在本研究中，我們在多硫化物電解液中加入硒 (Se) 元素並研發出一種新穎的「多硒硫化物電解液」，藉以提高光電轉換效率 (PCE)，並且利用電化學阻抗分析系統 (EIS) 及時間解析光激螢光 (TRPL) 實驗證實Se加入電解液中能降低光電極/電解液界面中電子與電洞再結合的機會；除此之外，藉由聚乙二醇 (PEG) 或是聚乙烯吡咯烷酮 (PVP) 的加入能夠再有效地降低光電極/電解液界面的電子電洞再結合，使得效率再獲得提升。
　　在過去研究中，無論是光電極與電解液的界面中的電子電洞再結合或是背電極的催化性，都是量子點敏化太陽能電池 (QDSSCs) 中十分重要的議題。在光電極與電解液的界面中，雖然可藉由鈍化層的使用而大幅降低量子點 (QD) 導帶 (或TiO2導帶) 上的電子被電解液的氧化還原對所捕獲，然而，QD導帶上 (或TiO2導帶) 上的電子與QD價帶上的電洞再結合卻難以避免，但在本研究中，我們發現多硒硫化物電解液能夠同時解決光電極/電解液界面及背電極/電解液界面間的問題，故PCE及FF (填充因子) 由7.45%及46.1%分別上升至8.54%及60.0%，均有大幅度地提升；此外，再添加PEG與PVP能夠使得PCE分別再度上升至8.79%及8.61%，這也說明了此新穎的多硒硫化物電解液能夠藉由形成膠態電解液使效率再更上一層樓，凸顯其有潛力能夠形成擬固態電解液 (quasi-solid-state electrolyte) 並應用於QDSSCs的研究中。

The formation of polyselenosulfide ions in traditional polysulfide electrolyte by addition of Se can enhance the power conversion efficiency (PCE) of quantum dot sensitized solar cells (QDSSCs). QDSSCs that employee traditional polysulfide electrolytes suffer from problem of charge recombination at photoanode/electrolyte (PA/electrolyte) interface, which has been reported for years. In this study, to improve PCE, we developed a polyselenosulfide electrolyte based QDSSCs. And we found that charge recombination at PA/electrolyte interface can be effectively reduced in electrochemical impedance spectroscopy (EIS) and time-resolved photoluminescence (TRPL) analysis. To further enhance PCE as well as reduce the charge recombination at PA/electrolyte interface, we added polymer gelators like polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) to polyselenosulfide electrolyte.
Charge recombination in PA/electrolyte interface and catalytic activity of counter electrode (CE) are two important issues which have been discussed in QDSSCs so far. Although the charge recombination from conduction band (CB) of QD (or CB of TiO2) to redox potential of electrolyte can be significantly reduced with passivation layers, however, it is hard to avoid that from CB of QD (or CB of TiO2) to valence band (VB) of QD. Herein, we report the use of polyseneosulfide electrolyte that can solve these two problems simultaneously. As a result, the PCE and fill factor (FF) in our devices has been improved from 7.45% and 46.1% up to 8.54% and 60.0%, respectively. Furthermore, PCE can be further increased to 8.79% and 8.61% by adding PEG and PVP by forming a gel electrolyte, respectively. This indicates that polyselenosulfide electrolyte is also a potential candidate to be quasi-solid-state electrolyte in QDSSCs in the future.

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