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Naphthodithiophene‐Based Nonfullerene Acceptor for High‐Performance Organic Photovoltaics: Effect of Extended Conjugation
Author(s) -
Zhu Jingshuai,
Ke Zhifan,
Zhang Qianqian,
Wang Jiayu,
Dai Shuixing,
Wu Yang,
Xu Ye,
Lin Yuze,
Ma Wei,
You Wei,
Zhan Xiaowei
Publication year - 2018
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201704713
Subject(s) - organic solar cell , materials science , acceptor , homo/lumo , energy conversion efficiency , electron acceptor , ring (chemistry) , band gap , yield (engineering) , open circuit voltage , electron mobility , absorption (acoustics) , optoelectronics , photochemistry , voltage , molecule , chemistry , organic chemistry , electrical engineering , polymer , physics , engineering , metallurgy , composite material , condensed matter physics
Naphtho[1,2‐ b :5,6‐ b′ ]dithiophene is extended to a fused octacyclic building block, which is end capped by strong electron‐withdrawing 2‐(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐inden‐1‐ylidene)malononitrile to yield a fused‐ring electron acceptor (IOIC2) for organic solar cells (OSCs). Relative to naphthalene‐based IHIC2, naphthodithiophene‐based IOIC2 with a larger π‐conjugation and a stronger electron‐donating core shows a higher lowest unoccupied molecular orbital energy level (IOIC2: −3.78 eV vs IHIC2: −3.86 eV), broader absorption with a smaller optical bandgap (IOIC2: 1.55 eV vs IHIC2: 1.66 eV), and a higher electron mobility (IOIC2: 1.0 × 10 −3 cm 2 V −1 s −1 vs IHIC2: 5.0 × 10 −4 cm 2 V −1 s −1 ). Thus, IOIC2‐based OSCs show higher values in open‐circuit voltage, short‐circuit current density, fill factor, and thereby much higher power conversion efficiency (PCE) values than those of the IHIC2‐based counterpart. In particular, as‐cast OSCs based on FTAZ: IOIC2 yield PCEs of up to 11.2%, higher than that of the control devices based on FTAZ: IHIC2 (7.45%). Furthermore, by using 0.2% 1,8‐diiodooctane as the processing additive, a PCE of 12.3% is achieved from the FTAZ:IOIC2 ‐ based devices, higher than that of the FTAZ:IHIC2 ‐ based devices (7.31%). These results indicate that incorporating extended conjugation into the electron‐donating fused‐ring units in nonfullerene acceptors is a promising strategy for designing high‐performance electron acceptors.