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Experimental and theoretical study into interface structure and band alignment of the Cu2Zn1–xCdxSnS4 heterointerface for photovoltaic applications

Rondiya, Sachin R., Jadhav, Yogesh, Dzade, Nelson Y., Ahammed, Raihan, Goswami, Tanmay, De Sarkar, Abir, Jadkar, Sandesh, Haram, Santosh and Ghosh, Hirendra N. 2020. Experimental and theoretical study into interface structure and band alignment of the Cu2Zn1–xCdxSnS4 heterointerface for photovoltaic applications. ACS Applied Energy Materials 3 (6) , pp. 5153-5162. 10.1021/acsaem.9b02314

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Abstract

To improve the constraints of kesterite Cu2ZnSnS4 (CZTS) solar cell, such as undesirable band alignment at p–n interfaces, bandgap tuning, and fast carrier recombination, cadmium (Cd) is introduced into CZTS nanocrystals forming Cu2Zn1–xCdxSnS4 through cost-effective solution-based method without postannealing or sulfurization treatments. A synergetic experimental–theoretical approach was employed to characterize and assess the optoelectronic properties of Cu2Zn1–xCdxSnS4 materials. Tunable direct band gap energy ranging from 1.51 to 1.03 eV with high absorption coefficient was demonstrated for the Cu2Zn1–xCdxSnS4 nanocrystals with changing Zn/Cd ratio. Such bandgap engineering in Cu2Zn1–xCdxSnS4 helps in effective carrier separation at interface. Ultrafast spectroscopy reveals a longer lifetime and efficient separation of photoexcited charge carriers in Cu2CdSnS4 (CCTS) nanocrystals compared to that of CZTS. We found that there exists a type-II staggered band alignment at the CZTS (CCTS)/CdS interface, from cyclic voltammetric (CV) measurements, corroborated by first-principles density functional theory (DFT) calculations, predicting smaller conduction band offset (CBO) at the CCTS/CdS interface as compared to the CZTS/CdS interface. These results point toward efficient separation of photoexcited carriers across the p–n junction in the ultrafast time scale and highlight a route to improve device performances.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Publisher: American Chemical Society
ISSN: 2574-0962
Funders: EPSRC
Date of First Compliant Deposit: 16 June 2020
Date of Acceptance: 5 May 2020
Last Modified: 05 Aug 2020 12:04
URI: http://orca-mwe.cf.ac.uk/id/eprint/132481

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