Highly Efficient UV-Absorbing and Anti-Reflective PDMS Film for Improving Stability of Perovskite and Organic Photovoltaics.

Perovskite solar cells and polymer-based organic solar cells(OSCs) have emerged as promising next-generation solar cell technologies due to their high efficiency, utilization of low-cost materials, and large-area fabrication capabilities. Despite these advantages, the commercialization of these solar cells faces significant challenges, primarily concerning module reliability and lifespan. Notably, both perovskite solar cells and OSCs exhibit high sensitivity to the surrounding environment, including heat, moisture, and UV rays. Exposure to UV light has been identified as a cause of decomposition in perovskite solar cells, leading to the generation of ionized lead and interfacial separation. Additionally, UV light exposure has been associated with a burn-in phenomenon in organic solar cells. The importance of UV light blocking to prevent degradation has been reported through many research results.<br/>Hence, it is imperative to ensure stability against UV rays in order to successfully commercialize next-generation solar cells. Recently, the integration of UV-blocking materials into coatings and films has emerged as a promising strategy to address this issue of stability by effectively blocking UV light. Despite the significant improvement in a device, it leads to unavoidable photoconversion energy loss by blocking the UV region light. Consequently, the concept of blocking UV for stability requires additional techniques for keeping high photoconversion efficiency.<br/>To overcome the inherent problem in this concept, we suggest an easily detachable multifunctional film for UV blocking without photoconversion energy loss. The multifunctional film was fabricated by incorporating a UV-blocking material(2,2'-dihydroxy-4-methoxybenzophenone) with polydimethylsiloxane(PDMS). By incorporating a UV absorber into the PDMS film, we could successfully block UV region light(&lt; 380nm). As mentioned, the UV blocking induced the decrease of PCE of perovskite solar cells by 3.2% compared with reference cells. The decrease in PCE was compensated by the light-trapping effect from the surface texturing of the PDMS films. For the surface texturing, we used the soft lithography technique using a structured Si mold through Cu-assisted chemical etching. The light trapping effect was estimated by FDTD simulation and confirmed by the optical properties of textured films. The reflectance of structured PDMS decreased by ~ 4% compared with a flat PDMS surface. To increase the transmittance of the visible light region, we designed double-layered PDMS films, i.e., pure PDMS layer/UV block material embedded PDMS layer films. Our final multifunctional film was attached to the glass side of perovskite solar cells and showed 0.8% increased PCE compared with the reference cell. The UV-blocking effect was confirmed by 20 days test (10 days outdoor + 10 days UV irradiation ). The solar cells with multifunctional PDMS films retained over 87% of their initial efficiency after 20 days test, in contrast to the rapid UV degradation observed in solar cells without the UV-blocking PDMS film.