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Near surface defects: Cause of deficit between internal and external open‐circuit voltage in solar cells
Author(s) -
Sood Mohit,
Urbaniak Aleksander,
Kameni Boumenou Christian,
Weiss Thomas Paul,
Elanzeery Hossam,
Babbe Finn,
Werner Florian,
Melchiorre Michele,
Siebentritt Susanne
Publication year - 2022
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.3483
Subject(s) - open circuit voltage , band gap , materials science , optoelectronics , solar cell , photoluminescence , voltage , condensed matter physics , electrical engineering , physics , engineering
Abstract Interface recombination in a complex multilayered thin‐film solar structure causes a disparity between the internal open‐circuit voltage ( V OC,in ), measured by photoluminescence, and the external open‐circuit voltage ( V OC,ex ), that is, a V OC deficit. Aspirations to reach higher V OC,ex values require a comprehensive knowledge of the connection between V OC deficit and interface recombination. Here, a near‐surface defect model is developed for copper indium di‐selenide solar cells grown under Cu‐excess conditions. These cell show the typical signatures of interface recombination: a strong disparity between V OC,in and V OC,ex , and extrapolation of the temperature dependent q · V OC,ex to a value below the bandgap energy. Yet, these cells do not suffer from reduced interface bandgap or from Fermi‐level pinning. The model presented is based on experimental analysis of admittance and deep‐level transient spectroscopy, which show the signature of an acceptor defect. Numerical simulations using the near‐surface defects model show the signatures of interface recombination without the need for a reduced interface bandgap or Fermi‐level pinning. These findings demonstrate that the V OC,in measurements alone can be inconclusive and might conceal the information on interface recombination pathways, establishing the need for complementary techniques like temperature dependent current–voltage measurements to identify the cause of interface recombination in the devices.