Copper zinc tin sulfide layers prepared from solution processable metal dithiocarbamate precursors

Abstract

In this contribution we present a solution based route toward copper zinc tin sulfide – CZTS – layers using metal dithiocarbamate precursors. We focus on the synthesis of the precursor materials as well as on the fabrication of thin CZTS layers at low temperatures of 350 °C and their characterization. Powder X-ray diffraction measurements show that a precursor solution containing an excess of the zinc precursor, compared to the Cu and Sn precursors, has to be used to obtain CZTS films without secondary phases. Thus, the prepared films are Zn-rich, which is beneficial for solar cell applications. Raman as well as X-ray photoelectron spectroscopy studies confirm the formation of CTZS. No clear evidence for free ZnS has been found. Electron microscopy shows agglomerates of 10 nm-sized crystallites forming spherical particles with a diameter between 50 nm and 400 nm. The prepared films possess high optical absorption (>1.104 cm−1) and an optical band gap of approximately 1.6 eV.