The Study On Non-fullerene Solar Cells With High Open Circuit Voltage

Recently,the increasing depletion of non-renewable resources,such as oil and coal,has led to a crucial issue in the development of renewable energy sources which can replace of the fossil energy sources.The polymer solar cells（PSCs）have gradually become a hot issue due to their advantages in safety,clean,simple process,semi-transparency,easy handling of materials and large-area printing technique.This thesis mainly describes the current research status of PSCs,working mechanism,the development on high-open-voltage PSCs,and device engineering.In view of the generally low open circuit voltage(V_oc),this thesis focuses on studying the benzo[1,2-b:4,5-b’]dithiophene（BDT）electron-donating unit based donor-acceptor（D-A）polymer donors for high performance PSCs with high V_ocs.Through using the different BDT-based polymer donors with different electron-deficient units,the PSCs are fabricated for exploring the effect of electron-deficient units on the photovoltaic performance.The specific research content includes the following four parts:（1）The polymers（P1 and P2）are synthesized by copolymerization of BDT donor unit and fluoroalkoxy substituted benzene（FAB）acceptor unit.The effects of introducing F atoms in the para-or ortho-positions on the photophysical,electrochemical properties,theoretical simulation and photovoltaic performance are studied systematically.By optimizing photovoltaic devices,the power conversion efficiencies（PCEs）can be reached to 13%and 15.25%with the V_OCs of 0.83 and 0.87 V,respectively.（2）The polymers（P3 and P4）are copolymerized by BDT donor unit and benzodithiophenoxadiazole（DTBO）acceptor unit.The effects of F atoms substituted in BDT unit on the photophysical,electrochemical properties,theoretical simulation and photovoltaic performance are studied systematically.By optimizing photovoltaic devices,the PCEs of 15.64%and 10.92%with the V_ocs of 0.83 and 0.91 V for P3 and P4 are achieved,respectively.（3）The polymer（P5）is copolymerized by a new fused ring imide（MDTID）acceptor and BDT donor unit.The effect of different electron acceptors on device efficiency has been studied systematically.By optimizing photovoltaic devices,the PCEs are reached to 14.56%and 12.45%with the V_ocs of 0.91 V and 0.95 V for using N3 and IT-4F as electron acceptors,respectively.（4）The polymers（P6 and P7）are copolymerized by BDT donor unit and two new five-membered fused-ring dilactone（BL）acceptor units.The effect of different five-membered fused-ring dilactone（BL）units on the photophysical,electrochemical properties,theoretical simulation and photovoltaic performance has been studied systematically.By matching with a high-LUMO acceptor of IT-4F,the PCEs are reached to 7.31%and 10.44%with the very high V_ocs of 0.94 and 0.96 V for P6 and P7,respectively.