Tailored self-assembled monolayer molecules for perovskite/PERC tandem solar cells with efficiencies over 30%

The commercialization of perovskite/Si tandem solar cells requires low product costs, achievable through high efficiency and inexpensive components. Here, we report a highly efficient monolithic perovskite tandem device utilizing a commercial passivated emitter and rear cell (PERC), with the aid of a fluorine-substituted carbazole-based self-assembled monolayer (SAM). Modified SAM molecules enhanced charge transfer due to the larger dipole moments resulting from asymmetric charge distribution. The negative adsorption energy and well-ordered molecules alleviated residual stress in perovskite films and reduced trap density at the interfaces, leading to suppressed non-radiative recombination and improved open-circuit voltage of the perovskite top cell. As a result, the best single-junction perovskite cell exhibits a certified efficiency of 20.14%, with a good operational stability maintaining 90% of its initial efficiency after 1500 hours. The best perovskite/Si tandem cell, fabricated with cost-effective PERC bottom cells, exhibits a conversion efficiency of 30.05%, which is the highest among PERC-based perovskite tandem solar cells.