Investigation of the open-circuit voltage in wide-bandgap InGaP-host InP quantum dot intermediate-band solar cells

Abstract

To analyze the open-circuit voltage (Voc) in intermediate-band solar cells, we investigated the current–voltage characteristics in wide-bandgap InGaP-based InP quantum dot (QD) solar cells. From the temperature dependence of the current–voltage curves, we show that the Voc in InP QD solar cells increases with decreasing temperature. We use a simple diode model to extract Voc at the zero-temperature limit, V0, and the temperature coefficient C of the solar cells. Our results show that, while the C of InP QD solar cells is slightly larger than that of the reference InGaP solar cells, V0 significantly decreases and coincides with the bandgap energy of the InP QDs rather than that of the InGaP host. This V0 indicates that the Voc reduction in the InP QD solar cells is primarily caused by the breaking of the Fermi energy separation between the QDs and the host semiconductor in intermediate-band solar cells, rather than by enhanced carrier recombination.