Synthesis of multilayered TiO2 donuts for improved quantum-dot sensitized solar cells

In this paper, a simple method was developed to prepare the submicron-sized multilayered TiO2 donuts (MLTDs), which were constructed by orderly-arranged nanosheets with thickness of similar to 9 nm. Based on the investigation of the time-dependent and other control experiments, a nucleation-assembling-growth mechanism was proposed to describe the formation of the MLTD structure. Then, the MLTDs were introduced into the quantum-dot (CdS/CdSe) sensitized solar cells (QDSSCs) as the photoanode materials. For comparison, QDSSCs based on the randomly assembled nanosheets-based microspheres (RATSs) and commercial P25 nanoparticles were also assembled. Maximum incident photon to charge carrier efficiency (IPCE) value of 57% was observed for CdS/CdSe co-sensitized MLTDs architectures, which was higher than those of RATSs and P25 (50% and 54%, respectively). The enhanced IPCE observed in the MLTDs architectures was mainly attributed to the increased absorption of light. Moreover, the large pore size distribution of MLTDs might be beneficial for electrolyte penetration. Based on these advantages, MLTDs-based QDSSCs demonstrated the highest conversation efficiency of 4.5% in all the three types of QDSSCs. (C) 2014 Published by Elsevier B.V.