Determination of lifetime and surface recombination velocity in solar cells

A detailed theoretical analysis was made of a new experimental practice for determining the minority carrier lifetime τ_n and the back surface recombination velocity $\text{S}{}_{\mathrm{<mtext>B</mtext>}}$ in silicon solar cells by the short circuit current decay method. The measurements were taken by monitoring both the current-voltage characteristics and a single transient of an operating cell at any level of injection when no power supply is required. The complete continuity differential equation for minority carrier transport including the generation rate of carriers is considered. A practicable analytical expression of the current response derived and the analysis includes both thick and thin base cells. Good precision and sensitivity are obtained for actual high quality solar cells and a lower precision appears for high values of both τ_n and $\text{S}{}_{\mathrm{<mtext>B</mtext>}}$ (τ_n greater than the extrinsic lifetime value as defined by the Shockley-Read-Hall recombination process, $\text{S}{}_{\mathrm{<mtext>B</mtext>}}$ greater than 10⁴ cm/s). Experimental results are presented to support the mathematical analysis.