Optical, electrical and photovoltaic properties of thermally evaporated 3-amino-2-[(2-nitrophenyl)diazinyl]-3-(piperidin-1-yl)acrylonitrile thin films

Thin films with various thickness of 3-amino-2-[(2-nitrophenyl)diazinyl]-3-(piperidin-1-yl)acrylonitrile (ANPA) were produced by conventional thermal evaporation. The dependence of the optical, electrical, and photovoltaic properties on the film thickness was investigated. X-ray diffraction showed that the films have an amorphous structure. The optical properties were investigated in terms of transmittance and reflectance in the spectral range 200-2500 nm. Spectral distribution analysis of the absorption coefficient revealed that the films have an indirect allowed electronic interband transition. The optical bandgap decreased from 2.47 to 2.1 eV for an increase in film thickness from 105 to 265 nm. The direct current electrical conductivity of the films was measured for sandwich-structured samples as a function of the heating temperature and film thickness. The films exhibited semiconductor behavior and electrical conduction was attributed to hopping of charge carriers in localized states. ANPA films of differing thickness were deposited on p-type Si single-crystal substrates. The influence of film thickness on the electrical and photovoltaic parameters of Au/ANPA/p-Si/Al heterojunction solar cells was investigated.