Comparative photovoltaics studies of prominent PV materials, organometal halide perovskite, CdTe, and GaAs with direct comparison of carrier recombination through power dependent photoluminescence*

Comparative Photovoltaics refers to the study of material properties of different PV materials by making direct and meaningful comparison to reveal their relative strength and weakness. Although the hybrid perovskite based solar cell has reached up to 23.3% energy conversion efficiency, it remains unclear what the enabling factors are for the impressive performance, in particular how it differs from the better-known PV materials CdTe and GaAs. Power dependent PL measurements show that perovskite samples tend to have stronger PL than the inorganic counterparts in the very low excitation density region (e.g., 0.1 – 1 sun), indicating that Shockley-Read-Hall (SRH) recombination is relatively less effective in the perovskite. PL lineshape analysis suggests that carriers in the perovskite are not in thermal equilibrium due to structural disordering, which in turn suppresses the nonradiative recombination. Both relatively low effective point defect density and moderate crystalline disordering in the perovskite contribute to the low nonradiative recombination loss, thus, high cell efficiency.