共軛高分子太陽能電池之材料合成與研究

Abstract

本實驗合成兩種新的施體-受體共聚低能隙高分子，pCTDDP與pCbzBtIm，並應用於高分子太陽能電池，希望藉由發展低能隙高分子以增加對光的吸收範圍進而提升高分子太陽能電池的效率。 pCTDDP是以Diketo-Pyrrolo-Pyrrole(DPP)為電子受體，cyclopenta [2,1-b;3,4-b´]-dithiophene(CT)為電子施體。根據UV-Vis吸收光譜，pCTDDP的光學分子能隙為1.31 eV。經電化學分析，pCTDPP的HOMO能階位於-4.95eV，LUMO能階位於-3.31eV，很適合做為高分子太陽能電池的P型材料。將pCTDPP與PCBM以1:3(wt/wt)混掺製成塊狀異質介面高分子太陽能電池，效率可達1%。 pCbzBtIm是以Carbazole為電子施體與我們新合成的電子受體([2,1,5]thiadiazolo [3,4-g] benzimidazole)共聚所得。[2,1,5]thiadiazolo- [3,4-g] benzimidazole為2,1,3-benzothiadiazole(BT)的結構衍生物，是在BT的5,6號位置合成一個imdazole官能基，以加強BT對電子的拉力。高分子pCbzBtIm的光學能隙為1.76 eV，由電化學分析得知pCbzBtIm的HOMO能階位於-5.35 eV，在元件效率上有利於獲得較大的Voc。目前用pCbzBtIm與PCBM以1:4(wt/wt)混掺製成高分子太陽能電池，效率可達1.06%。

Two novel low bandgap polymers, pCTDDP and pCbzBtIm, based on alternating donor-acceptor copolymers have been designed and synthesized for application in polymer solar cells(PSCs). pCTDPP was copolymerized by Diketo-Pyrrolo-Pyrrole(DPP) and cyclopenta[2,1-b;3,4-b´]-dithiophene(CT). According to UV-Vis absorption spectrum, pCTDPP has a relative low bandgap at 1.31 eV. Electrochemical analysis reveal the HOMO level and LUMO level of pCTDDP are on -4.95 eV and -3.31 eV, and is suitable for PSCs. The maximum power conversion efficiency(PCE) of PSCs the based on pCTDPP/PC61BM(1:3, wt/wt) system reaches 1.0% with a short circuit current density(Jsc) of 2.76 mA/cm2, an open circuit voltage (Voc) of 0.6 V, and a fill factor (FF) of 0.60 under AM 1.5G (100 mW/cm2) illumination. We also synthesized a novel copolymer (pCbzBtIm) based on a new acceptor, [2,1,5]thiadiazolo[3,4-g]benzimidazole, and copolymerized with carbazole. pCbzBtIm has a optical bandgap at 1.76 eV, and it’s HOMO level is on -5.46 eV which could get high Voc of polymer solar cells. The maximum power conversion efficiency(PCE) of the PSCs based on pCbzBtIm/PC61BM(1:4, wt/wt) system reaches 1.06% with a short circuit current density (Jsc) of 4.02 mA/cm2, an open circuit voltage (Voc) of 0.76 V, and a fill factor (FF) of 0.34 under AM 1.5G (100 mW/cm2) illumination.