Superior energy band structure and retarded charge recombination for Anatase N, B codoped nano-crystalline TiO2 anodes in dye-sensitized solar cells

Abstract

This work reports the preparation of N, B codoped TiO₂ (N, B–TiO₂) electrodes in dye-sensitized solar cells (DSCs) by a facial modified sol–gel method. After the nitrogen and boron dopants incorporated into the TiO₂ electrodes, the cubic-like TiO₂ nanocrystallites with diameters of 22∼24 nm were obtained efficiently. The back electron transfer of the DSC based on the N, B–TiO₂ electrode was studied by measuring the electrochemistry impedance spectra (EIS) and the EIS for the DSCs showed that the enhanced electron lifetime for the dye-sensitized B, N–TiO₂ solar cells could be attributed to the formation of an O–Ti–B–N bond in the TiO₂ photoelectrode, which retards electron recombination at the dyed N, B–TiO₂ photoelectrode/electrolyte interface after N, B codoping as compared to the undoped DSC. We found that a high efficiency of 8.4% for the DSC (active area:4 cm²) based on the N, B–TiO₂ anode under 0.2 sun illumination was received. In particular, the photovoltaic performance of the DSC under high temperature conditions (60 °C) and one-sun light soaking over a time of more than 1100 h showed that the DSC based on the N, B–TiO₂ electrode exhibited a better stability compared to the undoped DSC. The excellent photoelectrochemical performance could be attributed to the ideal combination of retarded electron recombination and superior energy band structure from the unique N, B–TiO₂ particle structure.