Impact of Sb and Na Doping on the Surface Electronic Landscape of Cu2ZnSnS4 Thin Films

Devendra Tiwari, Mattia Cattelan, Robert L. Harniman, Andrei Sarua, Neil Fox, Tristan Koehler, Reiner Klenk, David J. Fermin

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Abstract

Open-circuit voltage deficiency is the key limiting factor in Cu2ZnSnS4 (CZTS) thin-film solar cells, which is commonly associated with band tails and deep gap states arising from elemental disorder. The introduction of dopants such as Na and Sb has led to improvement in device performance, yet their effects on the optoelectronic properties of CZTS are yet to be fully elucidated. In this Letter, we unraveled the effect of Sb and Na:Sb co-doping on the surface energy landscape of solution-processed CZTS films employing energy-filtered photoelectron emission microscopy. In the absence of the additives, 150 nm resolution photoemission maps reveal oscillations in the local effective work function as well as areas of low photoemission energy threshold. The introduction of dopants substantially reshapes the photoemission maps, which we rationalize in terms of Cu:Zn and Sn disorder. Finally, we establish unprecedented correlations between the photoemission landscape of thin films and the performance of over 200 devices.
Original languageEnglish
Pages (from-to)2977-2982
JournalACS Energy Letters
Volume3
Issue number12
Early online date14 Nov 2018
DOIs
Publication statusPublished - 14 Dec 2018
Externally publishedYes

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