Ternary Cd(Se,Te) alloy semiconductors: Synthesis, material characterization, and high-efficiency photoelectrochemical cells

High-quality Cd(Se,Te) in two compositions were synthesized using the modified Bridgman technique. The Se-rich crystals had the hexagonal structure while the Te-rich phase consisted of crystals with cubic packing. Their quality could be gauged from the high-electron mobility and their low resistivity which suited the purpose of their synthesis, i.e., for high-efficiency photoelectrochemical cells. Photoelectrochemical etching was employed, which resulted in a heavily pitted surface with the density of the etch pits exceeding 109 cm−2. Quantum efficiency of the semiconductor/aqueous polysulfide interface increased considerably after photoetching. Solar to electrical conversion efficiencies in excess of 12% were obtained. Photoluminescence spectrum was measured for the two crystals prior to and after photoetching. The emission maximum is near the calculated band gap. The decline in the luminescence intensity, after photoetching, is attributed to the corrugation of the surface and the reduced density of the donor state near the semiconductor surface, which increases the thickness of the space-charge layer (dead layer model).