Homogenizing Electron and Hole Transport Layers in Tin Perovskite Solar Cells to Enhance Photocurrent and Voltage

Tin perovskite solar cells (TPSCs) are considered as a sustainable alternative to their lead-containing counterparts, offering an ideal bandgap, a more stable crystal structure, and better semiconducting properties. However, the fabrication of efficient and able TPSCs has been a challenging task. Among the main components of TPSCs, herein, we investigated the transport layers and their interface with the perovskite layer. Several microscopy techniques revealed inhomogeneity in the common hole transport layer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and the electron transport layer (ETL), indene-C₆₀ bisadduct (ICBA). A hydrogen-bond donor molecule d-sorbitol modified the microstructure of PEDOT:PSS, increasing its conductivity and the crystallization density of the overlying perovskite layer. Blending 1% poly(methyl methacrylate) into ICBA rendered a uniform ETL, which facilitated electron transport across its interface with tin perovskite. The photocurrent density, open-circuit voltage, and fill factor of the TPSCs were all enhanced to achieve a power conversion efficiency of 15.8% and excellent short-term stability. Our findings address an often-neglected aspect of device fabrication and provide a new approach to boosting the performance and reproducibility of TPSCs.