Tingting Liu, Ryosuke Nishikubo, Atsushi Wakamiya, Akinori Saeki Saeki
The development of efficient, stable, lead-free tin-based perovskite solar cells (PSCs) is hindered by severe interfacial recombination and poor energy level alignment. Here, we report on the dual optimization of the interface between PEDOT:PSS and Sn-perovskite (PEA 0.1 FA 0.9 SnI 3 with 5 mol % excess GeI 2; PEA: phenylethylammonium; FA: formamidinium) layers by integrating vacuum treatment and interlayer engineering. Treating both the PEDOT:PSS and the Sn-based perovskite layers in 10 –4 Pa for an optimal amount of time increases the power conversion efficiency (PCE) by improving crystallinity and reducing energetic disorder. Further treatment of the PEDOT:PSS layer with optimal concentrations of PEAI or MeO-2PACz/Al 2 O 3 was identified as an improvement strategy as opposed to PEACl or PEABr. A comparative analysis revealed that PEAI and MeO-2PACz/Al 2 O 3 yielded the highest PCE (8.00%, compared to 6.78% for the control) due to enhanced optical absorption and photoluminescence intensity, reduced Urbach energies, improved interfacial wettability, and favorable decreases in the ionization potentials of the hole transport layer. Considering the performance and fabrication practicality, PEAI was ultimately selected as the most effective interlayer. These results underscore the synergistic advantages of combining a vacuum treatment and interfacial modification for efficient and stable Sn-based PSCs.