Potential fluctuations in Cu2ZnSnSe4 solar cells studied by temperature dependence of quantum efficiency curves

A new method to study spatial potential fluctuations in compensated absorber materials used in solar cells is introduced. The method is based on the analysis of the temperature dependence of quantum efficiency curves in solar cells. As an example Cu2ZnSnSe4 monograin solar cell is studied at temperatures T=10–300 K. It is shown that this absorber material has spatial potential fluctuations with an average energetic depth of 25 meV. The room temperature bandgap energy of Cu2ZnSnSe4 is found to be Eg=1.017 eV.