Development of ZnTe1−xOx intermediate band solar cells

We describe the fabrication of ZnTe_1-xO_x intermediate band solar cell (IBSC) using the combination of oxygen ion implantation and pulsed laser melting. Also, we report the first demonstration of homojunction ZnTe solar cells in which n-ZnTe layer is fabricated by thermal diffusion of Al into p-ZnTe. The preliminary results of the ZnTe_1-xO_x IBSC are compared with the ZnTe cell. The homojunction ZnTe solar cells exhibited photovoltaic activity with an open circuit voltage of approximately 0.9 V and a maximum short circuit current (J_SC) of 1.75 mA/cm². J_SC was found to depend strongly on the location of pn-junction, with shallower pn-junction depth, corresponding to higher J_SC. Photo-modulated reflectance spectra of ZnTe_1-xO_x, show two optical transitions from the valence band to the conduction subband E⁺ (~2.5 eV) and from the valence band to the intermediate band E^- (~1.7 eV). The external quantum efficiency of ZnTe_1-xO_x solar cell clearly shows PV responses due to the transition from valence band to the two conduction subbands (E^- and E⁺) demonstrating the photovoltaic action through the intermediate band in this highly mismatched alloy.