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Effects of material properties of band‐gap‐graded Cu(In,Ga)Se 2 thin films on the onset of the quantum efficiency spectra of corresponding solar cells
Author(s) -
Thomas Sinju,
Bertram Tobias,
Kaufmann Christian,
Kodalle Tim,
Márquez Prieto José A.,
Hempel Hannes,
Choubrac Leo,
Witte Wolfram,
Hariskos Dimitrios,
Mainz Roland,
Carron Romain,
Keller Jan,
ReyesFigueroa Pablo,
Klenk Reiner,
AbouRas Daniel
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.3572
Subject(s) - quantum efficiency , band gap , materials science , spectral line , radiative transfer , crystallite , photoluminescence , solar cell , spontaneous emission , analytical chemistry (journal) , optoelectronics , condensed matter physics , optics , chemistry , physics , laser , chromatography , astronomy , metallurgy
Polycrystalline Cu(In,Ga)Se 2 (CIGSe) thin‐film solar cells exhibit gradual onset in their external quantum efficiency ( EQE ) spectra whose shape can be affected by various CIGSe material properties. Apart from influences on the charge‐carrier collection, a broadening of the EQE onset leads to enhanced radiative losses in open‐circuit voltage ( V oc ). In the present work, Gaussian broadening of parameters describing the EQE onset of thin‐film solar cells, represented by the standard deviation, total , was evaluated to study the impacts of the effective band‐gap energy, the electron diffusion length, and the Ga/In gradient in the CIGSe absorber. It is shown that total can be disentangled into contributions of these material properties, in addition to a residual component residual . Effectively, total depends only on a contribution related to the Ga/In gradient as well as on residual . The present work highlights the connection of this compositional gradient, the microstructure in the polycrystalline CIGSe absorber, and the luminescence emission with the residual component residual . It is demonstrated that a flat band‐gap with no compositional gradient in the bulk of the CIGSe absorber is essential to obtain the lowest total values and thus result in lower recombination losses and gains in V oc .