Modeling of the impact of Se-vacancies on the electrical properties of Cu(In,Ga)Se2 films and junctions

• Published in: Thin solid films Vol. 535; pp. 371 - 375
• Main Authors: Maciaszek, M., Zabierowski, P., Decock, K.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15.05.2013; Elsevier
• Subjects: Applied sciences; Capacitance voltage profiling; CIGS; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Defects and impurities: doping, implantation, distribution, concentration, etc; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport phenomena in thin films and low-dimensional structures; Energy; Exact sciences and technology; Metastable defects; Natural energy; Photovoltaic conversion; Physics; Se vacancy; Solar cells. Photoelectrochemical cells; Solar energy; Surface and interface electron states; Surface states, band structure, electron density of states; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; CIGS; Metastable defects; Se vacancy; Capacitance voltage profiling; Gallium; Indium selenides; Metastable states; Doping; Space charge; CV characteristic; Thin films; Shallow level; Modelling; Copper; Depth profiles; Electrical characteristic; Solar cells; Defect density; Vacancies; Defect level; Electrical properties; Theoretical study; Free carrier; Copper selenides; Electronic structure; Fermi level; Carrier density; Gallium selenides; Concentration distribution
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2013.01.035

In this contribution we aim at a better understanding the influence of metastable VSe defects on electrical characteristics of Cu(In,Ga)Se2-based solar cells. In order to achieve this goal we calculate the distribution of VSe charge states by solving numerically the equations involving transition rates between the metastable donor and acceptor configuration. By varying systematically the set of three parameters in a broad range (net shallow acceptor doping level, VSe defect density and temperature) we analyze quantitatively in which conditions and how the metastable defects influence/control the Fermi level position and hence the free carrier concentration. Using these results, we calculate time constants for conversion processes between donor and acceptor configurations. In the second part of the paper we model the influence of VSe-related defects on capacitance–voltage (CV) space charge profiles in different metastable states (reverse bias and light soaking). We propose a method allowing the evaluation of the lower bound for the metastable VSe defect concentration from CV profiles. ► Influence of VSe-related defects on hole concentration in Cu(In,Ga)Se2 established ► Qantitative analysis of space charge profiles in the presence of metastable defects ► A method for evaluation of VSe-related defect concentrations proposed.