UV-Blocking and Transparent Polydimethylsiloxane Film for Improving Stability of Perovskite Photovoltaics

Long-term stability of high-power conversion efficiency (PCE) against UV degradation is imperative to commercialize organometallic halide perovskite solar cells (PSCs). This degradation problem can be solved by blocking UV light, but it leads to a decrease in the PCE due to the decrease in the total amount of absorbed light in the PSC devices. Here, we propose a facile strategy for this challenging problem by attaching textured and UV-blocking bilayer PDMS films with a gradient refractive index onto the glass of PSC devices. We fabricated a gradient-refractive-indexed PDMS film by adopting a two-layer structure─a pure PDMS layer and a UV blocker (2,2′-dihydroxy-4-methoxy benzophenone)-added PDMS layer. The two-layer structure of PDMS films blocked the UV region (>380 nm) and increased the average transmittance by 1.8% at 600–800 nm due to the gradient refractive index. Additionally, the two-layered PDMS films were surface-textured by pattern replication from chemically etched Si surfaces. Surface texturing improved the average transmittance by 4.11% in the visible region as compared to that for the pure-flat PDMS film. The final PDMS film exhibited blocking of light >380 nm and enhanced absorption in the 400–800 nm region. As a result, MAPbI3 PSCs with a surface-textured bilayer PDMS film showed 0.8% higher PCE than did pristine devices. The PCE of the encapsulated device maintained over 90% of its initial performance after 240 h at 55% relative humidity under outdoor conditions and delivered 87% device performance even with additional UV irradiation after 240 h.