Stability Of Non‐Fullerene Electron Acceptors and Their Photovoltaic Devices

Abstract

Non-fullerene electron acceptors (NFAs) are recognized as "rising star" in recent years in the organic solar cells (OSCs) community. In contrast to the traditional fullerene electron acceptors, NFAs promise superior feasibility in molecular design with tunable optoelectronic properties, experiencing unprecedented development in the last 5 years with maximum achievable power conversion efficiencies over 18% are acquired in NFA based OSCs. Nevertheless, the stability of NFAs and their OSCs is still problematic and not well understood, and is regarded as the bottleneck toward the commercialization of NFA based OSCs. In this review, recent advances and current understanding of the stability of NFAs and their corresponding OSCs are presented. Specifically, three key factors, including chemical-, photon-, and thermal-, induced degradations in NFAs are analyzed and summarized, with approaches to enhance the stability suggested. This is followed by the discussion of shelf and operational stability of NFA based OSCs, with highlights of operational stabilities in inert, ambient, indoor, and outdoor conditions. It is envisaged that operational lifetime of over 20 years in real world is achievable via the joint efforts from material design, morphology control, interfacial engineering, and encapsulation technology.

Recent advances of crosslinkable organic semiconductors in achieving solution-processed and stable optoelectronic devices

“…Similarly, molecular stacking and aggregation also occurs in non-fullerene acceptor systems under thermal conditions, affecting the stability of OPV devices. 90,91 Therefore, it is extremely crucial to enhance the stability of the photoactive layer morphology.…”

Boosting the Photovoltaic Performance and Thermal Stability of Organic Solar Cells via an Insulating Fluoropolymer Additive

“…In addition to the photovoltaic performance of devices, the thermal stability of OSCs has been received extensive attention recently. [44,45] Therefore, we further explored the thermal stability of PTFS additive processed devices comparing with the non-additive and the PS treated devices. The changing photovoltaic parameters of the corresponding devices were shown in Figure 8.…”

Stable dinitrile end-capped closed-shell non-quinodimethane as a donor, an acceptor and an additive for organic solar cells

“…46 Furthermore, most emerging NFAs containing 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (IC)-type terminals are synthesized by the Knoevenagel condensation reaction, which would make them prone to decompose under persistent light irritation. 47–53 It has been demonstrated that the photodegradation products of typical NFAs such as ITIC with IC end groups contain fused-ring isomers via a 6-e electrocyclic reaction between the dicyanomethylene unit and the thiophene ring. 50 A promising and efficient method is employing robust carbon–carbon bonds instead of the vulnerable exocyclic double bonds to link the donor unit and the acceptor unit of NFAs, which can not only lead to intrinsically stable acceptors but also successfully adjust the optoelectronic properties of NFAs.…”