Design a novel kind of open-ended carbon sphere for a highly effective counter electrode catalyst in dye-sensitized solar cells

A new kind of carbon sphere (denoted as OCS) with an open end on the surface has been synthesized successfully. The designed OCS shows higher electrocatalytic activity than the conventional solid and hollow carbon sphere (denoted as SCS and HCS) as counter electrode (CE) catalyst for the regeneration of both iodide (I-/1(3)(-)) and sulfide (T-/T-2.) redox shuttles in dye-sensitized solar cells (DSCs). For the iodide electrolyte, the DSCs using SCS, OCS, and HCS CEs yield high power conversion efficiency (PCE) values of 7.8, 8.7, and 8.1%, respectively, indicating the potential to replace expensive Pt CE. Most importantly, the carbon sphere catalysts exhibit obvious advantages when applied in sulfide redox shuttle. The OCS-CE based DSCs produces a high PCE of 6.4%, much higher than that for Pt-CE based DSCs (4.1%). The high catalytic activity of OCS benefits from the sufficient contact between the redox shuttle with the external and internal surfaces of OCS because an open end exists on the surface of OCS, which provide a diffusion channel for the electrolyte into the inner of OCS. This strategy for designing open-ended structure is highly important for the fields of drug delivery, nanodevice, and adsorption, but not confined to catalysis. (C) 2014 Elsevier Ltd. All rights reserved.