Developing metal-halide perovskites with optimal band gaps, slow recombination and high stability for tandem solar cells

We have made perovskite on silicon tandem solar cells with efficiency greater than 25 %. We have also made all-perovskite tandems using an ABX3 perovskite composition containing a mixture of tin and lead on the B site that have greater than 20% efficiency. We will show how the composition of the perovskite can be used to adjust the bandgap by controlling both the lattice parameter and octahedral tilting. We have measured the photovoltaic energy conversion efficiency and photoluminescence lifetime for a wide variety of perovskite compositions and observed interesting trends. We will present our progress in understanding why light -induced phase separation occurs in compounds with large amounts of bromine.