A simulation study of the effect of the diverse valence-band offset and the electronic activity at the grain boundaries on the performance of polycrystalline Cu(In,Ga)Se2 solar cells

• Published in: Thin solid films Vol. 519; no. 21; pp. 7497 - 7502
• Main Authors: NERAT, Marko, SMOLE, Franc, TOPIC, Marko
• Format: Conference Proceeding Journal Article
• Language: English
• Published: Amsterdam Elsevier 31.08.2011
• Subjects: Applied sciences; BOUNDARIES; COMPUTER SIMULATION; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; COPPER INDIUM SELENIDE; Crystal defects; DEFECTS; Defects and impurities: doping, implantation, distribution, concentration, etc; DENSITY; ELECTRONIC PRODUCTS; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronics; Energy; Exact sciences and technology; GRAIN BOUNDARIES; LATTICE DEFECTS; Natural energy; Offsets; Photovoltaic cells; Photovoltaic conversion; Physics; Simulation; SOLAR CELLS; Solar cells. Photoelectrochemical cells; Solar energy; Structure and morphology; thickness; 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; VALENCE; Solar cells; Grain boundaries; Defect density; Valence bands; Density of states; Crystal defects; Gallium; Indium selenides; Digital simulation; Space charge; Polycrystals; Diamond-like carbon; Copper selenides; Electronic structure; Numerical simulation; Band offset; Copper; Substrate/superstrate configuration; Gallium selenides; CIGS solar cell
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2010.12.100

The paper presents a two-dimensional simulation study of a polycrystalline Cu(In,Ga)Se2 (CIGS) solar cell with various shapes of grains inside the CIGS absorber layer. The grain boundaries (GBs) with a diverse valence-band offset (VBO) and the density of defect states (NtA) are considered so as to evaluate their effects on the performance of the CIGS cell. The numerical simulations show that a CIGS cell with column-like grains can achieve a high conversion efficiency ( eta ), while the eta of a CIGS cell with diamond-like grains is low if the VBO at the GBs exceeds 0.4 eV. The VBO at which the eta of the CIGS cell with diamond-like grains peaks is found at 0.200.27 eV. A favorable VBO mainly depends on the shape of the grains, but it also depends on the NtA. The simulations of the CIGS cells in the substrate and superstrate configurations showed that their performances change if the VBO is varied. This result also implies that the configuration of the CIGS cell is important and the substrate configuration with larger grains in the space-charge region has a considerable advantage if the VBO ranges from 0 eV to 0.2 eV.