Incorporation of an electron reflector is a proposed strategy to improve the open-circuit voltage of CdTe thin-film solar cells. An electron reflector is basically a conduction-band barrier at the back surface, which can reduce the recombination resulting from the electron flow to the back surface. It should be particularly beneficial for cells with thicknesses below two microns when the CdTe absorber layer is fully depleted at its typical carrier density, because back-surface recombination is a primary limitation to the performance of fully depleted cells. Cells with thickness below two microns can also benefit from optical reflection at the back interface.
One-dimension numerical simulation is used to investigate the electron reflector strategy and optical back reflection for thin CdTe cells. Theoretically, about a 200-mV increase in voltage and 3% in efficiency are achievable for a thin CdTe solar cell with 2×1014-cm-3 hole density, 1-ns lifetime, and a 0.2-eV electron reflector barrier. Furthermore, with the electron reflector, good CdTe cell performance at thicknesses as thin as 0.4 μm should be possible.