Mohamed Samir

In this study, we introduce the vapor‐induced donor–acceptor interface (VIDAI) method to enhance the performance of bilayer organic solar cells (OSCs) through direct solvent vapor treatment at the donor–acceptor interface. Using the inverted device structure ITO/ZnO/D18/Y6/MoO₃/Ag, we applied 1‐chloronaphthalene (CN) and 1,8‐diiodooctane (DIO) vapors directly to the donor layer to treat the interface between the D18 and Y6 layers. Compared to the nontreated devices, the devices incorporating VIDAI demonstrated improvements in power conversion efficiency (PCE) under 1 sun illumination from 15.1% to 16.8% and 17.0% for CN and DIO, respectively, and for indoor illumination from 13.2% to 14.9% and 15.0% for CN and DIO, respectively. This is attributed to optimized surface tension and improved recombination lifetime. Additionally, the VIDAI method enhanced device stability, with the DIO‐treated device exhibiting the highest maximum power point stability. This work establishes VIDAI as a simple, and effective, strategy for optimizing the efficiency and stability of bilayer OSCs, paving the way for their application in both outdoor and indoor energy harvesting.

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.

Organic photovoltaic (OPV) cells have experienced significant development in the last decades after the introduction of nonfullerene acceptor molecules with top power conversion efficiencies reported over 19% and considerable versatility, for example, with application in transparent/semitransparent and flexible photovoltaics. Yet, the optimization of the operational stability continues to be a challenge. This study presents a comprehensive investigation of the use of a conjugated polyelectrolyte polymer (CPE-Na) as a hole layer (HTL) to improve the performance and longevity of OPV cells. Two different fabrication approaches were adopted: integrating CPE-Na with PEDOT:PSS to create a composite HTL and using CPE-Na as a stand-alone bilayer deposited beneath PEDOT:PSS on the ITO substrate. These configurations were compared against a reference device employing PEDOT:PSS alone, as the HTL increased efficiency and fill factor. The instruments with CPE-Na also demonstrated increased stability in the dark and under simulated operational conditions. Device-based PEDOT:PSS as an HTL reached T80 after 2500 h while involving CPE-Na in the device kept at T90 in the same period, evidenced by a reduced degradation rate. Furthermore, the impedance spectroscopy and photoinduced transient methods suggest optimized charge transfer and reduced charge carrier recombination. These findings collectively highlight the potential of CPE-Na as a HTL optimizer material for nonfluorine OPV cells.

At present, low long-term stability is the main limitation for organic solar cells. The origin of the degradation of high-efficiency non-fullerene solar cells by impedance spectroscopy and its degradation mechanisms has been investigated.