Editors' Suggestion
Open Access
Access by Xinjiang University

Metastable Defects Decrease the Fill Factor of Solar Cells

Thomas Paul Weiss ¹, Omar Ramírez¹, Stefan Paetel ², Wolfram Witte ², Jiro Nishinaga³, Thomas Feurer ⁴, and Susanne Siebentritt ^1,*

¹Department of Physics and Materials Science, University of Luxembourg, 41, rue du Brill, L-4422 Belvaux, Luxembourg
²Zentrum für Sonnenenergie-und Wasserstoff-Forschung Baden-Württemberg (ZSW), Meitnerstraße 1, 70563 Stuttgart, Germany
³Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Japan
⁴Laboratory for Thin Films and Photovoltaics, Empa - Swiss Federal Laboratories for Materials Science and Technology, Überlandstraße 129, 8600 Dübendorf, Switzerland

^*susanne.siebentritt@uni.lu

PDF

Phys. Rev. Applied 19, 024052 – Published 17 February, 2023

DOI: https://doi.org/10.1103/PhysRevApplied.19.024052

Abstract

$Cu (In, Ga) {Se}_{2}$ -based solar cells exceed power conversion efficiencies of 23%. However, the fill factor of these solar cells, with best values around 80%, is relatively low ( $Si$ reaches 84.9%) mostly due to diode factors greater than 1. Recently, we proposed metastable defects, a general feature of the $Cu (In, Ga) {Se}_{2}$ alloy, to be the origin of the increased diode factor even in low injection. Here, we measure the diode factor of the bare absorber layers using excitation-dependent photoluminescence. The increased diode factor above 1 can be well described by the model of metastable defects, as well as a slight excitation dependence within the experimentally accessible range of excitation intensities. We discuss how the excitation dependence of the diode factor depends on the parameters of the metastable defects. Within the same model, we can additionally describe the experimental diode factors of n- and p-type epitaxial $Cu (In, Ga) {Se}_{2}$ films. We find that the diode factors measured optically by photoluminescence impose a lower limit for the diode factor measured electrically on a finished solar cell. Interestingly, the lowest diode factor (optical and electrical) and consequently highest fill factor of 81.0% is obtained by $Ag$ alloying, i.e., an $(Ag, Cu) (In, Ga) {Se}_{2}$ absorber. This finding hints to a pathway to increase fill factors and thus efficiencies for $Cu (In, Ga) {Se}_{2}$ -based solar cells.

Physics Subject Headings (PhySH)

Collections

This article appears in the following collection:

Photovoltaic Energy Conversion

Physical Review Applied is pleased to present a Collection on Photovoltaic Energy Conversion, in recognition of the imminent need to harness solar energy, and the key role that Applied Physics plays in that endeavor. Contributions to this collection will be published throughout 2021 and into 2022. The invited articles, plus an editorial by Guest Editors Shanhui Fan and Zetian Mi, are linked below.

Article Text

References (61)

