Two-dimensional perovskite solar cells with high luminescence and ultra-low open-circuit voltage deficit

High luminescence efficiency of the halide perovskite absorber layer in perovskite solar cells (PVSCs) will reduce the open-circuit voltage (V-oc) loss and further increase the cell efficiency. Still, while quasi-2D-structure perovskite films exhibit high emissivity in light-emitting devices, quasi-2D PVSCs show severe V-oc loss associated with non-radiative recombination. Here we demonstrate how the use of highly luminescent PEA(0.2)BA(1.8)MA(3)Pb(4)I(13) in quasi-2D PVSCs allows, via Cl- passivation and heat-light post-co-treatment, a champion external electroluminescence quantum efficiency around 2.3% and a record low V-oc deficit of 0.36 eV. To our knowledge, this is the lowest V-oc loss for quasi-2D PVSCs and among the lowest for any type of PVSCs. As a result, high performance quasi-2D PVSCs are obtained, with a V-oc up to 1.29 V and 15.81% efficiency, showing excellent stability, and retain 98% of the original efficiency after heating at 85 degrees C for 1590 h. This work paves the way toward highly luminescent and efficient quasi-2D PVSCs.