Reducing Energy Loss and Morphology Optimization Manipulated by Molecular Geometry Engineering for Hetero-junction Organic Solar Cells

of main observation and conclusion Molecular geometry engineering is an efective strategy to control the micromorphology and molecularenergy level in organic photovoltaics(OPVs).Two novel copolymers based on alkysilyl-and chloride-functionalied benzodithiophene(BDT)were designed and synthesized for wide bandgap copolymer donor materials in OPVs.It was found that the two copolymers exhited distinctly different proper-ties in active layer when blended with fulerene-fre acceptor T-4.The chloride-functionalited copolymer PBDTCI-TZ2 with deeper molecular energy leveland better coplanar structure induced more ordered aggregation in blend flm.Thus,the device based on PBDTC-TZ exhibits better energy alinmentwith IT-4F and smallr radiative recombination.furthermore,the non-radiative recombination of PBDTCI-TZ.T-4F based device is about 45 mV lowerthan the PBDTS-TZ/T-4F based device,contributing to a lower enery loss(Ein,and a higher open-cicut voltage(Vc).As a resut,the devices based onthe blend of PBDTC-TZ2.IT-4F exhibit a high power conversion efficiency(PCE)of up to 12.2%with a high Vvoe of 0.837 Vv,higher than that of PBDTSi-TZ:IT-4F,of which the PCE is 11.2%with a Voc of 0.781V.