Tae Eunju Lee, Lee Seung Hwan, Lee Jae Kwan, Yoo Su San, Kang Eun Ju, Yoon Kyung Byung
Center for Microcrystal Assembly, Department of Chemistry, and Program of Integrated Biotechnology, Sogang University, Seoul 121-742, Korea.
J Phys Chem B. 2005 Dec 1;109(47):22513-22. doi: 10.1021/jp0537411.
Dye-sensitized nanoporous TiO2 solar cells (DSSCs) can be classified into two types, namely, Type-I and Type-II. Type-I DSSCs are the DSSCs in which electrons are injected from the adsorbed dyes by photoexcitation of the dyes followed by electron injection from the excited dyes to TiO2 (pathway A). Type-II DSSCs are the DSSCs in which electrons are injected not only by pathway A but also by direct one-step electron injection from the dyes to TiO2 by photoexcitation of the dye-to-TiO2 charge-transfer (DTCT) bands (pathway B). The DSSCs employing catechol (Cat) or its derivatives as the sensitizers have been the typical examples of Type-II DSSCs. However, their solar energy-to-electricity conversion efficiencies (eta) have never exceeded 0.7%, and the external quantum efficiencies (EQE) at the absorption maximums of the DTCT bands have never exceeded 10%. We found that the attachment of electron-donating compounds such as (pyridin-4-yl)vinyl and (quinolin-4-yl)vinyl, respectively, to Cat (designated as Cat-v-P and Cat-v-Q, respectively) leads to 2- and 2.7-fold increases, respectively, in eta, driven by large increases in short circuit current (Jsc). The EQE increased from 8.5 to 30% at 400 nm upon changing from Cat to Cat-v-P, at which only the DTCT band absorbs. In the case of the Cat-v-Q-sensitized DSSC, even the eta obtained by exciting only the DTCT band was higher than 1%. Interestingly, the illumination of only the DTCT band resulted in the increase of fill factor from 62.6% to 72.3%. This paper provides for the first time an insight into the strategy to increase the eta values of Type-II DSSCs.
染料敏化纳米多孔二氧化钛太阳能电池（DSSC）可分为两类，即I型和II型。I型DSSC是通过染料的光激发从吸附的染料中注入电子，随后从激发态染料向二氧化钛注入电子的DSSC（途径A）。II型DSSC是不仅通过途径A注入电子，还通过染料 - 二氧化钛电荷转移（DTCT）带的光激发从染料直接一步注入电子到二氧化钛的DSSC（途径B）。采用儿茶酚（Cat）或其衍生物作为敏化剂的DSSC是II型DSSC的典型例子。然而，它们的太阳能到电能的转换效率（η）从未超过0.7%，并且DTCT带吸收最大值处的外量子效率（EQE）从未超过10%。我们发现，分别将给电子化合物如（吡啶 - 4 - 基）乙烯基和（喹啉 - 4 - 基）乙烯基连接到Cat上（分别指定为Cat - v - P和Cat - v - Q），由于短路电流（Jsc）的大幅增加，分别导致η提高了2倍和2.7倍。从Cat变为Cat - v - P时，400 nm处的EQE从8.5%增加到30%，此时只有DTCT带吸收。在Cat - v - Q敏化的DSSC情况下，即使仅通过激发DTCT带获得的η也高于1%。有趣的是，仅照射DTCT带导致填充因子从62.6%增加到72.3%。本文首次深入探讨了提高II型DSSC的η值的策略。
