Residual strain engineering in seed layer assisted Kesterite Cu2ZnSnS4 absorber layer

Abstract

Narrow-phase stability of CZTS often leads to the formation of secondary phases and defects that eventually results in disorder in the crystal structure. Moreover, lattice-mismatch and thermal stress at CZTS/Mo interface nourish strained growth, which adversely affects the Cu-Zn ordering in CZTS. Thus far, understanding and evolution of these residual strains and their influence on the optoelectronic properties of CZTS are lacking. Herein, we probed the residual strain along penetration depth and demonstrated a facile approach of tailoring lattice strain in CZTS. High quality CZTS films with seed layer (SL) growth are developed to investigate residual strain distribution using depth-dependent grazing incidence X-ray diffraction (GIXRD) measurements. A graded strain has been identified in SL films than uniformly strained no SL films. Besides improvement in Cu-Zn order, Photoluminescence (PL) signal in SL films was substantially quenched by 55.3%, which is ascribed to the charge transfer as a consequence of graded strain. Graded strain in SL films tends to form multi-homojunction, influencing charge carrier dynamics, resulting in a 36-fold increase in photocurrent and approximately 5 times faster response over No SL CZTS based device.