Anatase TiO2 nanosheets with exposed highly reactive (001) facets as an efficient photoanode for quantum dot-sensitized solar cells

Abstract

Two-dimensional (2D) anatase TiO₂ nanosheets (TiO₂-NSs) with exposed (001) crystal planes were obtained via a simple one-pot hydrothermal route. And they were utilized to fabricate efficient CdSe quantum dot sensitized solar cells (QDSSCs) for the first time. A power conversion efficiency (PCE) of 5.01% was attained with the TiO₂-NS based cell, which is 63% higher than that of the TiO₂ nanoparticle (TiO₂-NP) based cell under the same conditions. The increased photovoltaic performance mainly profits from more quantum-dot (QD) loading onto TiO₂-NSs due to large pore size and the strong absorption ability with the carboxylate linker of colloidal quantum dots capped using bifunctional linker molecules in the TiO₂-NSs with exposed (001) crystal planes, which lead to an enhancement of light harvesting efficiency and thus significantly enhanced short-circuit photocurrent. Furthermore, the good crystallization, large particle size and low surface area of the TiO₂-NSs also result in fewer defects and provide efficient electron transfer pathways and prolong electron lifetime. Meanwhile, the large pore size of the TiO₂-NS photoanode will also diminish the infiltration resistance of the electrolyte, which is helpful to regenerate the quantum-dots (QDs). The excellent properties of the 2D anatase TiO₂ nanosheet (TiO₂-NS) with exposed (001) crystal planes make it a promising candidate as a photoanode material for highly efficient QDSSCs.