Simulation of heat generation from defects at different energy levels in CZTSSe thin film solar cells

• Published in: Optical and quantum electronics 2022-11, Vol.54 (11), Article 736
• Main Author: Hajjiah, Ali
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Computer Communication Networks; Conduction bands; Defects; Electrical Engineering; Energy; Energy levels; Heat generation; Lasers; Lasers and Photovoltaics Applications; Modules; Optical Devices; Optics; Photonics; Photovoltaic cells; Physics; Physics and Astronomy; Radiative recombination; Recent Advances of Advanced Functional Materials for Optics; Simulation; Simulation models; Solar cells; Thin films
• ISSN: 0306-8919; 1572-817X
• DOI: 10.1007/s11082-022-04069-w

Heat generation has been recognized as a detrimental factor to the performance stability of thin-film solar cells. A major part of this heat generation is due to recombination of defects located at near mid-gap level and interface. However, the other defects (acceptor/donor) located at different energy levels in the absorber layer of a solar cell will also contribute to recombination via shallow or deep defect levels and thus to heat generation in the cell. Nevertheless, there is no report in the literature on investigating the heat generation due to recombination into defects at shallow or deep levels in the cell. This simulation study focuses on the analysis of heat generation due to defects located at different energy levels in the bulk of a Cu 2 ZnSn 4 SxSe 4-x  (CZTSSe) based thin-film solar cells. A strong simulation model has been developed by coupling the optical, electrical, and heat modules in the COMSOL simulation package. Different defect levels with shallow or deep energy (known by experimental data reported in the literature) have been inserted in the semiconductor module and the heat generation due to non-radiative recombination to these levels has been calculated, separately. To calculate the recombination at these deep/shallow levels, an additional recombination component has been added in COMSOL, in addition to conventional Shockley–Read–Hall recombination (for mid-gap defects). It is concluded that the deep energy levels close to the mid-gap level generate (5%) more heat compared to shallow defects located at energy levels close to valence or conduction bands. Fill factor drops 11% due to defect closer to mid-gap which represents the cell instability due to higher heat generated due to this defect level.