Pulsed laser deposition of a Bi2S3/CuInS2/TiO2 cascade structure for high photoelectrochemical performance

Abstract

The PLD technique is used for the direct fabrication of QD sensitized solar cells (QDSSCs) without any encapsulation and/or resorting to any surface treatment, ligand engineering and/or post-synthesis processing which might involve some toxic chemical regents harmful to the performance of solar cells. In this paper, co-sensitizers of Bi₂S₃ and CuInS₂ quantum dots (QDs) are deposited on TiO₂ nanorods via a physical deposition-based pulsed laser deposition (PLD) technique to fabricate the cascade structure of Bi₂S₃/CuInS₂/TiO₂. The performance of the QDSSCs with a cascade structure is optimized by adjusting the laser energy, and an energy conversion efficiency of 4.81% is achieved under one sun illumination (AM 1.5, 100 mW cm⁻²). Besides, the photovoltaic device exhibits high stability in air without any specific encapsulation. The improved performance is attributed to enhanced absorption in the longer wavelength region, quicker interfacial charge transfer and less chance of electron recombination with holes. Moreover, the direct atomic contact by the PLD technique and the cascade structure are also favorable factors for the enhanced photoelectrochemical performance of QDSSCs.