Importance of charge defects in a-Si:H materials and solar cell structures

Detailed results and their analysis are presented for establishing the types and densities of gap states in a-Si:H, deposited from silane diluted with hydrogen, in the annealed and the degraded stabilized states. For /spl sim/1 /spl mu/m thick films the dependence of both the electron mobility-lifetime products (/spl mu//spl tau/) and subgap absorption measured with the dual beam photoconductivity (DBP) method over wide generation rates is self consistently fitted using an improved subgap absorption model (SAM). The self-consistent analysis of all the results could be carried out only by including donor-like D/sup +/, D/sup o/ and acceptor-like D/sup -/ defect states. "Operational" parameters of these states were derived for a three-gaussian distribution using AMPS with virtually identical gap state parameters. Excellent fits were then obtained for the far forward I-V characteristics of corresponding Schottky barrier cell structures in both the annealed and stabilised degraded states after changing by more than three to four orders of magnitude.