Determination of minority carrier diffusion length of sprayed-Cu₂ZnSnS₄ thin films

Despite Cu₂ZnSnS₄(CZTS) is a potential candidate for solar cell applications, so far, low efficiency values have been reported. In particular, for spray-deposited CZTS, efficiencies lower than 2% are commonly achieved. It is well known that one of the most important parameters governing solar cell performance is minority carrier diffusion length (L_n). In this work, CZTS thin film solar cells with different compositional ratios are fabricated in order to study its impact on L_n values. The L_n parameter is calculated for sprayed-CZTS layers using external quantum efficiency measurements in conjunction with optical absorption coefficient versus wavelength measurements - for the first time. Values in the range of 0.11-0.17 μm are obtained emphasizing the need for improving sprayed-CZTS crystalline quality.