Study of Open-Circuit Voltage in CdTe/MgCdTe Double-Heterostructure Solar Cells with Different Hole Contacts

This paper reports a comparison study of open-circuit voltage (VOC) in three kinds of CdTe/MgCdTe doubleheterostructure solar cells featuring p-type a-Si:H, ZnTe:As or ZnTe:Cu as hole contact layers, respectively. Devices with p-type a-Si:H demonstrated a record V
_OC
of 1.1 V while the V
_OC
of the devices with p-type ZnTe:As and ZnTe:Cu drop below 0.9 V C-V measurements and time-resolved photoluminescence measurements reveal built-in voltages (V
_bi
) of 1.20 V, 1.23 V and 0.90 V, and minority carrier lifetime 300 ns, 52 ns and 170 ns for devices with different types of hole contacts, respectively. For the devices with a ZnTe:As layer, an increase in nonradiative recombination rate and a reduction in V
_OC
are observed due to the misfit dislocations at the ZnTe/MgCdTe interface. The low V
_OC
seen in the devices with a ZnTe: Cu layer is mainly limited by their low V
_bi
.