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).