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Herein, a straightforward vacuum‐assisted method is introduced to enhance the stability of nonfullerene organic solar cells (OSCs). The method, termed "prevacuum" involves subjecting the active layer (D18:Y6) to a low‐pressure vacuum (−1 bar) before thermal annealing at 100 °C. Compared to untreated devices, prevacuum‐treated OSCs exhibit a notable increase in power conversion efficiency from 13.71% to 14.90%. This enhancement is attributed to improved light absorption and charge extraction, as evidenced by external quantum efficiency measurements. Moreover, prevacuum treatment significantly improves device stability under operational conditions, with a 30% power loss occurring after 8.25 h compared to 4.5 h for untreated devices. This improvement is attributed to the removal of volatile components and impurities during the vacuum process, leading to a more hydrophobic and stable active layer. The study demonstrates the efficacy of prevacuum treatment as a simple and accessible method for enhancing the performance and longevity of OSCs, paving the way for their broader application in sustainable energy technologies. [ABSTRACT FROM AUTHOR]

In this work, a comparative degradation analysis of high-efficiency inverted organic solar cells (iOSCs) is presented, with the PTB7-Th:PC70BM blend as the active layer and hole transport layers (HTLs), of V2O5, MoO3 and their stacks. Five groups of iOSCs, were fabricated with V2O5 (3 nm), V2O5/MoO3 (3/1 nm), V2O5/MoO3 (3/2 nm), V2O5/MoO3 (3/5 nm) and MoO3 (10 nm), respectively. The performance parameters obtained from illuminated J–V curves of the devices were analyzed. The long-term operational stability of encapsulated iOSCs is studied following the ISOS-D1 protocols for 19 600 h. The maximum PCE obtained using stacks of V2O5/MoO3 (3/1 nm) is 10.58%. The best stability was obtained for devices using 10 nm MoO3 as the HTL, for which after 19 600 h, the PCE reduced to 51%. The cell using 3 nm V2O5 degraded to 50% of its initial PCE (T50) after only 775 hours. The use of stacks of V2O5/MoO3 (3/1 nm), V2O5/MoO3(3/2 nm), V2O5/MoO3 (3/5 nm), increased the long-term stability of iOSCs, with T50 values equal to 3140 h, 4865 h, and 6808 h, respectively. Our study provides the details of the causes of the differences in behavior observed for the different materials used as HTLs. Although the physical degradation mechanism seems to be the same, the intensity is lower as the MoO3 thickness increases, which acts as a diffusion barrier reducing the diffusion rate of O2 and H2O toward the active layer. The impedance spectroscopy measurements confirm that, in this study, the degradation of the active layer is the main cause of decrease in performance of the device. [ABSTRACT FROM AUTHOR]