Organic solar cells (OSCs) based on nonfullerene acceptors (NFAs) have made significant breakthrough in their device performance, now achieving a power conversion efficiency of ≈18% for single junction devices, driven by the rapid development in their molecular design and device engineering in recent years. However, achieving long‐term stability remains a major challenge to overcome for their commercialization, due in large part to the current lack of understanding of their degradation mechanisms as well as the design rules for enhancing their stability. In this review, the recent progress in understanding the degradation mechanisms and enhancing the stability of high performance NFA‐based OSCs is a specific focus. First, an overview of the recent advances in the molecular design and device engineering of several classes of high performance NFA‐based OSCs for various targeted applications is provided, before presenting a critical review of the different degradation mechanisms identified through photochemical‐, photo‐, and morphological degradation pathways. Potential strategies to address these degradation mechanisms for further stability enhancement, from molecular design, interfacial engineering, and morphology control perspectives, are also discussed. Finally, an outlook is given highlighting the remaining key challenges toward achieving the long‐term stability of NFA‐OSCs.

The mark of 18% power conversion efficiency (PCE) was recently overcome by laboratoryscale organic solar cells (OSCs) thanks to the development of nonfullerene acceptors (NFAs). NFA-based solar cells show improved performance and stability compared with those of their fullerene-acceptor-based counterparts. However, only a few studies focus on scalable deposition techniques or roll-to-roll compatible processing, which is of paramount importance for the commercialization of the technology. Here, we report a simple and fast fabrication of slot-die-coated poly(3-hexylthiophene-2,5-diyl):(5Z,5'Z)-5,5'-{[7,7'-(4,4,9,9-tetraoctyl-4,9-dihydro-s-indaceno[1,2-b:5, 6-b']dithiophene-2,7-diyl)bis(benzo[c][1,2,5]thiadiazole-7,4-diyl)]bis(methanylylidene)}bis(3-ethyl-2-thi oxothiazolidin-4-one) (P3HT:O-IDTBR) OSCs using a roll platform on flexible ITO-free substrates under ambient conditions. We show that the optical band gap of the active layer increases when an isopropanoldiluted poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) hole-transport layer is coated on top of it, changing the device properties. Optimization of the coating conditions leads to the achievement of up to 3.6% PCE for single cells of 1 cm 2 fabricated under ambient conditions with flexographic printed Ag back electrodes, compared with solar cells with evaporated Ag (3.8% PCE), Au (2.1% PCE), or Cu (3.0% PCE) back contacts. OSCs with larger areas of 4 cm 2 with 2.3% PCE are also fabricated, where the fast increase of the series resistance with the area is the main PCE-limiting factor. The efficiencies herein reported for NFAs obtained by roll processing show the excellent potential of the P3HT:O-IDTBR blend for large-scale fabrication.

With the advent of nonfullerene acceptors (NFAs), organic photovoltaic (OPV) devices are now achieving high enough power conversion efficiencies (PCEs) for commercialization. However, these high performances rely on active layers processed from petroleum-based and toxic solvents, which are undesirable for mass manufacturing. Here, we demonstrate the use of biorenewable 2-methyltetrahydrofuran (2MeTHF) and cyclopentyl methyl ether (CPME) solvents to process donor: NFA-based OPVs with no additional additives in the active layer. Furthermore, to reduce the overall carbon footprint of the manufacturing cycle of the OPVs, we use polymeric donors that require a few synthetic steps for their synthesis, namely, PTQ10 and FO6-T, which are blended with the Y-series NFA Y12. High performance was achieved using 2MeTHF as the processing solvent, reaching PCEs of 14.5% and 11.4% for PTQ10:Y12 and FO6-T:Y12 blends, respectively. This work demonstrates the potential of using biorenewable solvents without additives for the processing of OPV active layers, opening the door to large-scale and green manufacturing of organic solar cells.

Organic solar cells (OSCs) have increased their power conversion efficiency above 18% thanks to the use of non-fullerene acceptors in binary or ternary blends or in tandem configurations. In this article, a study on the lifetime of P3HT:O-IDTBR bulk heterojunction OSCs on ITO-free flexible substrates is presented. A direct comparison of glass–glass and plastic–plastic encapsulation performance, with a special focus on its effect on the lifetime of the devices after degradation procedures, has been carried out complying with the ISOS protocols for organic photovoltaic devices. The manufactured OSCs with 1 cm2 active layer have power conversion efficiencies ranging from 1.9 to 3.4% depending on the encapsulant material, encapsulation process, and substrate. An exponential degradation rate has been found, with a similar functional behavior for glass and plastic differing in the degradation constants, which ranges from k = 0.01 to 0.002 h−1. Only in one case, the ISOS-T3 essay for plastic encapsulation, a double exponential process, was observed with degradation rates of k1 = 0.03 h−1 and a second slower process with k2 = 0.001 h−1. The longest achieved T80 lifetime is 86 h for glass-encapsulated devices under an accelerated ISOS-T3 protocol.