The Design,Synthesis And Characterization Of High-performance Wide-bandgap Polymer Donor Materials For Polymer Solar Cells

Polymer solar cells?PSCs?have attracted much attention due to their potentials for making large area and flexible modules through solution processing.The power conversion efficiency?PCE?of PSCs is relatively low,which restricts their further development.In this paper,to improve the performance of PSCs,we mainly focused on wide-bandgap polymer donor materials based on thiazole as the acceptor unit and discussed the relationship between the molecular structures of polymers,blend morphology in the active layer,and the photovoltaic performance.The main results are as follows:1.A wide-bandgap conjugated polymer PTZ1 based on thienyl substituted benzodithiophene as donor unit and thiazolothiazole as acceptor unit was designed and synthesized.The polymer exhibited a broad bandgap of 1.97 eV,a deep HOMO energy level of-5.31 eV and a relatively high hole mobility of 3.86×10^-3 cm² V^-1 s^-1.Single junction PSCs based on PTZ1:PC₇₁BM?1:1.25,w/w?showed a PCE of 7.7%with a V_oc of0.95V under the illumination of AM 1.5 G,100 mW cm^-2.The tandem PSCs based on PTZ1 as donor material in the front cell exhibited a high PCE of 10.3%.2.A wide-bandgap conjugated polymer PTZ6 based on alkoxylphenyl substituted benzodithiophene as donor unit and bithiazole as acceptor unit was designed and synthesized.The polymer exhibited a wide bandgap of 2.0 eV,a low-lying HOMO energy level of-5.36 eV and a hole mobility of 1.29×10^-3 cm² V^-1 s^-1.The PSCs based on PTZ6:PC₇₁BM?1:1,w/w?showed a PCE of 8.1%with a high FF of 76.7%under the illumination of AM 1.5 G,100 mW cm^-2.Moreover,for this blend system,the photovoltaic performance of the devices changes little when the active layer thickness increases from 90nm to 220 nm.More importantly,non-fullerene PSCs based on PTZ6:ITIC?1:1,w/w?exhibited a PCE of 10.3%with a high V_oc of 1.01 V and a low E_loss of 0.58 eV.