新型共軛分子之合成與鑑定及其蒸鍍型太陽能電池之應用

Abstract

對於能源無盡的需求，伴隨著日益加速的全球暖化，使得再生能源的開發刻不容緩。取之不盡的太陽光，無疑是最環保的能量來源，而光伏打科技則是將光能轉換成電能最直接的方式。相較於市場上主流的矽基太陽能電池，有機太陽能電池因具有成本低、重量輕、可撓曲，以及生產過程中對環境衝擊較低等優勢，日漸備受重視。而其中極具關鍵的活化層材料，相較於聚合物而言，若採用小分子，因其為組成單一的純物質，各批次之間，物化性質的再現性高，又因分子量小，故還能藉由蒸鍍的方式精密地調控材層的模厚、濃度與範圍以製備成元件，且製程與現有的OLED面板機台相容性高，因此深具商業化的潛力。 本論文研究主軸即為蒸鍍型D-A-A結構之小分子電子予體材料的開發，志於利用分子設計調控有機太陽能材料的光電特性進而提升元件效率。第一章簡介利用分子設計調控有機材料能隙的策略與最近期的高效率實例，第二章則引入平面性的推電子基團，利用共軛效應，合成出開路電壓高達1 V的NTU-1材料。第三章探討在拉電子基團上修飾氟與氯原子的效應，並利用氟原子與氯原子特有的引導效應，合成出光電轉換效率高達9.2%的PFo材料。最後則是合成出同時結合共軛效應與引導效應於一身的iBuBTDC-Fo材料，光電轉換效率達8.5%，其開路電壓達0.98 V，具應用於串聯式電池的潛力。以上的研究成果期能作為未來分子設計方向的指標與啟發。

Organic solar cells have attracted great attention recently because of their advantages such as low cost, light weight, and flexibility. Particularly, the small molecule-based materials prevail over the polymeric alternatives with the merits of well-defined molecular structure, easier purification, better batch-to-batch reproducibility, and higher compatibility with precise vacuum-processed device fabrication. In this research, we endeavored to investigate the molecular structure-optoelectronic property-device performance correlations by synthesis and characterization of four series of donor-acceptor-acceptor-configured (D-A-A) electron donor materials based on the modifications of molecular structure from the electron donating unit (D) to the accepting unit (A). We firstly incorporated the fused-heterocyclic thienoindole as the donating unit for its conjugate effect, which lowers the frontier orbitals of the NTU pair, facilitates the quinoid and ICT character of the regioisomeric NTU-2, giving it a benign efficiency of 5.2%, and provides NTU-1 a Voc larger than 1 V. Later, we introduced the highly electronegative fluorine atom to the different substitution positions of benzothiadiazole accepting unit for its inductive effect that effectively lowered HOMOs, therefore enhancing the Vocs to 0.94 V, among which PFo strikes a PCE of 9.2%. Finally, we integrated the inductive effect with the conjugate effect by incorporating the fluorinated as well as the chlorinated benzothiadiazole accepting unit with the fused-heterocyclic donating unit to retain the Jsc while enhancing the Voc. By taking both the advantages, iBuBTDC-Fo achieved a PCE of 8.5% with Voc of 0.98 V. These results realized the establishment of the structure-property-performance relationship as a guideline for further efficiency enhancement.