M. Nakamura, K. Yamaguchi, Y. Kimoto, Y. Yasaki, T. Kato, and H. Sugimoto, Cd-free $Cu (In, Ga) (Se, S) 2$ thin-film solar cell with record efficiency of 23.35%, IEEE J. Photovoltaics 9, 1863 (2019).
S. Siebentritt, et al., Heavy alkali treatment of $Cu (In, Ga) {Se}_{2}$ solar cells: Surface versus bulk effects, Adv. Energy Mater. 10, 1903752 (2020).
M. Krause, A. Nikolaeva, M. Maiberg, P. Jackson, D. Hariskos, W. Witte, J. A. Márquez, S. Levcenko, T. Unold, R. Scheer, and D. Abou-Ras, Microscopic origins of performance losses in highly efficient $Cu (In, Ga) {Se}_{2}$ thin-film solar cells, Nat. Commun. 11, 4189 (2020).
M. A. Green, E. D. Dunlop, J. Hohl-Ebinger, M. Yoshita, N. Kopidakis, and X. Hao, Solar cell efficiency tables (Version 58), Prog. Photovoltaics 29, 657 (2021).
K. Yoshikawa, H. Kawasaki, W. Yoshida, T. Irie, K. Konishi, K. Nakano, T. Uto, D. Adachi, M. Kanematsu, H. Uzu, and K. Yamamoto, Silicon heterojunction solar cell with interdigitated back contacts for a photoconversion efficiency over 26%, Nat. Energy 2, 17032 (2017).
P. Jackson, R. Wuerz, D. Hariskos, E. Lotter, W. Witte, and M. Powalla, Effects of heavy alkali elements in $Cu (In, Ga) {Se}_{2}$ solar cells with efficiencies up to 22.6%, Phys. Status Solidi RRL 10, 583 (2016).
T. P. Weiss, F. Ehre, V. Serrano-Escalante, T. Wang, and S. Siebentritt, Understanding performance limitations of $Cu (In, Ga) {Se}_{2}$ solar cells due to metastable defects—A route toward higher efficiencies, Solar RRL 5, 2100063 (2021).
F. Babbe, L. Choubrac, and S. Siebentritt, The optical diode ideality factor enables fast screening of semiconductors for solar cells, Solar RRL 2, 1800248 (2018).
T. Wang, F. Ehre, T. P. Weiss, B. Veith-Wolf, V. Titova, N. Valle, M. Melchiorre, O. Ramírez, J. Schmidt, and S. Siebentritt, Diode factor in solar cells with metastable defects and back contact recombination, Adv. Energy Mater. n/a, 2202076 (2022).
T. Meyer, F. Engelhardt, J. Parisi, and U. Rau, Spectral dependence and Hall effect of persistent photoconductivity in polycrystalline $Cu (In, Ga) {Se}_{2}$ thin films, J. Appl. Phys. 91, 5093 (2002).
M. Igalson, M. Maciaszek, K. Macielak, A. Czudek, M. Edoff, and N. Barreau, Concentration of defects responsible for persistent photoconductivity in $Cu (In, Ga) {Se}_{2}$ : Dependence on material composition, Thin Solid Films 669, 600 (2019).
S. Lany and A. Zunger, Light- and bias-induced metastabilities in $Cu (In, Ga) {Se}_{2}$ based solar cells caused by the ( $VSe$ - $VCu$ ) vacancy complex, J. Appl. Phys. 100, 113725 (2006).
J. Bailey, G. Zapalac, and D. Poplavskyy, in Conference Record of the IEEE Photovoltaic Specialists Conference (2016), pp. 2135.
K. Decock, P. Zabierowski, and M. Burgelman, Modeling metastabilities in chalcopyrite-based thin film solar cells, J. Appl. Phys. 111, 043703 (2012).
K. Macielak, M. Maciaszek, M. Igalson, P. Zabierowski, and N. Barreau, Persistent photoconductivity in polycrystalline $Cu (In, Ga) {Se}_{2}$ thin films: Experiment versus theoretical predictions, IEEE J. Photovoltaics 5, 1206 (2015).
