本論文以缺電子片段thienothiadiazole為結構主體合成出六個小分子，作為有機光伏打電池的光敏材料，其中兩個為對稱結構，另外四個分子為不對稱結構，此六個分子的薄膜紫外-可見光吸收範圍均超過1000 nm。為方便做成BHJ元件，中心主體的thienyl基團修飾上長碳鍊以增加溶解度；對稱結構分子以dicyanovinyl或是octyl cyanoacryl作為拉電子基，其HOMO與LUMO能階很低，類似於PCBM，將其與P3HT混摻所製成之元件呈現較低的短路電流，可能由於載子移動速率非常不平均而導致。而不對稱分子分別以carbazole或是bithiophene為推電子基，dicyanovinyl或octyl cyanoacryl作為拉電子基，所組合出的四個分子，其HOMO與LUMO能階顯示適合作為電子予體，將其與PCBM混摻製成元件，元件的光電轉換效率範圍為0.22?0.54%，由於光電流表現不佳，導致元件效率也沒有很出色，其原因除了電洞傳遞速度不夠快以外，可能促使電子?-電洞對分離的能量也不足的緣故。雖然thio-CN的單光轉換效率不高，但其EQE分布範圍包含可見光與近紅外光區，可望作為二元系統(binary)之添加光敏染料，補充原染料層於近紅外光區的吸收值，而增加EQE的單光轉換範圍。 Six molecules containing an electron deficient thienothiadiazole entity in the conjugated segments have been synthesized for organic photovoltaic solar cells. Two of the compounds have a symmetrical structure with electron accepting dicyanovinyl or octyl cyanoacryl group at the peripheries. The strong electron withdrawing nature renders the two molecules to have deep HOMO and LUMO levels, which are suitable to be used as the n-type materials of OPV. BHJ solar cells were fabricated from the blend of the molecules with P3HT, however, the cell performance was poor because of low short-circuit currents. The low efficiency may be attributed to the imbalance of the carrier mobilities. The other four molecules contain electron donating carbazole or bithiophene at one perphery, and electron accepting dicyanovinyl or octyl cyanoacryl group at the other perphery. BHJ solar cells fabricated from the blend of the molecules with PCBM have efficiencies ranging from 0.22 to 0.54%. The low photocurrents, possibly stemmed from the low mobility of holes, or insufficient driving force for charge separation because of small enengy difference of the LUMO between the compound and PCBM, result in low efficiencies of cells. Though thio-CN has low short-circuit currents because of the low value of EQE, its EQE plot covers visible and near-IR spectral regions. These molecules may be used as the additives of binary organic solar cells for better light harvesting due to their NIR-absorbing characteristic.
