Abstract:
Cu2ZnSnS4 (CZTS) solar cells suffer from lower power conversion efficiency relative to its fellow copper indium gallium selenide thin-film
technology, which have been asserted on the existence of non-stoichiometry and high degree of Cu–Zn disorder. Huge disparity among the
lattice constants of Mo and CZTS is one of the causes of inducing strain in the film, which often creates defects in the CZTS structure. This
work focused on investigating the effect of strain modulation using seed layer (SL) assisted growth on the structural and optoelectronic properties of CZTS films. The results indicate that SL growth of CZTS reduces strain in the film and improves the crystallinity and overall quality
of the CZTS absorber, as indicated by SEM and x-ray diffraction studies. Raman shifts to higher wavenumber and photoluminescence (PL)
energy shift corresponding to dominant band-to-band transition in SL CZTS correlate perfectly with the high value of order parameter.
Bandgap enhancement and reduction in the Urbach energy of SL CZTS implicate higher ordering (reduction in Cu–Zn disorder) due to
strain modulation. Consequently, substantial improvement from 2.13 to 13.5 cm2
/V s in hole mobility is achieved. Finally, the faster response
of the photodetector based on SL CZTS compared to without SL growth supports all the findings. Our results imply that SL assisted growth
of CZTS could be critical to obtain a high-quality CZTS absorber layer.
