MODULATING CH3NH3PbI3 PEROVSKITE CRYSTALLIZATION BEHAVIOR THROUGH PRECURSOR CONCENTRATION

Perovskite-based photovoltaic devices have recently achieved impressively high efficiencies beyond 15% and gained great interest. We show here the formation of perovskite cluster overlayer structures which consist of individual perovskite grains on top of mesoporous TiO2 films, coexisting with the randomly distributed nanocrystals within the films. Perovskite solution concentration was found to play an important role in modulating the perovskite crystallization and cluster overlayer formation process. Absorbance increase in visible wavelength range and shift of photoluminescence (PL) responses of perovskite films due to the effect of precursor concentration change were observed and investigated in detail. The crystallographic analysis of the CH3NH3PbI3 films shows a gradual decrease of the perovskite lattice parameters and shrinkage of unit volume as precursor solution concentration increases, which is correlated to the changes of optical properties. Finally, perovskite-based solar cell device performance was enhanced at higher precursor concentration. Despite rapid increase of efficiency in solid-state perovskite solar cells, there has been limited exploration into the morphological and crystallographic characteristics of this kind of device. Here we show how the concentration of perovskite precursor plays a crucial role in CH3NH3PbI3-based devices. The optical analysis reveals an absorbance increase and a shift of photoluminescence responses towards lower energies with increasing concentratio. Additionally, the crystallographic study shows a gradual decrease of the perovskite lattice parameters. These differences determine the photovoltaic performance of the solar cells.

KUNWU FU et al

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