Improvement of stability and efficiency of tin-based perovskite solar cells with inclusion of Cu-Sn-graphene oxide composites in interfacial and active layers

Tin-based halide perovskite solar cells (Sn-PSCs) have attracted considerable attention as an alternative to lead-based perovskite solar cell. However, intrinsic Sn²⁺/Sn⁴⁺ oxidation and poor crystallinity reduces device efficiency and stability. To address the Sn²⁺ oxidation and instability issues, we synthesized the composites of Cu and Sn quantum dots (QDs) embedded on nitrogen-doped graphene oxide (NGO) sheets (i.e., Cu-Sn-NGO composites) and utilized them into interfacial layer (IL) and active layer (AL) of Sn-PSC. The composite-based perovskite films produced pinhole-free denser and thicker film having large grains. The inclusion of Cu-Sn-NGO in IL and AL yields better band alignment, reduces trap-state density, and suppresses recombination with fast charge conduction, leading to overall enhancement of device performance. Compared to reference Sn-PSC without Cu-Sn-NGO, the composites-based champion devices showed high reproducibility and dramatic enhancement of photovoltaic parameters (i.e., V_OC = 0.98 V, J_SC = 21.72 mA/cm², FF = 65.35 %, and PCE = 13.91 %) with sustaining long-term stability over 90 d and thermal and optical stability.