Heavy Alkali Treatment of Cu(In,Ga)Se-2 Solar Cells: Surface versus Bulk Effects

Siebentritt S, Avancini E, Bär M, Bombsch J, Bourgeois E, Buecheler S, Carron R, Castro C, Duguay S, Felix R, Handick E, Hariskos D, Havu V, Jackson P, Komsa HP, Kunze T, Malitckaya M, Menozzi R, Nesladek M, Nicoara N, Puska M, Raghuwanshi M, Pareige P, Sadewasser S, Sozzi G, Tiwari AN, Ueda S, Vilalta-Clemente A, Weiss TP, Werner F, Wilks RG, Witte W, Wolter MH (2020)

Publication Type: Journal article

Publication year: 2020

Journal

Advanced Energy Materials Wiley

DOI: 10.1002/aenm.201903752

Abstract

Chalcopyrite solar cells achieve efficiencies above 23%. The latest improvements are due to post-deposition treatments (PDT) with heavy alkalis. This study provides a comprehensive description of the effect of PDT on the chemical and electronic structure of surface and bulk of Cu(In,Ga)Se-2. Chemical changes at the surface appear similar, independent of absorber or alkali. However, the effect on the surface electronic structure differs with absorber or type of treatment, although the improvement of the solar cell efficiency is the same. Thus, changes at the surface cannot be the only effect of the PDT treatment. The main effect of PDT with heavy alkalis concerns bulk recombination. The reduction in bulk recombination goes along with a reduced density of electronic tail states. Improvements in open-circuit voltage appear together with reduced band bending at grain boundaries. Heavy alkalis accumulate at grain boundaries and are not detected in the grains. This behavior is understood by the energetics of the formation of single-phase Cu-alkali compounds. Thus, the efficiency improvement with heavy alkali PDT can be attributed to reduced band bending at grain boundaries, which reduces tail states and nonradiative recombination and is caused by accumulation of heavy alkalis at grain boundaries.

Authors with CRIS profile

Marcus Bär Professur für Röntgenspektroskopie (HIERN)

Involved external institutions

University of Luxembourg LU Luxembourg (LU) University of Parma / Università degli Studi di Parma IT Italy (IT) Zentrum für Sonnenenergie- und Wasserstoff-Forschung (ZSW) DE Germany (DE) Université de Caen Basse-Normandie FR France (FR) Hasselt University / Universiteit Hasselt BE Belgium (BE) Aalto University Espoo FI Finland (FI) Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) DE Germany (DE) Eidgenössische Materialprüfungs- und Forschungsanstalt (Empa) / Swiss Federal Laboratories for Materials Science & Technology CH Switzerland (CH) National Institute of Materials Science (NIMS) JP Japan (JP) INL - International Iberian Nanotechnology Laboratory PT Portugal (PT)

How to cite

APA:

Siebentritt, S., Avancini, E., Bär, M., Bombsch, J., Bourgeois, E., Buecheler, S.,... Wolter, M.H. (2020). Heavy Alkali Treatment of Cu(In,Ga)Se-2 Solar Cells: Surface versus Bulk Effects. Advanced Energy Materials. https://dx.doi.org/10.1002/aenm.201903752

MLA:

Siebentritt, Susanne, et al. "Heavy Alkali Treatment of Cu(In,Ga)Se-2 Solar Cells: Surface versus Bulk Effects." Advanced Energy Materials (2020).

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