天然染料共敏化太阳能电池中共吸附剂的研究

Co-Adsorbent in Natural Dye Co-Sensitized Solar Cells

采用紫外-可见吸收光谱对花青素、β-胡萝卜素、2种染料混合共敏以及添加了共吸附剂脱氧胆酸(DCA)的混合共敏4种染料体系进行光谱吸收性能测试,发现混合共敏体系能有效地拓展光谱吸收范围,实现300~600 nm之间的全谱吸收,明显提高了电池的光伏性能;在此基础上对4种染料溶液进行电化学测试分析,发现共吸附剂分子不仅可以降低染料的团聚,同时还有助于调节染料的能级位置,使其与Ti O2光阳极的能级位置和电解液的氧化还原电位更加匹配。相应地,DCA的加入减小了染料的LUMO与Ti O2导带的能级差值,即降低了电子注入驱动力(从0.92 e V降低到0.81 e V),从而降低了能量损失;同时,DCA增加了染料的HOMO与电解质的氧化还原电势的差值,使得混合染料的再生驱动力从0.24 e V达到0.35 e V,保证了染料的再生效率,明显提高了电池的短路电流密度,增幅达到约22%,相应地开路电压提高了约33 m V,光电转换效率提高了30%以上,达到0.292%。

The optical properties of four different kinds of dye solution including anthocyanin, β-carotene, their mixture and the mixture with co-adsorbent of deoxycholic acid(DCA) were measured by UV-Vis absorption spectroscopy. It is found that co-sensitization between anthocyanin and β-carotene enables the absorption in the whole range of 300~600 nm, revealing that co-sensitization is an effective approach to enhance the light absorption properties. Correspondingly, the photovoltaic performances are significantly improved after co-sensitization compared to those sensitized by only one kind of dye molecules. Based on this, electrochemical analysis was conducted, which demonstrates that DCA is an effective co-adsorbent in the present dye system since the dye aggregation is hindered and the energy level of the dye mixture is altered. Both the HOMO and LUMO are tuned to match the energy level of TiO_2 better. In detail, DCA decreases the difference between the LUMO of dye mixture and the conduction band of TiO_2, namely the electron injection driving force from 0.92 to 0.81 eV, thus decreasing the energy losses. Meanwhile, DCA increases the difference between the HOMO of the dye mixture and the redox potential of the electrolyte, for which the regeneration driving force of dye molecules is enlarged from 0.24 to 0.35 eV leading to efficient dye regenerations. As a result, the addition of DCA in co-sensitized dye solutions has increased the short-circuit current by about 22%, and the open-circuit voltage is improved by 33 m V. Overall, the efficiency is enhanced by more than 30%, reaching up to 0.292%.