Emerging Chemistry in Enhancing the Chemical and Photochemical Stabilities of Fused‐Ring Electron Acceptors in Organic Solar Cells

Abstract

The power conversion efficiency of organic solar cells (OSCs) has made exceptionally rapid progress in the past five years owing to the emergence of fused-ring electron acceptors (FREAs). To achieve the commercialization, it is urgent to resolve the stability issues of OCSs from materials to devices. In particular, the state-of-the-art FREAs, often synthesized by Knoevenagel condensation, generally contain two exocyclic vinyl groups (CC bond) as the conjugated bridges, which inevitably exhibit an obvious electron-deficient characteristic due to the strong push-pull electronic effect. As a result, these vinyl bridges are vulnerable to nucleophile attacking and/or photooxidation, leading to poor chemical and photochemical stabilities of FREAs that easily cause the degradation of device performance. In this perspective, an in-depth understanding of the degradation mechanism of FREAs is provided, and then effective strategies reported recently are reviewed for improving the chemical and photochemical stabilities of FREAs from interfacial engineering to molecular engineering to additive engineering. Finally, a conclusion and outlook for the future design of highly efficient and stable FREAs are also presented.

Traps and transport resistance are the next frontiers for stable non-fullerene acceptor solar cells

“…A reasonable degradation mechanism featuring a J sc loss only is the recombination of excited triplet excitons to the ground state by simultaneously exciting an oxygen molecule. Those oxygen radicals have been identified as the precursor of chemical reactions in a polymer:NFA solar cell leading to photobleaching and, thus, to J sc losses 8 , 14 , 22 , 23 . The second degradation pathway is characterized by losses of V oc and particularly FF, and is observed whenever the device under test is aged thermally.…”

Recent progress in organic solar cells based on non-fullerene acceptors: materials to devices

“…Since organic materials are easily degraded by external factors, such as oxygen, light, and heat, various strategies for stable operation of OSCs based on NFAs have been proposed depending on the type of stress. 255…”

On the interface reactions and stability of nonfullerene organic solar cells

“…In the past four years, we have gained an understanding of the interface interaction and developed methods of manipulating the interactions. [41][42][43][44][45][46][47][48][49][50][51] In this perspective, rst, we will describe and discuss the phenomena and mechanism of the interactions between the nonfullerene active layer and interfacial layer from the view of the chemical structure and electronic properties; methods to test and analyze the chemical stability of NFAs will be discussed. Second, strategies of designing a chemically stable nonfullerene active layer or electron transporting layer and Fig.…”

“…In the past four years, we have gained an understanding of the interface interaction and developed methods of manipulating the interactions. 41–51…”