Efficient perovskite solar modules enabled by a UV-stable and high-conductivity hole transport material

Ultraviolet (UV) radiation poses a substantial challenge to the stability of prevalent p-i-n (positive-intrinsic-negative) perovskite solar cells (PSCs), demanding more robust hole-transport layers (HTLs) due to light incident from the HTL side. Here, we unveil that commonly used self-assembled monolayer (SAM)-type HTLs suffer from poor UV stability that causes irreversible damage to hole extraction and impairs device stability. To address this issue, we develop a polymeric and UV-stable HTL named Poly-2PACz, which exhibits strong binding to substrates and exceptional UV resistance over SAM-type HTLs. The PSCs blade-coated under ambient conditions using Poly-2PACz HTL achieved a remarkable efficiency of 26.0% and outstanding UV stability. Our cells retain 80% of the initial PCE even after about 500 hours of high-intensity UV illumination [7.7 times higher than that of air mass 1.5 global (AM 1.5G) solar spectrum]. Furthermore, Poly-2PACz exhibits good wettability and high conductance, enabling the fabrication of blade-coated minimodules with an aperture efficiency of 22.2% and excellent uniformity.