Breaking the Efficiency-Transparency Compromise in Semitransparent Solar Cells by Optimizing the Perovskite/C₆₀ Interface

Semitransparent perovskite solar cells (ST-PSCs) are emerging as promising candidates for tandem architectures and building integrated photovoltaics. However, their development is constrained by a large open-circuit voltage (<i>V</i>_OC) loss suffered from severe interfacial nonradiative recombination. Here, we propose surface molecular engineering employing tyramine hydrochloride (TACl) at the perovskite/C₆₀ interface to concurrently passivate interfacial defects and optimize the energy-level alignment. Organic ammonium ions selectively passivate Pb-related defects while chloride ions compensate halide vacancies, collectively suppressing nonradiative recombination loss. This molecular engineering yields a wide-bandgap perovskite film with enhanced crystallinity and minimized defect density, facilitating efficient charge extraction and improved open-circuit voltage. The target semitransparent device achieved a remarkable power conversion efficiency (PCE) of 14.66% with an average visible light transmittance of 13.2%. Notably, the TACl-modified ST-PSCs showed remarkably enhanced stability in an air environment (RH = 30 ± 5%), maintaining nearly 82% of their initial PCE values after 720 h of aging, far exceeding the 54% retention of the control device. This work establishes a promising strategy for defect passivation and energy-level optimization of high-performance semitransparent perovskite solar cells.