Investigation of the properties of CZTS/FTO interface

Fluorine doped tin oxide (FTO) has low lattice mismatch with Cu2ZnSnS4 (CZTS) thin film and has been considered as a suitable substrate material for CZTS. The interface properties between CZTS and FTO play an important role in the photovoltaic performance of CZTS thin film solar cells. However, studies on the properties of the CZTS/FTO interface are scarce. In this work, the phase structures, compositions, morphologies, and electrical contact properties of the CZTS/FTO interfaces were investigated. CZTS thin films with annealing temperature from 500 °C to 580 °C were deposited on FTO-coated glass substrate by sol-gel, spin-coating, and annealing processes. The CZTS/FTO interfaces were characterized by X-ray diffraction, Raman spectroscopy, energy-dispersive spectroscopy, secondary ion mass spectroscopy, scanning electron microscopy, resistivity, and current–voltage (I–V) characteristic curve measurement. The results show the successful formation of CZTS/FTO interfaces. No interfacial layer was found at all the CZTS/FTO interfaces, indicating the stability of the CZTS/FTO interface during high temperature treatment. The I–V curves of all the CZTS/FTO structures were near linear, revealing the formation of ohmic contact between CZTS and FTO. The experimental results in this work indicate the feasibility of FTO as a substrate and back electrode for CZTS thin films.