Abou-Ras, D.; Schmidt, S.S.; Schäfer, N.; Kavalakkatt, J.; Rissom, T.; Unold, T.; Mainz, R.; Weber, A.; Kirchartz, T.; Simsek, E.; van Aken, P.A.; Ramasse, Q.M.; Kleebe, H.-J.; Azulay, D.; Balberg, I.; Millo, O.; Cojocaru-Mirédin, O.; Barragan-Yani, D.; Albe, K.; Haarstrich, J.; Ronning, C.: Compositional and electrical properties of line and planar defects in Cu(In,Ga)Se2 thin films for solar cells – a review. Physica Status Solidi - Rapid Research Letters 10 (2016), p. 363-375
The present review gives an overview of the various reports on properties of line and planar defects in Cu(In,Ga)(S,Se)2 thin films for high-efficiency solar cells. We report results from various analysis techniques applied to characterize these defects at different length scales, which allow for drawing a consistent picture on structural and electronic defect proper- ties. A key finding is atomic reconstruction detected at line and planar defects, which may be one mechanism to reduce excess charge densities and to relax deep-defect states from midgap to shallow energy levels. On the other hand, nonra- diative Shockley–Read–Hall recombination is still enhanced with respect to defect-free grain interiors, which is correlated with substantial reduction of luminescence intensities. Com- parison of the microscopic electrical properties of planar defects in Cu(In,Ga)(S,Se)2 thin films with two-dimensional device simulations suggest that these defects are one origin of the reduced open-circuit voltage of the photovoltaic devices.