Slurry-based processing of high-performance CZTSSe photovoltaic absorber layers

Abstract

Kesterite Cu2ZnSnS4-ySey (CZTSSe) materials are considered promising for application as thin-film photovoltaic (PV) absorber layers because of appropriate band gap (ranging from 1.0-1.5 eV, as a function of y) and low-cost, readily-available constituents. This talk will focus on a simple particle-based approach for solution processing device quality CZTSSe films. Deposition involves three steps: 1) preparation of the hydrazine-based CZTSSe precursor slurry, 2) liquid-processing (e.g., spin coating or doctor blading) of CZTSSe precursor films on an appropriate substrate, and 3) heat treating to yield the desired CZTSSe layer. High quality films with variable sulfur to selenium ratio (y) are deposited using this approach. PV devices based on a glass/Mo/CZTSSe/CdS/i-ZnO/ITO structure and employing the slurry-processed CZTSSe layer with y > 2 (i.e., Se rich) have yielded independently-certified power conversion efficiencies of >9.5% (AM 1.5 illumination), a record for the kesterite family of materials. Recent results using this approach will be discussed.