Preparation of high-efficiency CdS quantum-dot-sensitized solar cells based on ordered TiO2 nanotube arrays

Highly ordered TiO 2 nanotube arrays are synthesized and utilized in preparing front-side illuminated photoelectrodes of CdS quantum-dot-sensitized solar cells (QDSSCs). The CdS quantum dots (QDs) are adsorbed on the ordered TiO 2 nanotube arrays by successive ionic layer adsorption and reaction method (SILAR). Taking the advantages of high surface area and large size of ordered pores of the TiO 2 nanotube arrays, the reaction solutions for SILAR processes can easily penetrate into the photoelectrodes; and the formed CdS QDs can be homogeneously dispersed on the TiO 2 nanotube walls with high coverage. In order to improve photovoltaic performance of QDSSCs, the other important components including counterelectrode, polysulfide (S 2− / S x 2 - ${\mathrm{S}}_x^{2-}$ ) electrolyte, and cycles of SILAR processes for preparing CdS QDs sensitized photoelectrodes are optimized. With thermally treated CuS counterelectrode, pure deionized water based polysulfide (S 2 − / S x 2 - ${\mathrm{S}}_x^{2-}$ ) electrolyte, and 15 cycles of SILAR processes prepared CdS QDs sensitized photoelectrode, the QDSSC can achieve the highest power conversion efficiency about 3.22% under full sunlight illumination (100   mW   cm −2 , AM 1.5G), which is a comparative value among the pure CdS QDs sensitized solar cells.