Photovoltaic properties of ZnSe/metal-free phthalocyanine heterojunctions deposited on substrates of InP single crystals

Heterojunctions of n-ZnSe/p-H2Pc have been fabricated by thermal evaporation technique of zinc selenide and metal-free phthalocyanine layers onto p-InP (100) single-crystal wafers. Rectifying properties have been obtained and capacitance-voltage behavior indicates an abrupt interface. The transverse current-voltage characteristics of H2Pc/InP, ZnSe/InP and ZnSe/H2Pc/InP junctions have been observed in the dark and under illumination. The ZnSe/H2Pc/InP junction exhibits a strong photovoltaic response with a power conversion efficiency of 1%. The photocarrier generated in H2Pc layer is separated by the steep incline of the potential near the H2Pc/ZnSe interface. Analysis of the dark J-V characteristics as a function of temperature indicates that the conduction mechanism in the forward direction has been explained by a tunneling process. The calculated activation energy of charge carriers is found to be 0.33 eV.