Overcoming the energy gap law in near-infrared OLEDs by exciton–vibration decoupling


The development of high-performance near-infrared organic light-emitting diodes is hindered by strong non-radiative processes as governed by the energy gap law. Here, we show that exciton delocalization, which serves to decouple the exciton band from highly vibrational ladders in the S0 ground state, can bring substantial enhancements in the photoluminescence quantum yield of emitters, bypassing the energy gap law. Experimental proof is provided by the design and synthesis of a series of new Pt(ii) complexes with a delocalization length of 5–9 molecules that emit at 866–960 nm with a photoluminescence quantum yield of 5–12% in solid films. The corresponding near-infrared organic light-emitting diodes emit light with a 930 nm peak wavelength and a high external quantum efficiency up to 2.14% and a radiance of 41.6 W sr−1 m−2. Both theoretical and experimental results confirm the exciton–vibration decoupling strategy, which should be broadly applicable to other well-aligned molecular solids.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Partitioning of reorganization energy by exciton delocalization.
Fig. 2: Molecular structures and photophysical properties.
Fig. 3: Analysis of GIXD results.
Fig. 4: Probing delocalization length from two-exciton signals through time-resolved step-scan Fourier transform UV–vis spectroscopy.
Fig. 5: Device characteristics of optimized NIR OLEDs.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.


  1. 1.

    Caspar, J. V. & Meyer, T. J. Application of the energy gap law to nonradiative, excited-state decay. J. Phys. Chem. 87, 952–957 (1983).

    Article  Google Scholar 

  2. 2.

    Treadway, J. A. et al. Effect of delocalization and rigidity in the acceptor ligand on MLCT excited-state decay. Inorg. Chem. 35, 2242–2246 (1996).

    Article  Google Scholar 

  3. 3.

    Wilson, J. S. et al. The energy gap law for triplet states in Pt-containing conjugated polymers and monomers. J. Am. Chem. Soc. 123, 9412–9417 (2001).

    Article  Google Scholar 

  4. 4.

    Whittle, C. E., Weinstein, J. A., George, M. W. & Schanze, K. S. Photophysics of diimine platinum(ii) bis-acetylide complexes. Inorg. Chem. 40, 4053–4062 (2001).

    Article  Google Scholar 

  5. 5.

    Jelle, B. P., Kalnæs, S. E. & Gao, T. Low-emissivity materials for building applications: a state-of-the-art review and future research perspectives. Energy Buildings 96, 329–356 (2015).

    Article  Google Scholar 

  6. 6.

    Xiang, H., Cheng, J., Ma, X., Zhou, X. & Chruma, J. J. Near-infrared phosphorescence: materials and applications. Chem. Soc. Rev. 42, 6128–6185 (2013).

    Article  Google Scholar 

  7. 7.

    Tessler, N., Medvedev, V., Kazes, M., Kan, S. & Banin, U. Efficient near-infrared polymer nanocrystal light-emitting diodes. Science 295, 1506–1508 (2002).

    ADS  Article  Google Scholar 

  8. 8.

    Borek, C. et al. Highly efficient, near-infrared electrophosphorescence from a Pt–metalloporphyrin complex. Angew. Chem. Int. Ed. 46, 1109–1112 (2007).

    Article  Google Scholar 

  9. 9.

    Cocchi, M., Kalinowski, J., Virgili, D. & Williams, J. A. G. Excimer-based red/near-infrared organic light-emitting diodes with very high quantum efficiency. Appl. Phys. Lett. 92, 113302 (2008).

    ADS  Article  Google Scholar 

  10. 10.

    Graham, K. R. et al. Extended conjugation platinum(ii) porphyrins for use in near-infrared emitting organic light emitting diodes. Chem. Mater. 23, 5305–5312 (2011).

    Article  Google Scholar 

  11. 11.

    Barbieri, A., Bandini, E., Monti, F., Praveen, V. K. & Armaroli, N. The rise of near-infrared emitters: organic dyes, porphyrinoids and transition metal complexes. Top. Curr. Chem. 374, 47 (2016).

    Article  Google Scholar 

  12. 12.

    Ai, X. et al. Efficient radical-based light-emitting diodes with doublet emission. Nature 563, 536–540 (2018).

    ADS  Article  Google Scholar 

  13. 13.

    Zhang, Y. et al. Near-infrared emitting materials via harvesting triplet excitons: molecular design, properties and application in organic light emitting diodes. Adv. Opt. Mater. 6, 1800466 (2018).

    Article  Google Scholar 

  14. 14.

    Özçelik, S. & Akins, D. L. Superradiance of aggregated thiacarbocyanine molecules. J. Phys. Chem. B 103, 8926–8929 (1999).

    Article  Google Scholar 

  15. 15.

    Arias, D. H. et al. Thermally-limited exciton delocalization in superradiant molecular aggregates. J. Phys. Chem. B 117, 4553–4559 (2013).

    Article  Google Scholar 

  16. 16.

    Cai, K., Xie, J. & Zhao, D. NIR J-aggregates of hydroazaheptacene tetraimides. J. Am. Chem. Soc. 136, 28–31 (2014).

