Semi‐Transparent Perovskite Solar Cells with High Light‐Utilisation Efficiency of 5.10% Fabricated Through Molecular Dipole Engineering

Abstract Semi‐transparent perovskite solar cells (ST‐PSCs) are promising components of tandem solar cells and building‐integrated photovoltaics. However, the development of high‐performance ST‐PSCs is hampered by the inherent trade‐off between the power conversion efficiency (PCE) and average visible transmittance (AVT). The light‐utilisation efficiency (LUE = PCE × AVT) is a widely used holistic performance metric of ST‐PSCs. Wide‐bandgap perovskite CsPbI 2 Br emerges as an ideal candidate for ST‐PSCs due to its high AVT (bandgap ≈1.9 eV) and theoretical open‐circuit voltage ( V OC ≈1.6 V), which ensures excellent AVT while potentially enables PCE improvement through V OC enhancement. Herein, 3,5‐difluoro‐benzamidine hydrochloride is introduced as a Lewis acid–base dipole molecular additive to effectively regulate the crystallization and minimize defect density of perovskite films via interactions between F − and Pb 2+ along with hydrogen bonding (N–H…I/Br) within the Pb[I/Br] 6 4− octahedra. This dual interaction also optimises the energy‐level alignment in ST‐PSCs, facilitating charge extraction at the interface and substantially reducing V OC losses. Consequently, the ST‐PSCs achieve one of the highest LUE of 5.10% (PCE = 16.32%, AVT = 31.22%) and exhibit exceptional thermal stability. The proposed strategy efficiently enhances the PCE of ST‐PSCs while maintaining a high AVT, thereby facilitating their practical applications.