Phase-controlled CuInS2 nanocrystals synthesized by an ambient pressure polylol-based solution process and their photovoltaic application

• CuInS2 nanocrystals were synthesized by a triethylene glycol based solution route.
• Zincblende or wurtzite CuInS2 can be controlled by changing the sulfur sources.
• Conversion efficiency of 1.02% were obtained using by zincblende CIS thin films.

Pure-phase zincblende and wurtzite CuInS2 nanocrystals were synthesized by an environment-friendly, low-cost, ambient pressure triethylene glycol based solution route. Structure, morphology, chemical stoichiometry and optical property of the synthesized nanocrystals with different crystalline structure were characterized. The average size is 11.6 nm for zincblende CuInS2 nanoparticles with size distribution ranged from 5.4 nm to 19.6 nm, and a broad size distribution ranged from 20 nm to 150 nm is for wurtzite CuInS2 nanoplates. Both zincblende and wurtzite CuInS2 have stoichiometric composition and strong absorption over the entire visible light spectrum and near infrared region. The synthesized CuInS2 nanocrystals were applied to prepare ethanol-based colloidal ink and then deposit thin films by dip-coating process. The synthesized thin films were annealed at 550 °C in a selenization atmosphere. A power conversion efficiency of ~1.02% has been achieved by using zincblende CuInS2 nanocrystals as ink.