Synthesis And Photovoltaic Performance Of Polymer Donor Materials Containing Si Side Chain

In the past few decades,polymer solar cells（PSCs）have achieved breakthrough development due to the tremendous contributions made by scientific researchers in cell structure optimization,device preparation methods,and the continuous upgrading of active layer materials.At present,the energy conversion efficiency（PCE）of single-junction solar cells have surpassed 18%,which is a big step towards practical industrial application.Therefore,in order to solve the massive energy problems needed for sustainable development of mankind,alleviate the lack of fossil energy and the increasingly serious environmental pollution caused by it,and maximize the utilization of solar energy,we should invest more attention to the direction of PSCs.This dissertation mainly explores the impact of polymer donor materials on the photovoltaic performance of PSCs,and designs and synthesizes two series of new ternary conjugated polymer donor materials based on the design strategy of side chain engineering.The main research contents are as follows:（1）Designed and synthesized three new terpolymer donor materials PM10Si,PM20Si and PM30Si,adding 10%,20%and 30%of the benzothiadiazole unit containing siloxane end group side chain into the PM6 main chain structure,respectively.The PSCs are prepared by blending a highly efficient non-fullerene small molecule acceptor（NFA）material Y6,which has an absorption spectrum and a suitable molecular energy level complementary to the terpolymers.The PCE values of devices based on PM10Si,PM20Si,and PM30Si are 12.39%,14.30%and 13.11%,respectively.The active layer of the devices are further optimized by two-step sequential deposition（SD）method.The PM20Si-based devices obtain a high energy conversion efficiency of 15.17%,the current density(J_sc)is 26.92 m A cm^-2,and the fill factor（FF）is 70.44%.These researches show that the high efficiency of PM20Si-based devices is mainly attributed to better phase separation morphology,better molecular orientation and more balanced hole and electron transport in the blend film.（2）Designed and synthesized four copolymer donor materials.The four copolymers with structure of PBT10Si,PBT20Si,PBT30Si and PBDB-Si are obtained by adding 10%,20%,30%and 100%silicyl side chain substituted BDTP units into the D-A copolymer composed of phenyl substituted benzo dithiophene（BDTP）and benzo-[1,2-c;4,5-c’]dithiophene（BDD）,respectively.It is found that PBT20Si:Y6-based blend films exhibite less bimolecular recombination and effective exciton disintegration,and have a relatively high hole mobility（μ_h）value of 4.99×10^-4cm²V^-1s^-1,and a more balanced charge transfer.Ultimately,the PBT20Si:Y6-based devices obtain the highest PCE of 13.06%.These results further indicate that the introduction of silicyl side chains can improve the molecular aggregation and bimolecular recombination of the polymer donor,which is a simple and effective strategy to promote the device performances.