Charge Carrier Lifetimes in Cr-Fe-Al-O Thin Films.

The effect of compositional variation on charge carrier lifetimes of Cr1 Fe0.84 Al0.16 O3 , a promising material for solar water splitting recently identified using combinatorial materials science, is explored using ultrafast time-resolved optical reflectance. The transient signal can be described by a biexponential decay, where the shorter time constant varies over 1 order of magnitude with changing Cr content while the longer one stays constant. Intrinsic performance limitations such as a low charge carrier mobility on the order of 10-3 cm2 /(Vs) are identified. Charge carrier lifetime and mobility are discussed as screening criteria for solar water splitting materials.