| 摘要: | 染料敏化太陽能電池(Dye-sensitized solar cells，簡稱DSSCs)因成本低、製作簡易、質輕、多色彩、可製作成可撓曲式…等優點，在新興太陽能電池中具有發展潛力。在染料敏化太陽能電池的組成中，電解質扮演還原染料、傳遞電洞及決定元件之理論開路電壓(Voc)的重要角色。目前最常使用的碘系統電解質因無法藉由結構修飾而調變其氧化還原電位來提高元件之開路電壓，亦無法精準搭配不同HOMO能階的光敏劑。另一方面，鈷錯合物因金屬中心有多重且穩定的氧化態，並且可藉由配位基結構的改變來調控其氧化還原電位，因此具有很大的可行性，成為DSSCs用電解質的研究重點之一。本論文合成出三組鈷錯合物電解質CRC-1、CRC-2、CRC-3。鈷錯合物在450 nm至700 nm間無吸收，不與光敏劑(如：CYC-B11H、SJW-B17、SJW-B18)競爭吸光。CRC-1的氧化還原電位為0.40 V vs. NHE、CRC-2為0.74 V vs. NHE、 CRC-3為0.71 V vs. NHE，皆高於上述光敏劑的HOMO，CRC-2、CRC-3的氧化還原電位較碘系統電解質低，故使用CRC-2及CRC-3電解質之元件有較大的理論開路電壓。以CRC-1電解質搭配染料SJW-B18之元件的開路電壓為0.716 V，由於鈷錯合物電解質易與二氧化鈦上電子進行再結合，所以鈷系統元件之開路電壓略低於碘系統元件的0.749 V。CRC-2電解質可有效提升理論開路電壓，搭配尾端有較大基團的染料SJW-B17可增加TiO2表面覆蓋度，又由於SJW-B17在TiO2薄膜的吸附量較多，以SJW-B17所敏化之元件有高的光電表現：短路電流密度為10.63 mA/cm2、開路電壓為0.916 V、填充因子為0.660 ，光電轉換效率為6.42%。CRC-3電解質有最適當的氧化還原電位0.71 V，與CRC-2電解質比較，對再生染料CYC-B11H、SJW-B17、SJW-B18有較大的驅動力，其中搭配染料SJW-B17所組裝之元件，短路電流密度為13.36 mA/cm2、開路電壓為0.868 V、填充因子為0.619、光電轉換效率為7.19 %。;Dye-sensitized solar cells (DSSCs), is one of the hottest research topics in the new photovoltaic technology, due to its low production cost, simple fabrication process, semi-transparent, light weight, colorful, and can be flexible. In a DSSC device, electrolyte is one of the important components, which reduced the dye, carried the hole to the cathode and determined the theoratical open-circuit voltage (Voc). Iodide/triiodide system is the most commonly used electrolyte, however it’s redox potential can not be tuned to be compatible to sensitizers with various highest occupied molecular orbitals (HOMOs) or increase the Voc of devices by structure modification. On the other hand, cobalt complexes have multiple, reversible oxidation states metal center and their redox potentials can be tuned by the ligands. Therefore ccbalt electrolyte is also one of the important research topics in DSSC. In this study, we synthesis three cobalt-based redox couple coded CRC-1, CRC-2 and CRC-3. CRC-1, CRC-2 and CRC-3 don’t absorb any light from 450 nm to 700 nm, no competing absorption with ruthenium sensitizers (eg: CYC-B11H, SJW-B17 and SJW-B18 developed in our lab). The redox potentials of CRC-1, CRC-2 and CRC-3 are 0.40, 0.74, 0.71 V vs. NHE respectly, all higher than HOMOs of Ru-based sensitizers studied in this thesis. The redox potentials of CRC-2 and CRC-3 are lower than that of iodine-based electrolyte. Devices based on CRC-2 or CRC-3 electrolyte will have higher theoretical Voc. Device using CRC-1 electrolyte and SJW-B18 sensitizer achieves Voc of 0.716 V which is lower than that for the device baesd on iodide/iodine electrolyte, due to the electron in TiO2 recombined with cobalt-based electrolye rapidly. On the other hand, device using CRC-2 electrolyte and SJW-B17 sensitizer has good photovoltaic performance: Jsc: 10.63 mA/cm2, Voc: 0.916 V, FF: 0.660, PCE: 6.42%. CRC-3 electrolyte has a appropriate redox potential for CYC-B11H, SJW-B17 and SJW-B18 dyes due to it has a proper driving force to regenerate the dyes as well as provides high theoretical Voc. Device based SJW-B17 and CRC-3 electrolyte has the best photovoltaic performance amongst the devices studied in this thesis, Jsc: 13.36 mA/cm2, Voc: 0.868 V, FF : 0.619 and PCE : 7.19%. |
