Two star-shaped small molecule donors based on benzodithiophene unit for organic solar cells

Star-shaped small molecules have attracted great attention for organic solar cells(OSCs)because they have three-dimensional charge-transport characteristics,strong light absorption capacities and easily tunable energy levels.Herein,three-and four-armed star-shaped small molecule donors,namely BDT-3 Th and BDT-4 Th,respectively,have been successfully designed and synthesized,which used benzodithiophene(BDT)as the central unit.The two star-shaped intermediates(2 a and 2 b)could be simultaneously obtained by one-step of Suzuki coupling,and 1,2-dimethoxyethane played a key role in the Suzuki coupling.Both of them have excellent thermal stability,good solubility and broad absorption.Four-armed BDT-4 Th shows a slightly higher extinction coefficient,a deeper HOMO energy level and an obviously better phase separation morphology when blended with Y6 than three-armed BDT-3 Th.As a result,increased power conversion efficiency(PCE)of 5.83%is obtained in the BDT-4 Th:Y6-based OSC devices,which is obviously higher than that of the BDT-3 Th:Y6-based devices(PCE=3.78%).To the best of our knowledge,this is the highest PCE among the BDT-based star-shaped donors-based OSCs.This result provides an effective strategy to obtain star-shaped small molecule donor materials for high efficient organic solar cells.

Ethynylene-Linked Oligomers Based on Benzodithiophene:Synthesis and Photoelectric Properties

Two conjugated ethynyl-linked oligomers,oligo(benzodithiophene-ethynylene-benzothiadiazole)(O1)and oligo(benzodithiophene-ethynylene-carbazole)(O2),were synthesized by Sonogashira coupling reaction.Their de-grees of polymerization were 7 and 10,respectively.Their photophysical and electrochemical properties were in-vestigated.O1 exhibitd two strong absorption bands at 404 nm and 483 nm,and O2 at 401 nm and 429 nm.The re-sults of UV-Vis,cyclic voltammetry(CV)and theoretical calculations showed that O1 has a narrower band gap than O2.The conductivities of O1 and O2 were 1.05×10^(−15) and 6.98×10^(−16) S/cm,respectively,and would increase to 1.23×10^(−10) and 1.05×10^(−10) S/cm after doping with iodine.

A simple structure copolymer donor based on carboxylated benzodithiophene for polymer solar cells

The design and development of low-cost and efficient photovoltaic materials remain a major challenge for the research and application of polymer solar cells(PSCs).Therefore,developing efficient photovoltaic polymers with simple structure and easy preparation has become an important research topic.Here we report a facilely synthesized electron-donating polymer X1 with a simple chemical structure,which is composed of carboxylated benzo[1,2-b:4,5-b′]dithiophene(BDT)and thiophene unit.The carboxylate substituents on the BDT unit endowed the polymer with appropriate solubility,low-lying highest occupied molecular orbital(HOMO)energy level,and superior absorption.The PSCs based on X1 as the donor showed a high power conversion efficiency of 16.6%,with a remarkable short-circuit current density of 27.07 m A cm^(-2).These results demonstrated that X1 is a highly promising candidate for low-cost and efficient PSCs.Furthermore,this study revealed the potential of carboxylated BDT as an effective building block in the research and development of high-performance photovoltaic materials.