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Correlating the Hybridization of Local‐Exciton and Charge‐Transfer States with Charge Generation in Organic Solar Cells

Deping Qian Orcid Logo, Saied Md Pratik, Qi Liu, Yifan Dong, Rui Zhang, Jianwei Yu, Nicola Gasparini, Jiaying Wu, Tiankai Zhang, Veaceslav Coropceanu, Xia Guo, Maojie Zhang, Jean‐Luc Bredas, Feng Gao, James Durrant

Advanced Energy Materials, Volume: 13, Issue: 32, Start page: 2301026

Swansea University Author: James Durrant

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DOI (Published version): 10.1002/aenm.202301026

Abstract

In organic solar cells with very small energetic‐offset (ΔELE − CT), the charge‐transfer (CT) and local‐exciton (LE) states strongly interact via electronic hybridization and thermal population effects, suppressing the non‐radiative recombination. Here, we investigated the impact of these effects on...

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Published in: Advanced Energy Materials
ISSN: 1614-6832 1614-6840
Published: Wiley 2023
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa70701
Abstract: In organic solar cells with very small energetic‐offset (ΔELE − CT), the charge‐transfer (CT) and local‐exciton (LE) states strongly interact via electronic hybridization and thermal population effects, suppressing the non‐radiative recombination. Here, we investigated the impact of these effects on charge generation and recombination. In the blends of PTO2:C8IC and PTO2:Y6 with very small, ultra‐fast CT state formation was observed, and assigned to direct photoexcitation resulting from strong hybridization of the LE and CT states (i.e., LE‐CT intermixed states). These states in turn accelerate the recombination of both CT and charge separated (CS) states. Moreover, they can be significantly weakened by an external‐electric field, which enhanced the yield of CT and CS states but attenuated the emission of the device. This study highlights that excessive LE‐CT hybridization due to very low , whilst enabling direct and ultrafast charge transfer and increasing the proportion of radiative versus non‐radiative recombination rates, comes at the expense of accelerating recombination losses competing with exciton‐to‐charge conversion process, resulting in a loss of photocurrent generation.
Keywords: charge generation, hybridization, non-radiative voltage loss, organic solar cells
College: Faculty of Science and Engineering
Funders: Swedish Research Council VR (Grant Number: 2019-00677); National Natural Science Foundation of China (NSFC) (Grant Number: 51973146); Shandong Provincial Natural Science Foundation (Grant Number: ZR2022JQ09); Collaborative Innovation Center of Suzhou Nano Science & Technology; EPSRC project ATIP (Grant Number: EP/TO28513/1); Office of Naval Research (Grant Number: N00014-20-1-2110).
Issue: 32
Start Page: 2301026

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