    Article  Google Scholar 

  17. 17.

    Qian, G. et al. Simple and efficient near-infrared organic chromophores for light-emitting diodes with single electroluminescent emission above 1,000 nm. Adv. Mater. 21, 111–116 (2009).

    Article  Google Scholar 

  18. 18.

    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 

  19. 19.

    Klaus, D. R., Keene, M., Silchenko, S., Berezin, M. & Gerasimchuk, N. 1D polymeric platinum cyanoximate: a strategy toward luminescence in the near-infrared region beyond 1,000 nm. Inorg. Chem. 54, 1890–1900 (2015).

    Article  Google Scholar 

  20. 20.

    Ly, K. T. et al. Near-infrared organic light-emitting diodes with very high external quantum efficiency and radiance. Nat. Photon. 11, 63–68 (2017).

    ADS  Article  Google Scholar 

  21. 21.

    Zhang, Y. et al. Achieving NIR emission for donor–acceptor type platinum(ii) complexes by adjusting coordination position with isomeric ligands. Inorg. Chem. 57, 14208–14217 (2018).

    Article  Google Scholar 

  22. 22.

    Yam, V. W.-W., Wong, K. M.-C. & Zhu, N. Solvent-induced aggregation through metal···metal/π···π interactions: large solvatochromism of luminescent organoplatinum(ii) terpyridyl complexes. J. Am. Chem. Soc. 124, 6506–6507 (2002).

    Article  Google Scholar 

  23. 23.

    Yu, C., Wong, K. M.-C., Chan, K. H.-Y. & Yam, V. W.-W. Polymer-induced self-assembly of alkynylplatinum(ii) terpyridyl complexes by metal–metal/pi–pi interactions. Angew. Chem. Int. Ed. 44, 791–794 (2005).

    Article  Google Scholar 

  24. 24.

    Wong, K. M.-C. & Yam, V. W.-W. Self-assembly of luminescent alkynylplatinum(ii) terpyridyl complexes: modulation of photophysical properties through aggregation behavior. Acc. Chem. Res. 44, 424–434 (2011).

    Article  Google Scholar 

  25. 25.

    Hong, Y., Lam, J. W. Y. & Tang, B. Z. Aggregation-induced emission. Chem. Soc. Rev. 40, 5361–5388 (2011).

    Article  Google Scholar 

  26. 26.

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

    ADS  Article  Google Scholar 

  27. 27.

    Herrera, F. & Spano, F. C. Cavity-controlled chemistry in molecular ensembles. Phys. Rev. Lett. 116, 238301 (2016).

    ADS  Article  Google Scholar 

  28. 28.

    Spano, F. C., Silvestri, L., Spearman, P., Raimondo, L. & Tavazzi, S. Reclassifying exciton–phonon coupling in molecular aggregates: evidence of strong nonadiabatic coupling in oligothiophene crystals. J. Chem. Phys. 127, 184703 (2007).

    ADS  Article  Google Scholar 

  29. 29.

    Spano, F. C. The spectral signatures of Frenkel polarons in H- and J-aggregates. Acc. Chem. Res. 43, 429–439 (2010).

    Article  Google Scholar 

  30. 30.

    Spano, F. C. & Yamagata, H. Vibronic coupling in J-aggregates and beyond: a direct means of determining the exciton coherence length from the photoluminescence spectrum. J. Phys. Chem. B 115, 5133–5143 (2011).

    Article  Google Scholar 

  31. 31.

    Chen, W.-C., Chou, P.-T. & Cheng, Y.-C. Low internal reorganization energy of the metal–metal-to-ligand charge transfer emission in dimeric Pt(ii) complexes. J. Phys. Chem. C 123, 10225–10236 (2019).

    Article  Google Scholar 

  32. 32.

    Hestand, N. J. & Spano, F. C. Interference between Coulombic and CT-mediated couplings in molecular aggregates: H- to J-aggregate transformation in perylene-based π-stacks. J. Chem. Phys. 143, 244707 (2015).

    ADS  Article  Google Scholar 

  33. 33.

    Yersin, H., Rausch, A. F., Czerwieniec, R., Hofbeck, T. & Fischer, T. The triplet state of organo-transition metal compounds. Triplet harvesting and singlet harvesting for efficient OLEDs. Coord. Chem. Rev. 255, 2622–2652 (2011).

    Article  Google Scholar 

  34. 34.

    Li, K. et al. Highly phosphorescent platinum(ii) emitters: photophysics, materials and biological applications. Chem. Sci. 7, 1653–1673 (2016).

    Article  Google Scholar 

  35. 35.

    Hutchison, G. R., Ratner, M. A. & Marks, T. J. Hopping transport in conductive heterocyclic oligomers: reorganization energies and substituent effects. J. Am. Chem. Soc. 127, 2339–2350 (2005).

    Article  Google Scholar 

  36. 36.

    Robinson, G. W. & Frosch, R. P. Electronic excitation transfer and relaxation. J. Phys. Chem. 38, 1187–1203 (1963).

    Article  Google Scholar 

  37. 37.

