ANALYSIS OF INTERNAL QUANTUM EFFICIENCY AND A NEW GRAPHICAL EVALUATION SCHEME

The analysis of internal quantum efficiency data is extended by a new graphical evaluation scheme. On the one hand, our method allows one to estimate the minority carrier diffusion length L and the back surface recombination velocity S. On the other hand the limitations of the internal quantum efficiency method are studied. A mathematical treatment of the equations describing internal quantum efficiency demonstrates that already a single measurement of either the effective diffusion length L(eff) measured in the near infrared, or the collection efficiency eta(c) measured in the near bandgap wavelength range, yields limits for L and S. More precise values can be obtained in specific cases, if the analysis of L(eff) and eta(c) are combined. In those cases, information about the accuracy of L and S is obtained. We present a graphical solution for the evaluation and illustrate our method using quantum efficiency data from both thick and thin silicon solar cells.