title: Deliberate and Accidental Gas-Phase Alkali Doping of Chalcogenide Semiconductors: Cu(In,Ga)Se2.
abstract: Alkali metal doping is essential to achieve highly efficient energy conversion in Cu(In,Ga)Se2(CIGSe) solar cells. Doping is normally achieved through solid state reactions, but recent observations of gas-phase alkali transport in the kesterite sulfide (Cu2ZnSnS4) system (re)open the way to a novel gas-phase doping strategy. However, the current understanding of gas-phase alkali transport is very limited. This work (i) shows that CIGSe device efficiency can be improved from 2% to 8% by gas-phase sodium incorporation alone, (ii) identifies the most likely routes for gas-phase alkali transport based on mass spectrometric studies, (iii) provides thermochemical computations to rationalize the observations and (iv) critically discusses the subject literature with the aim to better understand the chemical basis of the phenomenon. These results suggest that accidental alkali metal doping occurs all the time, that a controlled vapor pressure of alkali metal could be applied during growth to dope the semiconductor, and that it may have to be accounted for during the currently used solid state doping routes. It is concluded that alkali gas-phase transport occurs through a plurality of routes and cannot be attributed to one single source.
authors.affiliation: University of Luxembourg, Physics and Materials Science Research Unit. 41, rue du Brill, L-4422 Belvaux, Luxembourg.
authors.forename: Diego
authors.initials: D
authors.lastname: Colombara
authors.affiliation: Robert Bosch GmbH, Corporate Sector Research and Advance Engineering, Robert Bosch Campus 1, D-71272 Renningen, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Berner
authors.affiliation: Università la Sapienza di Roma, Dipartimento di Chimica, Piazzale Aldo Moro 5 00185 Roma, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Ciccioli
authors.affiliation: Department of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44-bus 2450, B-3001 Leuven, Belgium.
authors.forename: João C
authors.initials: JC
authors.lastname: Malaquias
authors.affiliation: University of Luxembourg, Physics and Materials Science Research Unit. 41, rue du Brill, L-4422 Belvaux, Luxembourg.
authors.forename: Tobias
authors.initials: T
authors.lastname: Bertram
authors.affiliation: University of Luxembourg, Physics and Materials Science Research Unit. 41, rue du Brill, L-4422 Belvaux, Luxembourg.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Crossay
authors.affiliation: NETZSCH-Gerätebau GmbH, Wittelsbacherstraße 42 D-95100 Selb/Bayern, Germany.
authors.forename: Michael
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authors.lastname: Schöneich
authors.affiliation: University of Luxembourg, Physics and Materials Science Research Unit. 41, rue du Brill, L-4422 Belvaux, Luxembourg.
authors.forename: Helene J
authors.initials: HJ
authors.lastname: Meadows
authors.affiliation: University of Luxembourg, Physics and Materials Science Research Unit. 41, rue du Brill, L-4422 Belvaux, Luxembourg.
authors.forename: David
authors.initials: D
authors.lastname: Regesch
authors.affiliation: Università degli Studi di Genova, Dipartimento di Chimica e Chimica Industriale, Via Dodecaneso 31 16146 Genova, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Delsante
authors.affiliation: Università la Sapienza di Roma, Dipartimento di Chimica, Piazzale Aldo Moro 5 00185 Roma, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Gigli
authors.affiliation: Luxembourg Institute of Science and Technology, 41, rue du Brill, L-4422 Belvaux, Luxembourg.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Valle
authors.affiliation: Luxembourg Institute of Science and Technology, 41, rue du Brill, L-4422 Belvaux, Luxembourg.
authors.forename: Jérome
authors.initials: J
authors.lastname: Guillot
authors.affiliation: Luxembourg Institute of Science and Technology, 41, rue du Brill, L-4422 Belvaux, Luxembourg.
authors.forename: Brahime
authors.initials: B
authors.lastname: El Adib
authors.affiliation: Luxembourg Institute of Science and Technology, 41, rue du Brill, L-4422 Belvaux, Luxembourg.
authors.forename: Patrick
authors.initials: P
authors.lastname: Grysan
authors.affiliation: University of Luxembourg, Physics and Materials Science Research Unit. 41, rue du Brill, L-4422 Belvaux, Luxembourg.
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Dale