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Suppressed recombination loss in organic photovoltaics adopting a planar–mixed heterojunction architecture

Kui Jiang (Co-first Author), Jie Zhang (Co-first Author), Cheng Zhong (Co-first Author), Francis R. Lin*, Feng Qi, Qian Li, Zhengxing Peng, Werner Kaminsky, Sei-Hum Jang, Jianwei Yu, Xiang Deng, Huawei Hu, Dong Shen, Feng Gao, Harald Ade, Min Xiao, Chunfeng Zhang*, Alex K.-Y. Jen*

*Corresponding author for this work

Research output: Journal Publications and Reviews › RGC 21 - Publication in refereed journal › peer-review

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Abstract

At present, high-performance organic photovoltaics mostly adopt a bulk-heterojunction architecture, in which exciton dissociation is facilitated by charge-transfer states formed at numerous donor–acceptor (D-A) heterojunctions. However, the spin character of charge-transfer states originated from recombination of photocarriers allows relaxation to the lowest-energy triplet exciton (T1) at these heterojunctions, causing photocurrent loss. Here we find that this loss pathway can be alleviated in sequentially processed planar–mixed heterojunction (PMHJ) devices, employing donor and acceptor with intrinsically weaker exciton binding strengths. The reduced D-A intermixing in PMHJ alleviates non-geminate recombination at D-A contacts, limiting the chance of relaxation, thus suppressing T1 formation without sacrificing exciton dissociation efficiency. This resulted in devices with high power conversion efficiencies of >19%. We elucidate the working mechanisms for PMHJs and discuss the implications for material design, device engineering and photophysics, thus providing a comprehensive grounding for future organic photovoltaics to reach their full promise.
Original languageEnglish
Pages (from-to)1076-1086
JournalNature Energy
Volume7
Issue number11
Online published14 Nov 2022
DOIs
Publication statusPublished - Nov 2022

Funding

The work has been supported by the sponsorship of the Lee Shau-Kee Chair 504 Professor (Materials Science) (A.K.Y.J.); the City University of Hong Kong under the APRC Grant 505 9380086 (A.K.Y.J.); the Innovation and Technology Commission of Hong Kong under the TCFS Grant 506 GHP/018/20SZ (A.K.Y.J.), and MRP Grant MRP/040/21X (A.K.Y.J.); the Environment and Ecology 507 Bureau of Hong Kong under the Green Tech Fund 202020164 (A.K.Y.J.); the US Office of Naval 508 Research under the grant numbers N00014-20-1-2191 (A.K.Y.J.), N000141712204 (Z.P. and H.A.), 509 and N000142012155 (Z.P. and H.A.); the Research Grants Council of Hong Kong under General 510 Research Fund 11307621 (A.K.Y.J.), the Collaborative Research Fund C6023-19GF (A.K.Y.J.), and 511 the Hong Kong Postdoctoral Fellowship Scheme (F.R.L.); the Guangdong Major Project of Basic and 512 Applied Basic Research under the grant number 2019B030302007 (A.K.Y.J.); the Guangdong-Hong 513 Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials under the grant 514 number 2019B121205002 (A.K.Y.J.); the National Key R&D Program of China under the grant 515 numbers 2017YFA0303703 (C. Zhang), and 2018YFA0209100 (C. Zhang); the Fundamental Research 516 Funds for the Central Universities under the grant number 0204-14380177 (C. Zhang); the National 517 Natural Science Foundation of China under the grant numbers 22225305 (C. Zhang), 21922302 (C. 518 Zhang), 21873047 (C. Zhang), 52002393 (J.Z.), and 51873160 (C. Zhong). The authors also gratefully 519 acknowledge Dr. H. Zhang and Prof. Z. Cai from the Hong Kong Baptist University for the 520 experimental assistances on MALDI-ToF measurements, and Prof. S. B. Jo from the Sungkyunkwan 521 University for his help on analyzing TA data.

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

  1. SDG 7 - Affordable and Clean Energy
    SDG 7 Affordable and Clean Energy

Publisher's Copyright Statement

  • COPYRIGHT TERMS OF DEPOSITED POSTPRINT FILE: This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: http://dx.doi.org/10.1038/s41560-022-01138-y.

RGC Funding Information

  • RGC-funded

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