Optical and electrical characterizations of highly efficient CdTe thin film solar cells

Abstract The effect of CdCl2 treatment and the heat treatment for Cu diffusion were investigated in the CdTe thin film solar cells prepared by close-spaced sublimation (CSS) method. In the photoluminescence (PL) spectra of the CdCl2-treated CdTe layer, 1.42 eV band related to VCd–Cl defect complexes appeared. Capacitance–voltage (C–V) measurements revealed that the acceptor concentration was maximized at the optimum CdCl2 treatment temperature. Furthermore, a neutral-acceptor bound exciton line due to Cu acceptors was observed in the PL of the CdTe layer by the heat treatment for Cu diffusion. C–V characteristics and depth profile of PL spectrum implied that the heat treatment for Cu diffusion facilitated the formation of low resistance contacts to CdTe through formation of a heavily doped region in the CdTe near the back electrode, but Cu atoms did not act as effective acceptors in the CdTe layer except the region near the back electrode.