Clues from defect photochemistry

The efficiency of a solar cell is intimately related to the fate of photogenerated electron-hole pairs in the absorber layer. The interaction and capture of charge carriers through defects acting as recombination centres may significantly limit the solar cell's open-circuit voltage and thus depress its overall performance. The efficient charge generation and collection in devices based on lead-halide perovskites are, to a first approximation, related to the extremely long lifetimes of photogenerated carriers. These lifetimes depend on the intrinsic nature of the charge carriers -- particularly the electronic band structure and charge-lattice interactions -- and on the optoelectronic quality of the semiconductor (that is, the amount of traps/defects interacting with the carriers).