Despite many recent research efforts, the influence of grain boundaries on device properties of CuIn1−xGaxSe2 solar cells was still not fully understood Here, a microscopic approach was used to characterize grain boundaries in polycrystalline CuIn1−xGaxSe2 films with x = 0.33. On samples from the same deposition process methods were applied which furnished complementary information, i.e., electron back-scattering diffraction, electron-beam induced current measurements, conductive atomic force microscopy, variable-temperature Kelvin probe force microscopy and scanning capacitance microscopy. By combining electron-beam induced current measurements with electron back-scattering diffraction, a decrease in charge-carrier collection was found for non-∑3 grain boundaries, while ∑3 grain boundaries exhibited no variation with respect to grain interiors. In contrast, a higher conductance of grain boundaries compared to grain interiors was found by conductive atomic force microscopy at low bias and under illumination. By Kelvin probe force microscopy, the band bending at grain boundaries was directly measured; finding a range from -80 up to 115mV. Depletion and even inversion at grain boundaries was confirmed by scanning capacitance microscopy. The apparent differences between the results obtained by various microscopic techniques were considered.

Nanometer-Scale Electronic and Microstructural Properties of Grain Boundaries in Cu(In,Ga)Se2. S.Sadewasser, D.Abou-Ras, D.Azulay, R.Baier, I.Balberg, D.Cahen, S.Cohen, K.Gartsman, K.Ganesan, J.Kavalakkatt, W.Li, O.Millo, T.Rissom, Y.Rosenwaks, H.W.Schock, A.Schwarzman, T.Unold: Thin Solid Films, 2011, 519[21], 7341-6