This review highlights the opportunities and challenges in stability of organic solar cells arising from the emergence of non-fullerene acceptors.

Environmental stability is a common challenge for the commercialisation of low cost, encapsulation-free organic opto-electronic devices.

Surface passivation in perovskite solar cells can enhance device efficiency, yet incomplete interfacial functionality poses challenges to long-term reliability. Here we present a strategic interfacial engineering approach using sodium heptafluorobutyrate to fully functionalize the perovskite surface. Sodium heptafluorobutyrate acts as an ion shield that tunes the perovskite surface work function and increases the defect formation energy, resulting in an improved interface with the electron transport layer that minimizes recombination and boosts electron extraction under operation. We find that a sodium-heptafluorobutyrate-functionalized perovskite surface promotes a uniform, compact C ₆₀ layer that effectively blocks ion diffusion and stabilizes the device stack. This approach allows p–i–n perovskite solar cells to achieve a record power conversion efficiency (PCE) of 27.02% (certified 26.96% with a maximum-power-point-tracking PCE of 26.61%). Devices with an active area of 1 cm ² deliver a PCE of 25.95%. Perovskite solar cells retain 100% of their initial efficiency following 1,200 h of continuous 1-sun illumination at the maximum power point. Devices also demonstrate exceptional thermal stability, retaining 92% of the initial PCE when ageing at 85 °C for 1,800 h and 94% after 200 thermal cycles between –40 °C and +85 °C.

With the emergence of non-fullerene electron acceptors resulting in further breakthroughs in the performance of organic solar cells, there is now an urgent need to understand their degradation mechanisms in order to improve their intrinsic stability through better material design. In this study, we present quantitative evidence for a common root cause of light-induced degradation of polymer:non-fullerene and polymer:fullerene organic solar cells in air, namely a fast photo-oxidation process of the photoactive materials mediated by the formation of superoxide radical ions, whose yield is found to be strongly controlled by the lowest unoccupied molecular orbital (LUMO) levels of the electron acceptors used. Our results elucidate the general relevance of this degradation mechanism to both polymer:fullerene and polymer:non-fullerene blends and highlight the necessity of designing electron acceptor materials with sufficient electron affinities to overcome this challenge, thereby paving the way toward achieving long term solar cell stability with minimal device encapsulation.

Recent progress in the development of OPVs, PPVs and QDPVs for indoor applications.