Bulk and metastable defects in CuIn1−xGaxSe2 thin films using drive-level capacitance profiling

The drive-level capacitance profiling technique has been applied to ${\mathrm{ZnO/CdS/CuIn}}_{\text{1−x}}{\mathrm{Ga}}_x{\mathrm{Se}}_2/\mathrm{Mo}$ solar cell devices, in order to study properties of defects in the ${\mathrm{CuIn}}_{\text{1−x}}{\mathrm{Ga}}_x{\mathrm{Se}}_2$ film. Properties studied include the spatial uniformity, bulk defect response, carrier density, and light-induced metastable effects. These results indicate that previous estimates of carrier densities, from $\mathrm{C–V}$ profiling, may be significantly overestimated. In addition, a defect response previously thought to be located at the interface is observed to exist throughout the bulk material. Finally, an infrared light-soaking treatment is demonstrated to induce metastable changes in the bulk ${\mathrm{CuIn}}_{\text{1−x}}{\mathrm{Ga}}_x{\mathrm{Se}}_2$ film. Hence, the drive-level capacitance profiling technique provides valuable insights into these films. Herein, the technique itself is fully explained, compared to other junction capacitance methods, and its utility is demonstrated using numerical simulation.