氧气氛烧结电极对染料敏化太阳电池微观性能影响机理研究

Influence of O_2 Annealed Electrode on Microcosmic Performances in Dye-sensitized Solar Cells

为了改善染料敏化太阳电池内电子的传输复合过程,研究者尝试不同方法制备或改性TiO2薄膜.不同烧结气氛可以改变TiO2薄膜的表面特性,是一种有效的方法并被广泛研究.采用两步烧结法制备氧气氛烧结TiO2电极并应用于染料敏化太阳电池:第一步将电极在空气或氧气氛中510℃保温30 min以清除TiO2薄膜中有机物;第二步将电极进一步在氮气氛中510℃保温10 min以移除电极表面吸附的多余氧原子.通过与空气烧结电池宏观性能及微观性能的对比,细致研究了氧气氛烧结电极表面特性对染料敏化太阳电池传输复合微观动力学过程的影响机制.TiO2薄膜表面特性及带边移动、电子传输复合过程的表征分别借助XPS能谱仪和强度调制光电流谱(IMPS)/强度调制光电压谱(IMVS)等探测技术完成.结果表明,氧气烧结电极Ti3+复合中心减少,使电池内部电子复合得到有效抑制.同时,氧气烧结电极染料吸附量增加且导带边正移,使得光生电子浓度升高,膜内电子传输过程加快.最终,氧气烧结电极有效改善了电池光吸收效率、电子收集效率以及注入效率,使电池效率由6.90%提升至7.53%.

Over the last decade, different techniques had been employed to prepare nanoporous TiO2 electrode, aiming to improve the electron transport and depress electron recombination processes in dye-sensitized solar cells （DSCs）. Preparing TiO2 films by various atmospheres and annealing processes was an effective method to change their surface properties. Many results had been published recently regarding the effect of annealing atmospheres on cell performances, but there is no de- tailed study disclosing the working mechanism of O2 annealed electrode so far. In the present work, the influence of 02 an- neal electrode on charge transport and recombination processes in dye-sensitized solar cells （DSCs） was investigated. TiO2 films were prepared by a two-step annealing process. The 1 st-step of annealing was performed in air or oxygen at 510 ~C for 30 rain which effectively removed the residual organics originated from the TiO2 precursor pastes. The 2nd-step of annealing was performed in nitrogen at 510 ~C for 10 min which removed extra oxygen atoms resulted from the incorporation of oxy- gen atoms adsorbed onto photoanode surface during the 1 st-step of annealing. Series resistance and fill factor （FF） of the cell can be improved by the 2nd-step. The surface properties of siutering films were characterized by X-ray photoelectron spec- troscopy analysis （XPS）. The microcosmic processes of recombination, transport and band edge movement were detected by intensity-modulated photocurrent spectroscopy （IMPS）/intensity-modulated photovoltage spectroscopy （IMVS）. It was found that both open-circuit photovoltage （Voc） and short-circuit photocurrent （Jsc） were improved by O2 annealed electrode. 02 anneal could reduce the recombination centers of Ti3＋ defects and the recombination between electron and 13 was conse- quently depressed. Additionally, the electron transport process in TiO2 films was also improved due to the increase of dye absorption amount and more positive band shift by 02 anneal. Overall, 02 annealed electrode enhanced the light absorption efficiency, electron collection efficiency and injection efficiency, inducin~ the cell efficiency rose from 6.90% to 7.53%.