Spray-coated organic ligand-free Cu₂ZnSnS₄ nanoparticle thin film solar cells

Description

The efficiency of pure-sulfide Cu₂ZnSnS₄ (CZTS) photovoltaics is on a steady raise, and solution-processing methods are needed for upscaling technologies in the future. Among them, spray-coating offers large-area deposition, minimal material losses, and an automated setup. In this work, we synthesize organic ligand-free CZTS nanoparticles (NPs) according to our earlier work [1], and formulate an ink consisting of water and ethanol. This allows inclusion of new elements e.g. Ag, Ba, and alkali elements in the form of Cl-salts, and we have seen particularly beneficial effects with K [2].
A Nadetech spray-system is used, which utilizes ultrasonic atomization and includes an ultrasonic syringe pump. The ultrasonic waves ensure well-dispersed NPs, which leads to a more uniform film. Moreover, forming a flat film depends on NP size distribution as well as a complicated relation between substrate temperature, droplet size, and nozzle height.
The as-deposited films are annealed and when appropriate completed into full solar cell devices. The morphology is characterized by scanning electron microscopy and profilometry, and film quality via photoluminescence.
[1] N. Mirbagheri, S. Engberg, et al., Synthesis of ligand-free CZTS nanoparticles via a facile hot injection route, Nanotechnology, 27 (2016).
[2] S. Engberg et al., Liquid phase assisted grain growth in Cu₂ZnSnS₄ nanoparticle thin films by alkali element incorporation, RSC Advances, 8 (2018).

Period	30 May 2019
Held at	European Materials Research Society, France