Triplet Acceptors with a D‐A Structure and Twisted Conformation for Efficient Organic Solar Cells

Autor: Kai Wang, Yuhao Li, Hui Huang, Yuanping Yi, Lei Yang, Xiaoxi Wu, Jianwei Yu, Miaofei Huang, Xin Zhang, Feng Gao, Kangwei Wang, Hao Chen, Xingzheng Liu, Jianlong Xia, Linqing Qin, Xinhui Lu, Fenggui Zhao
Jazyk: angličtina
Rok vydání: 2020
Předmět:
Zdroj: Angewandte Chemie (International Ed. in English)
ISSN: 1521-3773
1433-7851
Popis: Triplet acceptors have been developed to construct high‐performance organic solar cells (OSCs) as the long lifetime and diffusion range of triplet excitons may dissociate into free charges instead of net recombination when the energy levels of the lowest triplet state (T1) are close to those of charge‐transfer states (3CT). The current triplet acceptors were designed by introducing heavy atoms to enhance the intersystem crossing, limiting their applications. Herein, two twisted acceptors without heavy atoms, analogues of Y6, constructed with large π‐conjugated core and D‐A structure, were confirmed to be triplet materials, leading to high‐performance OSCs. The mechanism of triplet excitons were investigated to show that the twisted and D‐A structures result in large spin–orbit coupling (SOC) and small energy gap between the singlet and triplet states, and thus efficient intersystem crossing. Moreover, the energy level of T1 is close to 3CT, facilitating the split of triplet exciton to free charges.
Triplet materials are designed by introducing heavy atoms to enhance spin–orbit coupling or constructing donor and acceptor units with a twisted conformation to reduce ΔE ST. However, the twisted materials have not been applied in solar cells due to weak absorption and low charge‐transport mobilities. Now two nonplanar acceptors with large π‐conjugated core were constructed that achieved over 15 % efficiency.
Databáze: OpenAIRE
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