Comparison of the properties of porous silicon films with different back contacts (Ag, Al) for possible photovoltaic applications

Abstract

In this work, porous silicon (PS) films were prepared by anodization on polished substrates of (1 0 0) Si for a fixed current density ( I d)∼20 mA cm −2 and for a fixed anodization time of 30 min using different screen-printed (SP) back contacts, namely Ag and Al. The properties of PS formed using Ag as the back contact were found to be superior compared to the corresponding film using Al as the back contact. The PS formed with Ag-back contact exhibits higher porosity, negligible photoluminescence (PL) decay, better adherence to the substrate and smooth surface morphology compared to that formed with Al as the back contact for the same current density and time of anodization. Fourier transform infrared (FTIR) studies indicated significant presence of Si–O related features at ∼1050–1150 cm −1 for PS films formed with Al as back contact, which could be responsible for traps and interface (PS–Si) defect densities as compared to corresponding PS films with Ag as the back contact. Measurements of capacitance–voltage ( C– V) and current–voltage ( I– V) were used for the investigation of the electrical properties of PS films with different back contacts. The frequency-dependent C– V characteristics were analysed to understand the effects of interface states and traps on the properties of PS films. The results have been analysed in terms of eutectic temperature and back surface field (BSF) across the metal–silicon interface.