Composite electron transport layer for efficient N-I-P type monolithic perovskite/silicon tandem solar cells with high open-circuit voltage

Perovskite/silicon tandem solar cells (PSTSCs) have exhibited huge technological potential for breaking the Shockley-Queisser limit of single-junction solar cells. The efficiency of P-I-N type PSTSCs has surpassed the single-junction limit, while the performance of N-I-P type PSTSCs is far below the theoretical value. Here, we developed a composite electron transport layer for N-I-P type monolithic PSTSCs with enhanced open-circuit voltage (VOC) and power conversion efficiency (PCE). Lithium chloride (LiCl) was added into the tin oxide (SnO2) precursor solution, which simultaneously passivated the defects and increased the electron injection driving force at the electron transfer layer (ETL)/perovskite interface. Eventually, we achieved monolithic PSTSCs with an efficiency of 25.42% and VOC of 1.92 V, which is the highest PCE and VOC in N-I-P type perovskite/Si tandem devices. This work on interface engineering for improving the PCE of monolithic PSTSCs may bring a new hot point about perovskite-based tandem devices.