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Heavy Alkali Treatment of Cu(In,Ga)Se 2 Solar Cells: Surface versus Bulk Effects
Author(s) -
Siebentritt Susanne,
Avancini Enrico,
Bär Marcus,
Bombsch Jakob,
Bourgeois Emilie,
Buecheler Stephan,
Carron Romain,
Castro Celia,
Duguay Sebastien,
Félix Roberto,
Handick Evelyn,
Hariskos Dimitrios,
Havu Ville,
Jackson Philip,
Komsa HannuPekka,
Kunze Thomas,
Malitckaya Maria,
Menozzi Roberto,
Nesladek Milos,
Nicoara Nicoleta,
Puska Martti,
Raghuwanshi Mohit,
Pareige Philippe,
Sadewasser Sascha,
Sozzi Giovanna,
Tiwari Ayodhya Nath,
Ueda Shigenori,
VilaltaClemente Arantxa,
Weiss Thomas Paul,
Werner Florian,
Wilks Regan G.,
Witte Wolfram,
Wolter Max Hilaire
Publication year - 2020
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201903752
Subject(s) - grain boundary , materials science , band bending , alkali metal , recombination , solar cell , chemical physics , chalcopyrite , grain size , microstructure , optoelectronics , composite material , metallurgy , copper , chemistry , biochemistry , organic chemistry , gene
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.