Photoluminescence study of disordering in the cation sublattice of Cu2ZnSnS4

• Post-synthesis cooling rate enables to control the degree of ordering in Cu2ZnSnS4.
• Temperature dependent photoluminescence of Cu2ZnSnS4 was studied.
• In rapidly cooled CZTS recombination involving defect clusters dominates at T = 10 K.
• In slowly cooled CZTS band-to-impurity recombination dominates at T = 10 K.

In this study we investigated the influence of the degree of disordering in the cation sublattice on low temperature photoluminescence (PL) properties of Cu2ZnSnS4 (CZTS) polycrystals. The degree of disordering was changed by using different cooling rates after post-annealing at elevated temperatures. The results suggest that in the case of higher degree of cation sublattice disorder radiative recombination involving defect clusters dominates at T = 10 K. These defect clusters induce local band gap energy decrease in CZTS. The concentration of defect clusters can be reduced by giving more time for establishing ordering in the crystal lattice. As a result, radiative recombination mechanism changes and band-to-impurity recombination involving deep acceptor defect with ionization energy of about 200 meV starts to dominate in the low temperature PL spectra of CZTS polycrystals.