Electrical and impedance spectroscopy analysis of sol-gel derived spin coated Cu_2ZnSnS_4 solar cell

摘要

We carried out electrical and impedance studies on solution derived Al:ZnO/ZnO/CdS/Cu_2ZnSnS_4/ Mo/Glass multilayered solar cell structures to understand their impact on photovoltaic performance. The Cu_2ZnSnS_4 layer is synthesized on a molybdenum (Mo) coated soda lime glass substrate as an absorber and characterized intensively to optimize the absorber physical properties. The optimized Cu_2ZnSnS_4 is p-type with 5.8 × 10~(17)cm~(-3) hole carrier concentration. The depletion width of the junction is around 20.5 nm and the diffusion capacitance is ～35.5 nF for these devices. We observed relatively large minority carrier life time ～23 μs for these structures using open voltage decay analysis. The measured Cu_2ZnSnS_4/MoS_2 and Cu_2ZnSnS_4CdS interface resistances are 7.6 kΩ and 12.5kΩ, respectively. The spatial inhomogeneities are considered and the corresponding resistance is ～ 11.4 kΩ. The impedance measurements suggest that in conjunction with series resistance ～350 Ω, the interface and spatial inhomogeneity resistances also give a significant contribution to the photovoltaic performance.