Neale Nathan R, Kopidakis Nikos, van de Lagemaat Jao, Grätzel Michael, Frank Arthur J
National Renewable Energy Laboratory, Golden, Colorado 80401-3393, USA.
J Phys Chem B. 2005 Dec 15;109(49):23183-9. doi: 10.1021/jp0538666.
The mechanism by which the adsorbent chenodeoxycholate, cografted with a sensitizer onto TiO2 nanocrystals, alters the open-circuit photovoltage and short-circuit current of dye-sensitized solar cells was investigated. The influence of tetrabutylammonium chenodeoxycholate on dye loading was studied under a variety of conditions in which the TiO2 films were exposed to the sensitizing dye and coadsorbent. Photocurrent--voltage measurements combined with desorption studies revealed that adding chenodeoxycholate reduces the dye loading by as much as 60% while having a relatively small effect on the short-circuit photocurrent. Calculations along with measurements showed that even at low loading, enough dye is present to absorb a significant fraction of the incident light in the visible spectrum. In concurrence with the observations of others, we find evidence for weakly and strongly adsorbed forms of the dye resulting from either different binding conformations or aggregates. The most strongly adsorbed dyes are less susceptible to displacement by chenodeoxycholate than those that are weakly adsorbed. While having no observable effect on dye coverage, multiple exposures of a TiO2 film to a dye solution substantially increased the fraction of strongly adsorbed dye as judged by the resistance of the adsorbed dye to displacement by chenodeoxycholate. Measurements of the open-circuit voltage as a function of the photocharge density, determined by infrared transmittance, showed that chenodeoxycholate not only shifts the conduction band edge to negative potentials, but also significantly increases the rate of recombination. The net effect of adding chenodeoxycholate is, however, to improve the photovoltage.
研究了与敏化剂共接枝到二氧化钛纳米晶体上的吸附剂鹅去氧胆酸盐改变染料敏化太阳能电池开路光电压和短路电流的机制。在各种条件下，研究了四丁基铵鹅去氧胆酸盐对染料负载量的影响，其中二氧化钛薄膜暴露于敏化染料和共吸附剂中。光电流-电压测量与解吸研究相结合表明，添加鹅去氧胆酸盐可使染料负载量降低多达60%，而对短路光电流的影响相对较小。计算结果与测量结果表明，即使在低负载量下，也存在足够的染料来吸收可见光谱中相当一部分的入射光。与其他人的观察结果一致，我们发现了由于不同的结合构象或聚集体而导致的染料弱吸附和强吸附形式的证据。与弱吸附的染料相比，吸附最强的染料更不易被鹅去氧胆酸盐取代。虽然对染料覆盖率没有明显影响，但通过二氧化钛薄膜多次暴露于染料溶液中，根据吸附染料对鹅去氧胆酸盐取代的抗性判断，大大增加了强吸附染料的比例。通过红外透射率测定的开路电压作为光电荷密度的函数的测量结果表明，鹅去氧胆酸盐不仅将导带边缘移向负电位，并显著增加复合率。然而，添加鹅去氧胆酸盐的净效果是提高光电压。
