CZTS Solar Cells From Abundant Element
Our research aims to increase the performance of solar cells by optimising the manufacturing process and materials.
CZTS — solceller från vanliga grundämnen.
CZTS is an abbreviation of Cu2ZnSn(S,Se)4, a material crystallizing in the kesterite structure, composed of only abundant and non-toxic elements. CZTS has the potential advantage of lower cost and more reliable access to material as compared to for example CIGS with indium and CdTe with tellurium. However, the device efficiency is still too low to compete with existing technologies. The main limitation is a lower-than-expected open circuit voltage, coupled to intrinsic defects.
Our work on CZTS comprises all parts from thin film growth processes and materials characterization to device engineering and characterization. We focus on absorber film growth using sputtering followed by annealing in sulfur and/or selenium containing atmosphere. Both reactive sputtering from metallic targets in Ar/H2S and compound co-sputtering from sulfide or selenide targets have been studied. Engineering of the front and back contacts has been explored with best solar cell results achieved using Zn1-xSnxOy (ZTO) buffer layers deposited by atomic layer deposition instead of the standard CdS film. Best device results are obtained with the standard opaque Mo back contact, but for semitransparent solar cells, transparent conductive back contact with interface barrier layers can instead be used.
The absorber band gap can be tuned through alloying with Ge (higher band gap) or Se (lower band gap) and some recent results in our lab indicated that record open circuit voltage (1.1 V) can be obtained for wide band gap full germanium kesterite Cu2ZnGeS4 (CZGS) thin film solar cells by using ZTO buffer layer. Attempts to form band gap gradients for improved carrier collection using S/Se or Sn/Ge gradients has also been explored but did not result in device improvements so far.
Contact: Charlotte Platzer-Björkman
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- Record 1.1V open-circuit voltage for Cu2ZnGeS4-based thin film solar cells using atomic layer deposition Zn1-xSnxOy buffer layers. N Saini, N Martin, J Larsen, A Hultqvist, C Platzer Björkman, Solar RRL, 6(2) 2100837 (2022).
- Band tails and Cu-Zn Disorder in Cu2ZnSnS4 Solar Cells. JK Larsen, JJS Scragg, N Ross, C Platzer-Björkman, ACS Applied Energy Materials 3 (8), 7520-7526 (2020).
- Reduced interface recombination in Cu2ZnSnS4 solar cells with atomic layer deposition Zn1-xSnxOy buffer layers. C Platzer-Björkman, C Frisk, JK Larsen, T Ericson, SY Li, JJS Scragg, J. Keller, F. Larsson, T. Törndahl, Applied Physics Letters 107 (24) (2015).
- A low-temperature order-disorder transition in Cu2ZnSnS4 thin films. J. S. Scragg; L Choubrac; A Lafond; T Ericson; C Platzer-Björkman, Appl. Phys. Lett. 104, 041911 (2014).