    Wysokiński, R., Hernik, K., Szostak, R. & Michalska, D. Electronic structure and vibrational spectra of cis-diammine(orotato)platinum(ii), a potential cisplatin analogue: DFT and experimental study. Chem. Phys. 333, 37–48 (2007).

    Article  Google Scholar 

  38. 38.

    Juliá, F. & González-Herrero, P. Aromatic C–H activation in the triplet excited state of cyclometalated platinum(ii) complexes using visible light. J. Am. Chem. Soc. 138, 5276–5282 (2016).

    Article  Google Scholar 

  39. 39.

    Podeszwa, R., Bukowski, R. & Szalewicz, K. Potential energy surface for the benzene dimer and perturbational analysis of π–π interactions. J. Phys. Chem. A 110, 10345–10354 (2006).

    Article  Google Scholar 

  40. 40.

    Pullerits, T., Chachisvilis, M. & Sundström, V. Exciton delocalization length in the B850 antenna of Rhodobacter sphaeroides. J. Phys. Chem. 100, 10787–10792 (1996).

    Article  Google Scholar 

  41. 41.

    Chesnut, D. B. & Suna, A. Fermion behavior of one‐dimensional excitons. J. Chem. Phys. 39, 146–149 (1963).

    ADS  Article  Google Scholar 

  42. 42.

    van Burgel, M., Wiersma, D. A. & Duppen, K. The dynamics of one‐dimensional excitons in liquids. J. Chem. Phys. 102, 20–33 (1995).

    ADS  Article  Google Scholar 

  43. 43.

    Kim, K.-H. et al. Crystal organic light-emitting diodes with perfectly oriented non-doped Pt-based emitting layer. Adv. Mater. 28, 2526–2532 (2016).

    Article  Google Scholar 

  44. 44.

    Sommer, J. R. et al. Efficient near-infrared polymer and organic light-emitting diodes based on electrophosphorescence from (tetraphenyltetranaphtho[2,3]porphyrin)platinum(ii). ACS Appl. Mater. Interfaces 1, 274–278 (2009).

    Article  Google Scholar 

  45. 45.

    Nagata, R., Nakanotani, H. & Adachi, C. Near-infrared electrophosphorescence up to 1.1 µm using a thermally activated delayed fluorescence molecule as triplet sensitizer. Adv. Mater. 29, 1604265 (2017).

    Article  Google Scholar 

  46. 46.

    Kim, D.-H. et al. High-efficiency electroluminescence and amplified spontaneous emission from a thermally activated delayed fluorescent near-infrared emitter. Nat. Photon. 12, 98–104 (2018).

    ADS  Article  Google Scholar 

  47. 47.

    Minotto, A. et al. Efficient near-infrared electroluminescence at 840 nm with ‘metal-free’ small-molecule:polymer blends. Adv. Mater. 30, 1706584 (2018).

    Article  Google Scholar 

  48. 48.

    Chang, C.-H. et al. A new class of sky-blue-emitting Ir(iii) phosphors assembled using fluorine-free pyridyl pyrimidine cyclometalates: application toward high-performance sky-blue- and white-emitting OLEDs. ACS Appl. Mater. Interfaces 5, 7341–7351 (2013).

    Article  Google Scholar 

  49. 49.

    Liu, X. et al. Syntheses, crystal structure and photophysical property of iridium complexes with 1,3,4-oxadiazole and 1,3,4-thiadiazole derivatives as ancillary ligands. J. Organomet. Chem. 785, 11–18 (2015).

    Article  Google Scholar 

Download references


This research was supported by funding from the Ministry of Science and Technology (MOST), the Featured Areas Research Program within the framework of the Higher Education Sprout Project administered by the Ministry of Education (MOE), National Taiwan University, Soochow University and the Research Grant Council and City University of Hong Kong. We are also grateful to the National Center for High-Performance Computing (NCHC) and National Synchrotron Radiation Research Center (NSRRC) for computer time and facilities, respectively.

Author information




Y.-C.W., D.-G.C., K.-H.C., C.-W.W. and S.-H.L. performed optical measurements, simulations and calculations. S.F.W., W.-H.C. and J.-L.L. conducted the synthesis and characterization of Pt(ii) complexes. Y.H., L.-S.L. and W.-Y.H. executed OLED fabrications and analysed data. Y.-C.W. and P.-T.Chou developed the theoretical approach and prepared the manuscript. Y.C. designed the Pt(ii) complexes and interpreted the spectroscopic data. T.-H.W., P.-T.Chen and H.-F.H. performed GIXD experiments and data analysis. All authors discussed the results and contributed to the manuscript.

Corresponding authors

Correspondence to Liang-Sheng Liao or Yun Chi or Pi-Tai Chou.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–11 and Tables 1–5.

Crystallographic Data

Crystal structure of 4dMp.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Wei, Y., Wang, S.F., Hu, Y. et al. Overcoming the energy gap law in near-infrared OLEDs by exciton–vibration decoupling. Nat. Photonics (2020). https://doi.org/10.1038/s41566-020-0653-6

Download citation