Completely annealing-free flexible Perovskite quantum dot solar cells employing UV-sintered Ga-doped SnO₂ electron transport layers

The electron transport layer (ETL) is a critical component in perovskite quantum dot (PQD) solar cells, significantly impacting their photovoltaic performance and stability. Low-temperature ETL deposition methods are especially desirable for fabricating flexible solar cells on polymer substrates. Herein, we propose a room-temperature-processed tin oxide (SnO₂) ETL preparation method for flexible PQD solar cells. The process involves synthesizing highly crystalline SnO₂ nanocrystals stabilized with organic ligands, spin-coating their dispersion, followed by UV irradiation. The energy level of SnO₂ is controlled by doping gallium ions to reduce the energy level mismatch with the PQD. The proposed ETL-based CsPbI₃-PQD solar cell achieves a power conversion efficiency (PCE) of 12.70%, the highest PCE among reported flexible quantum dot solar cells, maintaining 94% of the initial PCE after 500 bending tests. Consequently, we demonstrate that a systemically designed ETL enhances the photovoltaic performance and mechanical stability of flexible optoelectronic devices.