Experimental and Theoretical Study into Interface Structure and Band Alignment of the Cu2Zn1-xCdxSnS4Heterointerface for Photovoltaic Applications

Sachin R. Rondiya, Yogesh Jadhav, Nelson Y. Dzade, Raihan Ahammed, Tanmay Goswami, Abir De Sarkar, Sandesh Jadkar, Santosh Haram, Hirendra N. Ghosh

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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.

Original languageEnglish (US)
Pages (from-to)5153-5162
Number of pages10
JournalACS Applied Energy Materials
Issue number6
StatePublished - Jun 22 2020

All Science Journal Classification (ASJC) codes

  • Chemical Engineering (miscellaneous)
  • Energy Engineering and Power Technology
  • Electrochemistry
  • Materials Chemistry
  • Electrical and Electronic Engineering

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