Optoelectronic properties of GaP:Ti photovoltaic devices

Abstract

Supersaturated GaP is of interest for the photovoltaic field since optical transitions at energies below the bandgap (2.26 eV) could enhance the overall device efficiency up to theoretically 60%. We have previously demonstrated that Ti supersaturated GaP can be obtained by means of ion implantation and pulsed-laser melting with high structural quality and measured its below-bandgap photoconductivity. In this work we report the first results of a GaP:Ti based photovoltaic device. We have fabricated and measured photovoltaic devices with a GaP:Ti absorber layer showing enhanced external quantum efficiency at wavelengths above 550 nm. Also, we have measured the absorption coefficient (around 104 cm−1) and refractive index of this absorber layer. Finally, current-voltage curves in darkness were measured and analyzed using a two-diodes model, showing improvable characteristics. Ideas to enhance the properties of the devices are suggested.