D. V. Lang and R. A. Logan, Large-Lattice-Relaxation Model for Persistent Photoconductivity in Compound Semiconductors, Phys. Rev. Lett. 39, 635 (1977).
K. Bothe, R. Hezel, and J. Schmidt, Recombination-enhanced formation of the metastable boron–oxygen complex in crystalline silicon, Appl. Phys. Lett. 83, 1125 (2003).
A. Nagaoka, D. Kuciauskas, and M. A. Scarpulla, Doping properties of cadmium-rich arsenic-doped $Cd Te$ single crystals: Evidence of metastable AX behavior, Appl. Phys. Lett. 111, 232103 (2017).
I. Mosquera-Lois, S. R. Kavanagh, A. Walsh, and D. O. Scanlon, “Identifying the ground state structures of point defects in solids” arXiv (2022). arXiv:2207.09862
H. Neumann and R. D. Tomlinson, Relation between electrical properties and composition in ${Cu In Se}_{2}$ single crystals, Solar Cells 28, 301 (1990).
O. Ramirez, E. M. Lanzoni, T. P. Weiss, R. Poeira, R. Leturcq, A. Redinger, and S. Siebentritt, How much gallium do we need for a p-type $Cu (In, Ga) {Se}_{2}$ ?, APL Mater. 10, 061108 (2022).
T. Trupke, R. A. Bardos, M. D. Abbott, and J. E. Cotter, Suns-photoluminescence: Contactless determination of current-voltage characteristics of silicon wafers, Appl. Phys. Lett. 87, 093503 (2005).
P. Wurfel, The chemical potential of radiation, J. Phys. C: Solid State Phys. 15, 3967 (1982).
P. Calado, D. Burkitt, J. Yao, J. Troughton, T. M. Watson, M. J. Carnie, A. M. Telford, B. C. O’Regan, J. Nelson, and P. R. F. Barnes, Identifying Dominant Recombination Mechanisms in Perovskite Solar Cells by Measuring the Transient Ideality Factor, Phys. Rev. Appl. 11, 044005 (2019).
P. Caprioglio, M. Stolterfoht, C. M. Wolff, T. Unold, B. Rech, S. Albrecht, and D. Neher, On the relation between the open-circuit voltage and quasi-Fermi level splitting in efficient perovskite solar cells, Adv. Energy Mater. 9, 1901631 (2019).
P. Caprioglio, C. M. Wolff, O. J. Sandberg, A. Armin, B. Rech, S. Albrecht, D. Neher, and M. Stolterfoht, On the origin of the ideality factor in perovskite solar cells, Adv. Energy Mater. 10, 2000502 (2020).
D. Kuciauskas, J. Moseley, P. Ščajev, and D. Albin, Radiative efficiency and charge-carrier lifetimes and diffusion length in polycrystalline $Cd Se Te$ heterostructures, Phys. Status Solidi RRL 14, 1900606 (2020).
R. Noufi, R. Axton, C. Herrington, and S. K. Deb, Electronic properties versus composition of thin films of ${Cu In Se}_{2}$ , Appl. Phys. Lett. 45, 668 (1984).
M. A. Contreras, J. Tuttle, A. Gabor, A. Tennant, K. Ramanathan, S. Asher, A. Franz, J. Keane, L. Wang, J. Scofield, and R. Noufi, in Conference Record of the IEEE Photovoltaic Specialists Conference (1994), pp. 68.
A. M. Gabor, J. R. Tuttle, D. S. Albin, M. A. Contreras, R. Noufi, and A. M. Hermann, High-efficiency ${Cu In}_{x} {Ga}_{1}$ _−xSe₂ solar cells made from $({In}_{x}, {Ga}_{1 - x})_{2} {Se}_{3}$ precursor films, Appl. Phys. Lett. 65, 198 (1994).
A. Kanevce, S. Paetel, D. Hariskos, and T. Magorian Friedlmeier, Impact of RbF-PDT on $Cu (In, Ga) {Se}_{2}$ solar cells with $Cd S$ and $Zn (O, S)$ buffer layers, EPJ Photovoltaics 11, 8 (2020).
S. Essig, S. Paetel, T. M. Friedlmeier, and M. Powalla, Challenges in the deposition of $(Ag, Cu) (In, Ga) {Se}_{2}$ absorber layers for thin-film solar cells, J. Phys.: Mater. 4, 024003 (2021).
