具交替噻吩與苯環之九環平面梯狀分子於高效能高分子太陽能電池之應用

Abstract

我們成功的設計和合成出具交替噻吩與苯環之九環平面梯狀分子thienyl- phenylene-thienylene-phenylene-thienyl (TPTPT)，其分子結構是利用碳原子將鄰近的噻吩與苯環以共價鍵的方式連結起來，形成含有四個環戊烷之交替噻吩與苯環九環平面梯狀分子。 具有堅硬及平面性之 Br-TPTPT 與不同的電子受體 benzothiadiazole (BT)、quinoxaline (QX)、pyrrolopyrroledione (DPP)、thieno[3,4-b] thiophene (TT)、thienopyrroledione (TPD) 在鈀金屬的催化下進行 Stille Coupling 聚合反應，可成功合成出一系列之隨機型共軛高分子材料 r-PTPTPTQX11、r-PTPTPTQX12、r-PTPTPTTPD11、r-PTPTPTTPD12、r-PTPTPTTT11、r-PTPTPTTT12，隨機型共軛高分子材料的優勢在於可藉由控制電子施體與電子受體比例的不同，來調整分子內電荷轉移的效應，藉此增加光學吸收的強度以達到較理想的吸收特性。 再者，將 Sn-TPTPT 與電子受體 BT、QX、DPP、TT、TPD 反應，可合成出一系列之交替型共軛高分子材料PTPTPTBT、PTPTPTQX、PTPTPTDPP、PTPTPTTPD、PTPTPTTT，交替型共軛高分子材料的優勢則在其結構是由電子施體與電子受體交替而成，在排列上較為規則，也因此會有較好的堆疊，可有效增進電荷遷移率以達較高光電流之特性。 PTPTPTBT 及 PTPTPTQX 因併有堅硬且高平面性之 TPTPT ，並於濕式製程上具有理想的溶解度，且擁有適當的HOMO、LUMO能階及低能隙、高電荷遷移率，致使此兩材料在光電轉換效率上能達到 5.3 % 和 4.2 % 。最為重要的， PTPTPTBT/PC71BM 應用於反結構可達到光電轉換效率 5.9 % ，此研究成果為目前文獻中，低能隙材料應用於反結構中效率最高之材料。

We have successfully designed and synthesized a ladder-type multifused thienyl-phenylene-thienylene-phenylene-thienyl (TPTPT) unit where each thiophene ring is covalently fastened with the adjacent benzene rings by a carbon bridge, forming four cyclopentadiene rings embedded in a nonacyclic structure. The rigid and coplanar Br-TPTPT building block was copolymerized with electron-deficient acceptors, benzothiadiazole (BT), quinoxaline (QX), pyrrolopyrrole-dione (DPP), thieno[3,4-b] thiophene (TT), and thienopyrroledione (TPD) via Stille polymerization. By varying the feed ratio of the monomers, a new class of random copolymers r-PTPTPTQX11, r-PTPTPTQX12, r-PTPTPTTT11, r-PTPTPTTT12, r-PTPTPTTPD11, r-PTPTPTTPD12 with tunable optical and electronic properties were prepared. On the other hand, a series of alternating copolymers PTPTPTBT, PTPTPTQX, PTPTPTDPP, PTPTPTTT, PTPTPTTPD were also prepared by reacting Sn-TPTPT with BT, QX, DPP, TT, TPD acceptors, respectively. PTPTPTBT and PTPTPTQX copolymers incorporating this rigidified and coplanar TPTPT units simultaneously possess excellent solubilities for solution-processability, low bandgaps with suitable position of HOMO/LUMO energy levels, and high hole mobilities, leading to promising PCEs of 4.1% and 5.3%, respectively. Most significantly, the PTPTPTBT/PC71BM-based device with inverted architecture achieved an impressively high PCE of 5.9%. This value represents the highest efficiency ever reported among the inverted solar cells incorporating a D-A type LBG polymer.