Bandgap engineering of Cu2Sn(S,Se)3 semiconductor nanocrystals and their applications in thin film solar cells

The energy bandgap of semiconductors determines the optical spectrum response of absorber materials, which is one of the vital physical parameters that impact the band alignment of a solar cell's p-n junction. Therefore, the bandgap engineering of absorber materials is essential in that it influences directly the open current voltage and the power conversion efficiency of solar cells. In this paper, the bandgap engineering of Cu2Sn(S,Se)3 (CTSSe) nanocrystals (NCs) were achieved by controlling the ratio of sulfur and selenium in solid solution NCs. The bandgaps of CTSSe NCs were tuned approximately linearly from 1.20 to 1.52 eV by increasing the sulfur and selenium atomic ratio. Moreover, the dense and compact CTSSe absorbers with good crystallization and large grains can be acquired by non-vacuum CTS NCs deposition method. Finally, a typical CTSSe thin film solar cell with power conversion efficiency of 0.89% was acquired according to the traditional structure of thin film solar cells.