Premium
Surface preparation for 10% efficient CZTSe solar cells
Author(s) -
Grenet Louis,
Emieux Fabrice,
Choubrac Léo,
Márquez José A.,
De Vito Eric,
Roux Frédéric,
Unold Thomas
Publication year - 2021
Publication title -
progress in photovoltaics: research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.286
H-Index - 131
eISSN - 1099-159X
pISSN - 1062-7995
DOI - 10.1002/pip.3356
Subject(s) - passivation , open circuit voltage , annealing (glass) , kesterite , optoelectronics , carrier lifetime , materials science , photoluminescence , chemical bath deposition , voltage , energy conversion efficiency , isotropic etching , solar cell , analytical chemistry (journal) , chemistry , etching (microfabrication) , nanotechnology , electrical engineering , band gap , czts , silicon , composite material , layer (electronics) , engineering , chromatography
Kesterite‐based solar cells suffer from a large open‐circuit voltage deficit, which largely arises from carrier recombination at the buffer interface. In this study, we compare two strategies to passivate the absorber surface in order to fabricate devices with power conversion efficiency higher than 10% and an open‐circuit voltage deficit as low as 306 mV. These two strategies consist of annealing in air or performing a chemical etching of the absorbers before buffer deposition. They lead similarly to a significant reduction of the interface recombination but as well to a shortening of the minority carrier diffusion length from 1 μm to less than 500 nm. This latter effect limits the short‐circuit current and fill factor of the devices but is largely compensated by the open‐circuit voltage gain of more than 100 mV. For the absorber air annealing, which is the simplest solution to implement, absolute photoluminescence measurements reveal that the voltage gain is directly linked to a drop in the nonradiative losses in the absorber and to a small reduction of the band tailing. It is demonstrated that the removal of detrimental secondary phases at the surface of the absorber due to oxidation at elevated temperature and etching in the basic CdS solution is responsible for these improved opto‐electronic properties. On the contrary, the apparent Cu‐depletion observed after air annealing is totally recovered after the chemical bath and cannot be responsible for the improved performances.