Isomerization of Perylene Diimide Based Acceptors Enabling High-Performance Nonfullerene Organic Solar Cells with Excellent Fill Factor.

Zhenghui Luo,Guangye Zhang,Yanming Sun,He Yan,Cheng Zhong,Chuluo Yang,Yiqun Xiao,Tao Liu,Zhanxiang Chen,Lijun Huo,Xinhui Lu

doi:10.1002/advs.201802065

Abstract

A strategy that employs the central‐core regiochemistry to develop two isomeric perylene diimide (PDI)‐based small molecular acceptors (SMAs), BPT‐Se and BPT‐Se1, is introduced, and the effect of the central‐core regiochemistry on the optical, electronic, charge‐transport, photovoltaic, and morphological properties of the molecules and their devices is investigated. The PDBT‐T1:BPT‐Se1‐based device delivers a power conversion efficiency (PCE) of 9.54% with an excellent fill factor (FF) of 73.2%, while the BPT‐Se‐based device yields a PCE of 7.78%. The large improvement of PCE upon isomerization of BPT‐Se should be ascribed to the concurrent enhancement of FF, short circuit current ( J SC), and open circuit voltage (V OC) of the PDBT‐T1:BPT‐Se1 devices. The higher FF of the organic solar cells (OSCs) based on PDBT‐T1:BPT‐Se1 can be attributed to the higher charge dissociation and charge collection efficiency, less bimolecular combination, more balanced µ h/µ e, better molecular packing and a more favorable morphology. It is worth mentioning that the FF of 73.2% is the highest value for PDI‐based SMAs OSCs to date. The result shows that regiochemistry of the central core in PDI‐based SMAs greatly affects the physicochemical properties and photovoltaic performance. The success of the isomerization strategy offers exciting prospects for the molecular design of PDI‐based SMAs.

Highlights

A strategy that employs the central-core regiochemistry to develop two isomeric perylene diimide (PDI)-based small molecular acceptors (SMAs), BPT-Se and BPT-Se1, is introduced, and the effect of the central-core regiochemistry on the optical, electronic, charge-transport, photovoltaic, and morphological properties of the molecules and their devices is investigated
Along with the device characterization, grazing incident X-ray wide-angle scattering (GIWAXS), and atomic force microscopy (AFM) studies explained the device performance trend and are consistent with our structural design expectation. These results indicate that isomerization can serve as another important route to regulate the molecular properties of the PDI-based acceptors and improve the photovoltaic performance of PDI-based nonfullerene organic solar cells (OSCs)
The absorption profiles of these SMAs are complementary to the strong absorption of PDBT-T1, the highly efficient polymer donor we reported previously that absorbs strongly in the range of 500–700 nm.[65]

Summary

Introduction

A strategy that employs the central-core regiochemistry to develop two isomeric perylene diimide (PDI)-based small molecular acceptors (SMAs), BPT-Se and BPT-Se1, is introduced, and the effect of the central-core regiochemistry on the optical, electronic, charge-transport, photovoltaic, and morphological properties of the molecules and their devices is investigated. These results indicate that isomerization can serve as another important route to regulate the molecular properties of the PDI-based acceptors and improve the photovoltaic performance of PDI-based nonfullerene OSCs. The synthetic routes to BPT-Se and BPT-Se1 are illustrated in Scheme 1 and Scheme S1 in the Supporting Information.

Results

Conclusion