M. H. Wolter, B. Bissig, E. Avancini, R. Carron, S. Buecheler, P. Jackson, and S. Siebentritt, Influence of sodium and rubidium postdeposition treatment on the quasi-Fermi level splitting of $Cu (In, Ga) {Se}_{2}$ thin films, IEEE J. Photovoltaics 8, 1320 (2018).
J. Nishinaga, T. Koida, S. Ishizuka, Y. Kamikawa, H. Takahashi, M. Iioka, H. Higuchi, Y. Ueno, H. Shibata, and S. Niki, Effects of long-term heat-light soaking on $Cu (In, Ga) {Se}_{2}$ solar cells with KF postdeposition treatment, Appl. Phys. Express 10, 092301 (2017).
T. Feurer, B. Bissig, T. P. Weiss, R. Carron, E. Avancini, J. Löckinger, S. Buecheler, and A. N. Tiwari, Single-graded CIGS with narrow bandgap for tandem solar cells, Sci. Technol. Adv. Mater. 19, 263 (2018).
T. Feurer, F. Fu, T. P. Weiss, E. Avancini, J. Löckinger, S. Buecheler, and A. N. Tiwari, RbF post deposition treatment for narrow bandgap $Cu (In, Ga) {Se}_{2}$ solar cells, Thin Solid Films 670, 34 (2019).
D. Regesch, L. Gütay, J. K. Larsen, V. Deprédurand, D. Tanaka, Y. Aida, and S. Siebentritt, Degradation and passivation of ${Cu In Se}_{2}$ , Appl. Phys. Lett. 101, 112108 (2012).
F. Babbe, L. Choubrac, and S. Siebentritt, Quasi Fermi level splitting of $Cu$ -rich and $Cu$ -poor $Cu (In, Ga) {Se}_{2}$ absorber layers, Appl. Phys. Lett. 109, 082105 (2016).
T. P. Weiss, B. Bissig, T. Feurer, R. Carron, S. Buecheler, and A. N. Tiwari, Bulk and surface recombination properties in thin film semiconductors with different surface treatments from time-resolved photoluminescence measurements, Sci. Rep. 9, 5385 (2019).
F. Pianezzi, P. Reinhard, A. Chirilă, B. Bissig, S. Nishiwaki, S. Buecheler, and A. N. Tiwari. Phys. Chem. Chem. Phys. 2014, 8843 (2014).
A. Czudek, A. Eslam, A. Urbaniak, P. Zabierowski, R. Wuerz, and M. Igalson, Evolution of the electrical characteristics of $Cu (In, Ga) {Se}_{2}$ devices with sodium content, J. Appl. Phys. 128, 173102 (2020).
O. Ramírez, M. Bertrand, A. Debot, D. Siopa, N. Valle, J. Schmauch, M. Melchiorre, and S. Siebentritt, The effect of potassium fluoride postdeposition treatments on the optoelectronic properties of $Cu (In, Ga) {Se}_{2}$ single crystals, Solar RRL 5, 2000727 (2021).
R. K. Ahrenkiel, Semiconductors and Semimetals (Academic Press, Boston, 1993), p. 39.
F. Werner, D. Colombara, M. Melchiorre, N. Valle, B. El Adib, C. Spindler, and S. Siebentritt, Doping mechanism in pure ${Cu In Se}_{2}$ , J. Appl. Phys. 119, 173103 (2016).
A. R. Burgers, J. A. Eikelboom, A. Schonecker, and W. C. Sinke, in Conference Record of the IEEE Photovoltaic Specialists Conference (1996), pp. 569.
T. P. Weiss, S. Nishiwaki, B. Bissig, R. Carron, E. Avancini, J. Löckinger, S. Buecheler, and A. N. Tiwari, Injection current barrier formation for RbF postdeposition-treated $Cu (In, Ga) {Se}_{2}$ -based solar cells, Adv. Mater. Interfaces 5, 1701007 (2018).
F. Werner, M. H. Wolter, S. Siebentritt, G. Sozzi, S. Di Napoli, R. Menozzi, P. Jackson, and W. Witte, “Alkalie treatment of $Cu (In, Ga) {Se}_{2}$ thin film absorbers: transport barriers and their influence on the admittance spectrum” unpublished (2017).
