Radiative Efficiency and Charge‐Carrier Lifetimes and Diffusion Length in Polycrystalline CdSeTe Heterostructures

CdTe-based photovoltaics is a rapidly developing energy technology with one of the lowest levelized costs of electricity. But nonradiative Shockley-Read-Hall (SRH) recombination limits the efficiency of CdTe solar cells. Partial mitigation of bulk and grain-boundary SRH recombination was achieved by alloying CdTe with Se, and CdSexTe1-x absorbers are used in high-efficiency solar cells. Recently, interface recombination was significantly reduced with alumina passivation, but other properties of Al2O3/CdSexTe1-x/Al2O3 heterostructures have not yet been investigated. Herein, further progress in understanding and developing polycrystalline heterostructures with x = 0.2 is reported. It is shown that external photoluminescence quantum yield is increased to 0.2%, quasi-Fermi-level splitting to 950 mV, minority carrier lifetimes to 750 ns, and mobility to 100 cm(2) Vs(-1). Such polycrystalline CdSexTe1-x electronic characteristics match or exceed CdTe single-crystal properties. The resulting charge-carrier diffusion length of approximate to 14 mu m is several times greater than the absorber thickness in test structures and in typical CdTe solar cells. Herein, with passivation and absorbers, polycrystalline CdSeTe solar cell open-circuit voltage is increased from the current 76% of the Shockley-Queisser limit to 82%, or close to 1 V is reported.