| Solar energy is a kind of energy that can be directly used by human beings in the process of evolution.Organic solar cells are a device that directly converts solar energy into electrical energy,but there is still much room for improvement in its current photoelectric conversion efficiency.The improvement of the photoelectric conversion efficiency of organic solar cells is inseparable from further research on active layer materials.At present,the research of non-fullerene small molecule acceptor materials is progressing rapidly,but there is still a certain gap between commercialization.The development of new type of acceptor materials is the key to improving the photoelectric conversion efficiency.This dissertation mainly studies receptor small molecule materials,designs and synthesizes asymmetric small molecule receptor materials based on benzothiadiazole derivatives,and studies the relationship between the structure design of these small molecule receptor materials and the efficiency of photovoltaic devices.content include:1.Based on benzothiadiazole,we designed a small asymmetric receptor molecule.Two isomeric small molecule receptors L1 and L2 were synthesized by π bridges linking alkoxy chains at different positions.Using polymer PBDB-T as the donor material,compared with the L1-based device,the open circuit voltage,short-circuit current and fill factor of the L2-based device are significantly improved.By optimizing additives and thermal annealing conditions,the L2-based device finally achieved a higher photoelectric conversion efficiency of 13.08%.This shows that the asymmetric small molecule design strategy is feasible.2.Through the asymmetric small molecule design strategy in the previous work,two new types of small molecules,L3 and L4,were designed.This design is based on the previous work,introducing an octyl chain at the β-position of the intermediate nucleus thiophene unit,and shortening the alkyl chain attached to the intermediate pyrrole to obtain higher photoelectric conversion efficiency.The bridging groups of L3 and L4 are thiophenes with different substituent positions,which are isomers.Based on the efficiency of the L3 photovoltaic device is 9.17%,and its open circuit voltage is0.90 V,this once again illustrates the feasibility of this asymmetric small molecule strategy,and at the same time has a certain effect on the generation of high open circuit voltage.3.By connecting the two intermediates of the benzothiadiazole derivatives in the previous two chapters to the same side chain,small molecule receptors L5 and L6 are designed.The L5 and L6 central units are different,and the π-electron bridge of the alkoxy chain is 3,4-bis(octyloxy)thiophene.The open circuit voltage of L6 is high,and the morphology of the L6 blend film is better,which helps to improve the charge transport performance in the interface layer.After adjusting the ratio of donor to acceptor,the photoelectric conversion efficiency of L6-based device is 14.9%. |
