Role of carbon quantum dot for enhanced performance of photo-absorption in Cu2CoSnS4 superstrate solar cell device

In the present work, superstrate type ITO/CdS/Cu2CoSnS4 (CCTS) and Cu2CoSnS4:CQD (CCTS:CQDs)/Al thin-film solar cells are reported. An attempt was made to fabricate CCTS and CCTS:CQD thin-film absorbers using spray pyrolysis at a deposition temperature of 170 degrees C. In order to increase the crystallization performance, thin films were annealed at 250 degrees C for 30 min under N-2 atmosphere using rapid thermal annealing. The XRD results showed the formation of the stannite structure for both CCTS and CCTS:CQD and the phase purity was confirmed by Raman analysis. The XPS spectra indicated oxidation states of Cu, Co, Sn, and S to be Cu+, Co2+, Sn4+, and S2- in CCTS and CCTS:CQD films. The band gap of the films was obtained as 1.35 and 1.26 eV for CCTS and CCTS:CQD. The CCTS:CQD device shows an improved efficiency (0.07%) over the CCTS device (0.003%). Impedance measurement was performed to analyze the interface between contacts and the bulk. These results showed that carbon quantum-dot-based chalcogenides can effectively absorb UV-visible photons and separate electrons and holes as potential candidates for future low-cost large-area inorganic solar cells.

Automated summary

This study reports the fabrication and characterization of superstrate type ITO/CdS/Cu2CoSnS4 (CCTS) and Cu2CoSnS4:CQD (CCTS:CQDs)/Al thin-film solar cells using spray pyrolysis. The crystallization performance, phase purity, and band gap of the CCTS and CCTS:CQD thin films were investigated. The comparison of efficiency between the two devices showed that the CCTS:CQD device exhibited improved performance. Impedance measurement was performed to analyze the interface between contacts and the bulk material. These results suggest that carbon quantum-dot-based chalcogenides have potential as candidates for future low-cost large-area inorganic solar cells.