¹V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine,
41, prospect Nauky, 03680 Kyiv, Ukraine
²V.I. Vernadsky Institute of General and Inorganic Chemistry, NAS of Ukraine,
32/34, prospect Palladina, 03142 Kyiv, Ukraine
³Ontario Tech University, 2000 Simcoe St. N., Oshawa, ON, L1G 0C5, Canada
*Corresponding author e-mail: vkostylyov@ukr.net

Abstract. The properties of the synthesized films of organic-inorganic perovskites CH3NH3PbI3 obtained at various ratios of starting reagents (PbI2 and CH3NH3I) have been studied. As a solvent, we used chemically pure dried dimethylformamide (DMF). Organic-inorganic perovskites are promising for photovoltaic applications. It has been shown that regardless of the ratio of the starting reagents, single-phase perovskites are formed, at the same time the microstructure of the films changes significantly. It has been reported photoelectric and optical properties of synthesized films, namely: experimental and theoretical spectral dependences of the low-signal surface photovoltage and transmission. The band gap and the Urbach parameter dependence on the ratio of precursors were determined. It has been found that the materials’ band gap depends on the ratio of precursors and equals to 1.59, 1.62 and 1.57 eV, while the characteristic Urbach energy equals to 18, 19 and 22 meV for the PbI2:CH3NH3I films with PbI2 ratio of 1:1, 1:2 and 1:3, respectively. It has been ascertained that the spectral dependences of the low-signal surface photovoltage are much more sensitive to the material microstructure and its electronic structure close to the absorption edge, while the optical transmission spectra are not so sensitive. The limiting value of the short-circuit current density for the films with different PbI2 and CH3NH3I ratios has been determined.

Keywords:perovskites, surface photovoltage spectroscopy, optical properties.

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