Mapping Shunting Paths at the Surface of Cu2ZnSn(S,Se)4 Films via Energy-Filtered Photoemission Microscopy
Devendra Tiwari,
Mattia Cattelan,
Robert L. Harniman,
Andrei Sarua,
Ali Abbas,
Jake W. Bowers,
Neil A. Fox,
David J. Fermin
Affiliations
Devendra Tiwari
School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
Mattia Cattelan
School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
Robert L. Harniman
School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
Andrei Sarua
H H Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, UK
Ali Abbas
Centre for Renewable Energy Systems Technology (CREST), Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough LE11 3TU, UK
Jake W. Bowers
Centre for Renewable Energy Systems Technology (CREST), Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough LE11 3TU, UK
Neil A. Fox
School of Chemistry, University of Bristol, Bristol BS8 1TS, UK; H H Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, UK
David J. Fermin
School of Chemistry, University of Bristol, Bristol BS8 1TS, UK; Corresponding author
Summary: The performance of Cu2ZnSn(S,Se)4 thin-film solar cells, commonly referred to as kesterite or CZTSSe, is limited by open-circuit voltage (VOC) values less than 60% of the maximum theoretical limit. In the present study, we employ energy-filtered photoemission microscopy to visualize nanoscale shunting paths in solution-processed CZTSSe films, which limit the VOC of cells to approximately 400 mV. These studies unveil areas of local effective work function (LEWF) narrowly distributed around 4.9 eV, whereas other portions show hotspots with LEWF as low as 4.2 eV. Localized valence band spectra and density functional theory calculations allow rationalizing the LEWF maps in terms of the CZTSSe effective work function broadened by potential energy fluctuations and nanoscale Sn(S,Se) phases. : Chemistry; Materials Science; Energy Materials Subject Areas: Chemistry, Materials Science, Energy Materials
