Losses due to polycrystallinity in thin-film solar cells

The highest efficiency thin-film polycrystalline CuIn_1−xGa_xSe₂ (CIGS) and CdTe solar cells are compared directly with crystalline Si and GaAs cells with similar respective bandgaps. The excess efficiency losses (6.3% for CIGS and 9.9% for CdTe) are quantitatively separated into eight categories. In each case, the impact of polycrystallinity is evaluated, and the differential losses are identified as being directly attributable to polycrystallinity or due to other causes. Approximately, two-thirds of the excess loss for polycrystalline cells is clearly due to polycrystallinity. Thus, strategies such as grain passivation to reduce the impact of polycrystallinity should be examined, but at the same time conventional approaches for incremental improvement should receive attention.