mesoporous titania films. J. Phys. Chem. Lett. 5, 111–118 (2014).

    Article  Google Scholar 

  43. 43.

    Li, L. et al. Efficient synthesis of highly luminescent copper indium sulfide-based core/shell nanocrystals with surprisingly long-lived emission. J. Am. Chem. Soc. 133, 1176–1179 (2011).

    Article  Google Scholar 

  44. 44.

    Zang, H. et al. Thick-shell CuInS2/ZnS quantum dots with suppressed ‘blinking’ and narrow single-particle emission line widths. Nano Lett. 17, 1787–1795 (2017).

    Article  Google Scholar 

  45. 45.

    Jeong, S. et al. Effect of the thiol−thiolate equilibrium on the photophysical properties of aqueous CdSe/ZnS nanocrystal quantum dots. J. Am. Chem. Soc. 127, 10126–10127 (2005).

    Article  Google Scholar 

  46. 46.

    Yun, H. J. et al. Charge transport mechanisms in CuInSexS2−x quantum dot films. ACS Nano 12, 12587–12596 (2018).

    Article  Google Scholar 

  47. 47.

    Hodes, G., Manassen, J. & Cahen, D. Electrocatalyic electrodes for the polysulfide redox system. J. Electrochem. Soc. 127, 544–549 (1990).

    Article  Google Scholar 

  48. 48.

    Ito, S. et al. Fabrication of thin film dye sensitized solar cells with solar to electric power conversion efficiency over 10%. Thin Solid Films 516, 4613–4619 (2008).

    Article  Google Scholar 

  49. 49.

    Du, J., Meng, X., Zhao, K., Li, Y. & Zhong, X. Performance enhancement of quantum dot sensitized solar cells by adding electrolyte additives. J. Mater. Chem. A 3, 17091–17097 (2015).

    Article  Google Scholar 

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Acknowledgements

We thank J. Yu for supplying mesoporous-carbon cathodes and Y. Wang for assistance with the EQE measurements. The studies of QD photophysical properties, QD surface functionalization and charge transfer at the QD/TiO2 interface were supported by the Solar Photochemistry Program of the Chemical Sciences, Biosciences and Geosciences Division, Office of Basic Energy Sciences, Office of Science, US Department of Energy. The research into QD synthesis and device fabrication was supported by the Laboratory Directed Research and Development programme of Los Alamos National Laboratory (LANL) under project number 20190232ER. A.S.F. was supported by the LANL African American Partnership Program.

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V.I.K. initiated the study. J.D. synthesized the QDs, developed and applied the ligand-exchange procedures and fabricated and characterized the QDSSCs. R.S. conducted the transient absorption and transient PL measurements and together with V.I.K. analysed the results. I.F. elucidated the chemical nature of QD coupling to a mesoporous-TiO2 electrode. A.S.F. conducted the cyclic voltammetry studies of the QDs. V.I.K. wrote the manuscript with contributions from all the co-authors.

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Correspondence to Victor I. Klimov.

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Supplementary Figs. 1–8, Tables 1–5, Notes 1–2 and refs. 1–8.

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Du, J., Singh, R., Fedin, I. et al. Spectroscopic insights into high defect tolerance of Zn:CuInSe2 quantum-dot-sensitized solar cells. Nat Energy 5, 409–417 (2020). https://doi.org/10.1038/s41560-020-0617-6

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