Mapping shunting paths at the surface of Cu2ZnSn(S,Se)4 films via energy filtered photoemission microscopy
journal contributionposted on 09.11.2018 by Devendra Tiwari, Mattia Cattelan, Robert L. Harniman, Andrei Sarua, Ali Abbas, Jake Bowers, Neil A. Fox, David J. Fermin
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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 400mV. 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.
D.T., A.A., J.W.B., and D.J.F. acknowledge support from the Engineering and Physical Sciences Research Council (EPSRC) through the PVTEAM consortium (EP/L017792/1). N.A.F. and M.C. acknowledge funding from the EPSRC’s Strategic Equipment Panel for the Bristol NanoESCA II (grants EP/K035746/1, EP/M000605/1).
- Mechanical, Electrical and Manufacturing Engineering