探討螢光共振能量轉移效應對三相系統總體異質結構有機太陽能電池之影響

Abstract

在本研究中，我們將實驗室合成出的小分子(SM-4OMe)導入兩成分相系統(PTB7-TH:PC71BM)，成為三相系統有機太陽能電池。將具有互補吸收光範圍的小分子(SM-4OMe)加入兩成分相系統，使太陽能電池元件有更多光吸收範圍作光電轉換；加上小分子(SM-4OMe)與高分子(PTB7-TH)間產生螢光共振能量轉移，讓高分子做光的再吸收，使主動層中產生更多載子，提升整體的短路電流，以提高效率。小分子(SM-4OMe)，與同樣具有BDT(benzodithio-phene)主結構的PTB7-TH做互溶，使三相系統的太陽能電池元件具有很高相容性。當我們適量添加2vol% DIO添加劑於主動層中，將三相材料質量比0.9:0.1:1.5(PTB7-TH:SM-4OMe:PC71BM)，優化元件到10.3%的最高效率。在實驗中，成功以少量添加第三成分的小分子(SM-4OMe)，優化主動層的層狀堆疊方向性，再藉由螢光共振能量轉移，使整體元件光電流(Jsc)和填充因子(FF)上升，進而有效提高太陽能電池光電轉換效率。

In this study, we employed a simple concept of ternary blend system for organic solar cell. Through blending small molecule (SM-4OMe) which has comple-mentary absorption spectrum into the host binary system (PTB7-TH and PC71BM), we successfully broadened the range of absorption spectrum and obtained higher efficiency of harvesting sunlight. We synthesized SM-4OMe with the same benzodithiophene (BDT) unit as the donor of PTB7-TH, which leaded to good morphology compatibility by blending PTB7-TH, SM-4OMe and PC71BM together to form desired packing orientation in the ternary blend films. Moreover, fluorescence resonance energy transfer took place between PTB7-TH and SM-4OMe, generating more carriers to diffuse to the interface of donor and acceptor so that the higher short-circuit current was collected by electrodes and eventually the PCE was optimized. The best PCE of 10.3% was obtained by incorporating PTB7-TH:SM-4OMe:PC71BM at weight ratio 0.9:0.1:1.5 in chlorobenzene, processed with 2vol% 1,8-Diiodooctane (DIO). We only added slight amount of SM-4OMe to form ternary blend films for ensuring the desired packing orientation for the better carrier transport. The result showed the PCE for the single junction organic photovoltaics could be successfully enhanced by a facile ternary blend.