Solution-processed nanomaterials for applications in photoelectrochemical solar cells

• Main Author: Zhang, Xuemei
• Other Authors: Riley, Jason
• Published: Imperial College London 2015
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.739549

Quaternary Cu2ZnSnS4 (CZTS) and binary Bi2S3 are considered as potential photovoltaic materials due to their suitable electronic and optical properties, low-toxicity and earth-abundant elemental constitution. This thesis investigates the preparation of CZTS and Bi2S3 nanocrystals in solution-based approaches and examines their applicability in photoelectrochemical solar cells with an aim of fabricating low-cost photovoltaics. CZTS nanocrystals with the kesterite crystal structure were prepared by a hot-injection method in which elemental sulfur was used as the sulfur source. The synthetic conditions were optimized in order to obtain high-quality CZTS particles. The kesterite CZTS nanocrystals were explored as both the sensitizers in photoanode and the building blocks for fabricating thin films. CZTS sensitized TiO2 thin films were used as photoanodes in semiconductor sensitized solar cells (SSSCs); CZTS nanocrystal thin films were employed as photocathodes in dye sensitized solar cells (DSSCs). In addition, wurtzite CZTS nanocrystals were also synthesized by a hot-injection method in which an alternative sulfur source, dodecanethiol, was used. In order to examine the influence of metal nanoparticles on the performance of CZTS photocathodes, Au nanoparticles were introduced in the synthesis which led to the formation of core-shell Au@wurtzite CZTS nanoparticles. The performance of those core-shell nanoparticles as a photocathode material was tested in DSSCs. A novel method was developed for the in-situ preparation and deposition of Bi2S3 nanocrystals in the porous TiO2 thin films. Photoresponse studies showed that the in-situ generated Bi2S3 nanoparticles function as good sensitizers to TiO2 thin films. The Bi2S3 sensitized TiO2 thin films were investigated as photoanodes in SSSCs.