Hole-selective Transparent In Situ Passivation Contacts for Efficient and Stable n-i-p Graded Perovskite/Silicon Tandem Solar Cells.

The optically deficient and intrinsically unstable hole transport layer (HTL) is the Achilles' heel of n-i-p perovskite/silicon tandems. Here, a minimalist transparent hole-selective contact is developed without additional HTL by simply integrating cross-linkable p-type small molecules into antisolvent. This strategy not only improves the perovskite crystallinity, shields the perovskite from external stressors, and suppresses interfacial mass exchange, but also provides efficient defect passivation and favorable band alignment via the formation of graded heterojunction. Consequently, the corresponding 1.65 eV perovskite solar cell achieves a stabilized efficiency of 19.6%, alongside significantly improved thermal, ultraviolet, and operation stabilities. Furthermore, leveraging its outstanding transparency, a bifacial single-junction device is showcased achieving a record bifaciality of 101.4%, and a monolithic perovskite/silicon tandem boasting a certified efficiency of 29.2% for 1.04 cm2, which represents the highest certified efficiency achieved for n-i-p perovskite/silicon tandems. The demonstration of efficient and stable minimalist hole-selective contacts encourages the tandem community to reevaluate the n-i-p structure, with the goal of harnessing the high open-circuit voltage of single-junction n-i-p PSCs.