N,N-二甲基碘化铵:染料敏化太阳能电池钙钛矿前驱体电解质的高效添加剂

Dimethylammonium Iodide: Boosting Photocurrent for Dye-sensitized Solar Cells with Perovskite Precursors Electrolyte

钙钛矿前驱体(PbI2和CH3NH3I)分散体系,作为一种新型染料敏化太阳能电池(Dye-sensitized Solar Cells,DSSCs)电解质,光电流和光电压的继续提升是其发展过程中亟待解决的问题.在本工作中,研究发现,通过引入二甲基碘化铵(DMAI)作为钙钛矿前驱体电解质的高效添加剂,可将光电流密度从12.85 mA·cm-2急剧提升至19.19 mA· cm-2.借助阻抗和塔菲尔曲线分析,发现其光电流的增加与TiO2半导体导带的向上移动对不平衡载流子复合的抑制作用具有一定的相关性.进一步通过叔丁基吡啶的调节作用,可将光电转换效率提高到8.46%,超过了传统的碘电解质.也为染料敏化太阳能电池的研究开辟了新的途径.

As a typical representative of the third-generation solar cell, the dye-sensitized solar cells (DSSCs) with iodine electrolyte have attracted much attention due to its low fabrication cost, simple assembly process and relatively high photoelectric conversion efficiency (PCE). However, all studies about electrolytes are essentially related to redox couples of iodine, cobalt and copper with different chemical valences by far. Based on above systems, it is difficult to continually enhance the photocurrent of DSSCs due to the energy level tunability limitation between the redox potential and the dye regeneration. However, the study of perovskite precursor (PbI2 and CH3NH3I) as dye-sensitized solar cell electrolyte has just started, and its specific mechanism is still unclear. As the newly-presented electrolyte of dye-sensitized solar cells, its development bottleneck of photocurrent and photovoltage is an urgent issue to be solved. Herein, dimethylammonium iodide (DMAI) was introduced as a high-efficiency additive for the perovskite precursors electrolyte and the photocurrent is sharply increased from 12.85 mA·cm-2 to 19.19 mA·cm-2. The electron transfer process was preliminary studied in this system via chemical capacitance, electron lifetime, charge transfer impedance, and Tafel curve. The Tafel curve test is based on the dummy cell with Pt|electrolyte|Pt device structure, and the others on the completed cells. In particular, the results of chemical capacitance show that the addition of DMAI obviously leads to the upward shift of the TiO2 conduction band. It is found that the increase in photocurrent is attributed to the inhibition of the electron recombination caused by unbalanced carriers due to the upward shift of the TiO2 semiconductor conduction band. By the modulation action of tert-butylpyridine (TBP), the photoelectric conversion efficiency was increased to 8.46% over the iodine system. It lays a solid foundation for the expansion of the dye-sensitized solar cell electrolyte system, the sustainable improvement of its performance and future application.