SCIENCE CHINA Physics, Mechanics & Astronomy © Science China Press and Springer-Verlag Berlin Heidelberg 2012 phys.scichina.com www.springerlink.com *Corresponding author (email: wxque@mail.xjtu.edu.cn)  Article  July 2012 Vol.55 No.7: 1158–1162 Special Topic: Nanotechnology for Bio/Energy Applications doi: 10.1007/s11433-012-4785-7 Preparation of hierarchical TiO 2 microspheres for enhancing photocurrent of dye sensitized solar cells JIA QiaoYing 1,2 , QUE WenXiu 1* , QIU XinKu 1 , ZHONG Peng 1 & CHEN Jin 1 1 Electronic Materials Research Laboratory, School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, China; 2 School of Technical Physics, Xidian University, Xi’an 710071, China Received March 23, 2012; accepted May 14, 2012; published online May 28, 2012 Hierarchically structured TiO 2 microspheres were prepared at a low temperature by combining a sol-gel process with a sol- vothermal route and characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. Results indicate that the phase structure of the as-prepared TiO 2 products undergoes a transformation, which changes from amorphous microspheres with a smooth surface in the sol-gel process to hierarchical anatase ones consisting of nano- crystallines after the solvothermal treatment. The hierarchical anatase TiO 2 microsphere shows large surface areas and good light scattering effects as the photoelectrodes for dye sensitized solar cells (DSSCs). DSSCs based on TiO 2 microspheres ex- hibit an improvement power conversion efficiency of 6.58% and a high short current density of 13.83 mA/cm 2 as compared to the commercial P25 based DSSCs with a power conversion efficiency of 4.94% and a high short current density of 10.28 mA/cm 2 . TiO 2 microspheres, photoelectrodes, dye sensitized solar cells PACS number(s): 82.47.Jk, 84.60.Jt, 81.20.Fw, 78.67.Bf, 73.40.Mr Citation: Jia Q Y, Que W X, Qiu X K, et al. Preparation of hierarchical TiO 2 microspheres for enhancing photocurrent of dye sensitized solar cells. Sci China- Phys Mech Astron, 2012, 55: 11581162, doi: 10.1007/s11433-012-4785-7 1 Introduction Dye sensitized solar cells (DSSCs) with low cost and high power conversion efficiency (PCE) have attracted much attention as a promising alternative to silicon based photo- voltaic devices in recent years [1,2]. Many efforts have been made to enhance PCE of DSSCs with various architectures (such as nanoparticles, nanotubes, nanorods/wires, and nanobelts) of wide band gap oxide semiconductor (mainly including TiO 2 and ZnO) photoanodes [3–9]. One approach is to enhance the light harvesting efficiency, which mainly depends on the amount of dye absorption and light scatter- ing effect. In addition, fast electron transport is important for high performance DSSCs. However, for a conventional nanocrystalline photoelectrode with large surface areas and little light scattering, electrons pass through a loosely packed particle network to generate a photocurrent, in- creasing the possibility of interfacial charge recombination losses. Since ordered one-dimensional architectures have proved to be superior in charge transportation and electron lifetime [4,7,10], the performances of the devices are still inferior to those of nanoparticles due to low surface area [7,9,10]. Recently, hierarchical architectures consisting of nanoparticles with different shapes [11–17], such as nanosheets [18], nanoflakes [19], and nanorods [20], have been designed and prepared for special applications due to large surface area and superior charge transportation. Espe- cially, hierarchically porous photoelectrodes were employed