Abstract:
Electrolyte electroreflectance is used to show that the main effect of Br2/MeOH etching of CuInSe2 is to remove the pinning of the Fermi level, which is due to a monolayer of states located 0.17V positive to the potential of CuInSe2 the solution. The flatband potential of in polysulfide solution was found to be ?0.62V vs. the solution potential, while in polyiodide solution it is shifted to ?0.70V vs. the potential of that solution. This shift can explain some of the improvement in performance in polyiodide compared to polysulfide. The bandgap of CuInSe2 was found to be a direct transition at 1.01 eV with a three?dimensional critical point.