Title :
Impact of Na on structural properties and interdiffusion of CuInSe/sub 2/ and CuGaSe/sub 2/ thin films
Author :
Rudmann, D. ; Kaelin, M. ; Haug, F.-J. ; Kurdesau, F. ; Zogg, H. ; Tiwari, A.N.
Author_Institution :
Lab. for Solid State Phys., Swiss Fed. Inst. of Technol., Zurich, Switzerland
Abstract :
We have grown CuInSe/sub 2/ (CIS) and CuGaSe/sub 2/ (CGS) thin films with the 3-stage process in the presence and absence of Na and observed a Na-induced decrease of grain size for CGS, but not for CIS. In addition, sodium was found to hinder the interdiffusion of In and Ga in Cu(In,Ga)Se/sub 2/ (ClGS) layers, which has consequences for the achievement of band-gap grading in high-efficiency absorbers. Two different mechanisms which can explain both Na effects are discussed. A post-deposition Na incorporation method was used to process solar cells with high efficiency (14.4%) at low substrate temperature (450/spl deg/C). The strong enhancement of device performance compared with Na- free cells is attributed to passivation of defects at grain boundaries. The result is promising for the development of flexible solar cells.
Keywords :
chemical interdiffusion; copper compounds; energy gap; gallium compounds; grain boundaries; grain size; indium compounds; passivation; semiconductor thin films; sodium; solar absorber-convertors; solar cells; ternary semiconductors; 14.4 percent; 3-stage process; 450 degC; NaCu(InGa)Se/sub 2/; NaCuGaSe/sub 2/; NaCuInSe/sub 2/; band-gap grading; flexible solar cell; grain boundaries; grain size; high efficiency absorber; interdiffusion; passivation; post-deposition Na incorporation method; structural properties; thin film;
Conference_Titel :
Photovoltaic Energy Conversion, 2003. Proceedings of 3rd World Conference on
Conference_Location :
Osaka, Japan
Print_ISBN :
4-9901816-0-3
