Organic Conjugated Semiconductors For Oragnic Solar Cells And Photocatalytic Hydrogen Evolution

Nowadays energy shortage and environmental pollution are major problems for the development of the world for the future.The large-scale usage of clean and renewable energy,such as solar energy,hydrogen energy has a great potential and opportunity to solve the dilemma.Developing new technology and getting an easy access to use renewable energy are the responsibilities and obligations for scientists currently.Solar energy is a kind of inexhaustible energy,and hydrogen energy has the characteristics of high calorific value and no pollution,which are of great development potential.Since the1990s,many researchers have devoted themselves to the research of organic solar cells and photocatalytic hydrogen evolution.Organic solar cells have the characteristics of light weight,flexibility,solution processing,and large-scale production,and can directly convert solar energy into electric energy.Since2015,the research of non-fullerene acceptor materials has lead the development of the organic solar cells to an unprecedented height.In 2020,the energy conversion efficiency of organic/polymer materials-based organic photovoltaic devices has exceeded 18%.On the other hand,photocatalytic hydrogen evolution can convert solar energy to hydrogen energy directly,which has unique advantages in the development of hydrogen energy.The development of photocatalysts with high catalytic activity and high stability is an urgent problem in the field of hydrogen production evolution.Organic conjugated materials have attracted much attention due to their various chemical structures and their performance can be controlled easily.This dissertation focuses on the research organic solar cells and hydrogen energy.By controlling of the chemical structure,energy level and aggregation state of organic conjugated molecules,the relationship between the structure and properties of materials was explored and the materials were successfully applied to organic solar cells and photocatalytic hydrogen evolution,the internal mechanism was also discussed.In the second chapter,we prepared a series of small molecules（BTIC-OEG-Cl,γ-γBTIC-OEG-Br,β-γBTIC-OEG-Br andβ-βBTIC-OEG-Br）,in which three small molecules are isomers.Through chemical characterization,we determined their chemical structures and explored the relationship between molecular structures and optical/electrochemical properties.We applied four kinds of materials to organic solar cells,and optimized photovoltaic devices.The results show that BTIC-OEG-Cl has a more red-shifted absorption spectrum,more efficient charge separation and higher carrier mobility,which leads to the highest power conversion efficiency（13.46%）.Furthermore,we were surprised to find that the four kinds of small molecules showed excellent catalytic activity in photocatalytic hydrogen evolution,and the highest hydrogen evolution rate was 36.45 mmol g^-1h^-1.In the third chapter,we have successfully constructed a new multi-component photocatalytic hydrogen evolution system based on electron donor/electron acceptor materials.Four kinds of small molecular materials,IDT-4-Roh,IDTT-4-Roh,IDT-4-Roh-CN and IDTT-4-Roh-CN,were synthesized and applied to photocatalytic hydrogen evolution by matching with a polymer P4EOBDT-TTE.Among them,the multi-component system of IDT-4-Roh:P4EOBDT-TTE=95:5 showed the highest catalytic hydrogen evolution rate at about44.98 mmol g^-1 h^-1.Furthermore,we explored the reasons for the difference of photocatalytic hydrogen evolution efficiency by testing the response photocurrent,EIS,and Photoluminescence of single/multi-component system,explaining the deeper mechanism of multi-component system.In the fourth chapter,we designed and synthesized four kinds of conjugated polyelectrolytes as photocatalysts for hydrogen evolution.We introduced quaternary ammonium salt group into the side chain of polymers,which effectively improved the hydrophilicity of the molecule.We found that the structure of porphyrin coordinated by different metal atoms had a significant effect on the photocatalytic performance of hydrogen production.Among them,PPF-Pt-Br could significantly improve the photocatalytic hydrogen production efficiency,up to 37.9 mmol g^-1 h^-1.The high catalytic activity of PPF-Pt-Br can be attributed to its high exciton generation efficiency,lower charge transfer resistance,stronger interaction with water molecules and cocatalyst.In the fifth chapter,we aimed to broaden the absorption spectrum of the materials to improve the photocatalytic hydrogen production reaction.We synthesized two polymer materials PPDPP-Zn and PPDPP-Cu.By introducing DPP copolymerization unit into the polymer,the polymer had wide absorption and made full use of visible light energy;By introducing the alkyne bond into both sides of the porphyrin molecule,the steric hindrance effect between the copolymerization units was effectively reduced,and the structural units of the polymer are smoother.We used F127 as a surfactant to prepare the microcell of polymer materials,which can be stably dispersed in water.The hydrogen production efficiency of PPDPP-Zn reached to 2.67 mmol g^-1 h^-1.