Diode Factor in Solar Cells with Metastable Defects and Back Contact Recombination. Issue 44 (22nd September 2022)

• Record Type: Journal Article
• Authors: Wang, Taowen; Ehre, Florian; Weiss, Thomas Paul; Veith‐Wolf, Boris; Titova, Valeriya; Valle, Nathalie; Melchiorre, Michele; Ramírez, Omar; Schmidt, Jan; Siebentritt, Susanne
• Is Part Of: Advanced energy materials. Volume 12:Issue 44(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-09-22
• Subjects: back contacts -- CIGSe -- optical diode factor -- photoluminescence; Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.202202076
• Languages: English
• ISSNs: 1614-6832

Abstract

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. Abstract : Optical diode factor, determined from illumination‐dependent photoluminescence (PL), is the lower limit of the diode factor. It is increased beyond 1 by metastable defects. Higher backside recombination and higher doping mitigate the higher diode factor, but only higher doping leads also to higher open circuit voltage.