Diode Factor in Solar Cells with Metastable Defects and Back Contact Recombination

authored by: Taowen Wang, Florian Ehre, Thomas Paul Weiss, Boris Veith-Wolf, Valeriya Titova, Nathalie Valle, Michele Melchiorre, Omar Ramírez, Jan Schmidt, Susanne Siebentritt
Abstract: To achieve a high fill factor, a small diode factor close to 1 is essential. The optical diode factor determined by photoluminescence is the diode factor from the neutral zone of the solar cell and thus a lower bound for the diode factor. Due to metastable defects transitions, the optical diode factor is higher than 1 even at low excitation. Here, the influence of the backside recombination and the doping level on the optical diode factor are studied. First, photoluminescence and solar cell capacitance simulator (SCAPS) simulations are used to determine the back surface recombination velocity of Cu(In, Ga)Se₂ with various back contacts and different doping levels. Then, experimental results and simulations show that both back surface recombination and high doping density reduce the optical diode factor. The back surface recombination reduces the optical diode factor with undesirable extra nonradiative recombination. The smaller value achieved by higher doping can increase quasi-Fermi level splitting at the same time. The simulations show that the back surface recombination reduces the optical diode factor due to an illumination-dependent recombination rate. In addition, a higher majority carrier doping reduces the influence of majority carrier gain from metastable defect transitions, thus reducing the optical diode factor.
Organisation(s): Institute of Solid State Physics
External Organisation(s): University of Luxembourg
Institute for Solar Energy Research (ISFH)
Centre de Recherche Public – Gabriel Lippmann Informatics, Systems and Collaboration (ISC)
Type: Article
Journal: Advanced energy materials
Volume: 12
ISSN: 1614-6832
Publication date: 24.11.2022
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Renewable Energy, Sustainability and the Environment, General Materials Science
Sustainable Development Goals: SDG 7 - Affordable and Clean Energy
Electronic version(s): https://doi.org/10.1002/aenm.202202076 (Access: Open)