Zn2SnO4-SnO2 heterojunction nanocomposites for dye-sensitized solar cells

Zn2SnO4-SnO2 heterojunction nanocomposites (ZTO-SnO2) with high mass amount of ZTO were synthesized by a two-step technique. The route involves firstly the synthesis of monodispersed ZnSn(OH)(6) nanocubes with a 50-60 nm edge length as precursors by simple coprecipitation of Na2SnO3 center dot 3H(2)O and ZnCl2 aqueous solution, assisted by ultrasonic treatment and then followed by calcination of the precursors at 800 degrees C under N-2 atmosphere. The as-synthesized nanoparticles were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Heterojunction between ZTO and SnO2 nanoparticle was confirmed by the electron energy loss spectroscopy (EELS) elemental mapping and high-resolution TEM (HRTEM). The photovoltaic performance of the ZTO-SnO2 based DSSC was examined by measuring the J-V curves both in dark and under illumination. The results show that the ZTO-SnO2 based DSSC exhibits superior photovoltaic performance as compared to the single phase ZTO based DSSCs. Under illumination of AM 1.5 simulated sunlight (100 mW/cm(2)), the open circuit voltage of the cell based on ZTO-SnO2 is 706 mV, the short-current density is 2.85 mA/cm(2), and the efficiency is 1.29% which is increased by 43% from 0.90% to 1.29% compared with pure ZTO. The formation of the heterojunctions between ZTO and SnO2 nanoparticles is believed to reduce the recombination between injected electrons and redox I-/I-3(-) and improve the performance of the DSSC. (C) 2010 Elsevier B.V. All rights reserved.