M. A. Green, Solar cell fill factors: General graph and empirical expressions, Solid-State Electron. 24, 788 (1981).
C.-M. Xu, X.-L. Xu, J. Xu, X.-J. Yang, J. Zuo, N. Kong, W.-H. Huang, and H.-T. Liu, Composition dependence of the Raman A 1 mode and additional mode in tetragonal $Cu$ – $In$ – $Se$ thin films, Semicond. Sci. Technol. 19, 1201 (2004).
S. Lany and A. Zunger, Metal-Dimer Atomic Reconstruction Leading to Deep Donor States of the Anion Vacancy in II–VI and Chalcopyrite Semiconductors, Phys. Rev. Lett. 93, 156404 (2004).
R. Scheer and H. W. Schock, Chalcogenide Photovoltaics: Physics, Technologies, and Thin Film Devices (Wiley-VCH Verlag & Co. KGaA, Weinheim, Germany, 2011).
D. Abou-Ras, N. Schäfer, N. Baldaz, S. Brunken, and C. Boit, Electron-beam-induced current measurements with applied bias provide insight to locally resolved acceptor concentrations at p–n junctions, AIP Adv. 5, 077191 (2015).
F. Werner, Hall measurements on low-mobility thin films, J. Appl. Phys. 122, 135306 (2017).
A. Klein, Energy band alignment in chalcogenide thin film solar cells from photoelectron spectroscopy, J. Phys.: Condens. Matter 27, 134201 (2015).
T. Walter, R. Herberholz, and H. W. Schock, Distribution of defects in polycrytalline chalcopyrite thin films, Solid State Phenomena 51–52, 309 (1996).
C. van Berkel, M. J. Powell, A. R. Franklin, and I. D. French, Quality factor in a- $Si$ :H nip and pin diodes, J. Appl. Phys. 73, 5264 (1993).
M. H. Wolter, R. Carron, E. Avancini, B. Bissig, T. P. Weiss, S. Nishiwaki, T. Feurer, S. Buecheler, P. Jackson, W. Witte, and S. Siebentritt, How band tail recombination influences the open-circuit voltage of solar cells, Prog. Photovoltaics 30, 702 (2022).
S. J. Heise and J. F. López Salas, Charge separation effects in time-resolved photoluminescence of $Cu (In, Ga) {Se}_{2}$ thin film solar cells, Thin Solid Films 633, 35 (2017).
W. K. Metzger, I. L. Repins, M. Romero, P. Dippo, M. Contreras, R. Noufi, and D. Levi, Recombination kinetics and stability in polycrystalline $Cu (In, Ga) {Se}_{2}$ solar cells, Thin Solid Films 517, 2360 (2009).
M. Edoff, T. Jarmar, N. S. Nilsson, E. Wallin, D. Högström, O. Stolt, O. Lundberg, W. Shafarman, and L. Stolt, High V_oc in ( $Cu, Ag) (In, Ga) {Se}_{2}$ solar cells, IEEE J. Photovoltaics 7, 1789 (2017).
I. Repins, M. A. Contreras, B. Egaas, C. DeHart, J. Scharf, C. L. Perkins, B. To, and R. Noufi, 19.9%-efficient $Zn O / Cd S / {Cu In Ga Se}_{2}$ solar cell with 81.2% fill factor, Prog. Photovoltaics 16, 235 (2008).

Phys. Rev. Applied 19, 024052– Published 17 February, 2023

Vol. 19, Iss. 2 — February 2023

Received 27 April 2022
Revised 5 December 2022
Accepted 10 January 2023

DOI: https://doi.org/10.1103/PhysRevApplied.19.024052

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Physical Review Applied

Reuse & Permissions

Export citation

Export citation

Metastable Defects Decrease the Fill Factor of Solar Cells

Abstract

Physics Subject Headings (PhySH)

Collections

Photovoltaic Energy Conversion

Article Text

References (61)

Outline

Information

Filter

Filter

Article Lookup

Enter a citation