Poly(3-Alkylthiophene)s Via Direct Arylation Polycondensation And Their Photovoltaic Properties

The power conversion efficiency of organic solar cells(OSCs)is increasing year by year,and it is getting closer and closer to the theoretical limit.The high cost of photovoltaic materials has become a bottleneck for its industrial application.The preparation of high-efficiency battery devices based on low-cost polymer photovoltaic materials and non-fullerene acceptor materials has become an international research focus in this field.Poly(3-alkylthiophene)(P3AT)is currently the lowest-cost polymer donor material,but traditional synthesis methods require pre-preparation of thiophene organometallic reagents and produce additional metal by-products.In addition,the relationship between the structural parameters of P3 AT and the performance of the blend system is still unclear,which restricts the further improvement of the performance of P3AT-based solar cells.In this thesis,P3 AT was prepared by direct arylation polycondensation(DAr P),which is environmentally friendly and simple in synthesis steps.Three structural parameters of P3 AT,including molecular weight,regioregularity and side chain length,were regulated.The effects of P3 AT structural parameters on the intermolecular interactions,film microstructure,charge transport,and photovoltaic performance of the blends were studied,aiming to reveal the relationship between structural parameters,donor-acceptor miscibility,aggregated structure of blend films and device performance detailedly.The main results are as follows:1.Adjust the reaction time of direct aryl polycondensation,weight average molecular weight of 8.9-89 kg/mol poly(3-hexylthiophene)(P3HT)were prepared,namely P-9K,P-22 K,P-26 K,P-42 K,P-89 K.It was found that molecular weight has a great influence on the intermolecular interaction between donor and acceptor,which in turn affects the microstructure and photovoltaic performance of the blended films.The P-26K-based blend film has the most moderate miscibility between donor and acceptor molecules,the most ordered molecular packing,and the smoothest surface morphology.Therefore,the P-26K-based blend system achieved an excellent power conversion efficiency of 9.6%.2.Five batches of P3 AT with different side chain lengths were prepared,namely P3 BT,P3PT,P3 HT,P3Hp T and P3 OT.A clear odd-even effect was observed in the P3 AT film: the molecular packing of P3 PT and P3 Hp T tends to face-on stacking,and the molecular packing of P3 BT,P3HT and P3 OT prefers edge-on stacking.The charge transport characterization shows that neat polymer and blend films of P3 PT and P3 HT have good mobility.Combining the two factors of molecular packing and thin-film charge transportation,P3 PT organic solar cell afforded high FF in excess of70% and its PCE reached 9.75%.3.The regioregularity of P3 HT was finely regulated by a mixed ligand strategy,resulting RR-90%,RR-92%,RR-95% and RR-98%.The characterization shows that the regioregularity mainly affects the crystalline equilibrium parameters and the Face-on/Edge-on ratio of the blended films,which in turn affects the bimolecular recombination and photovoltaic performance of the devices.The device performance based on the RR-95%:ZY-4Cl blend system reaches 10.82%,which is the highest value of P3HT-based OSCs to date.In a word,this thesis starts with regulating the three structural parameters of molecular weight,side chain length,and regioregularity,and develops the control methods of structural parameters,and reveals the structure-property relationships between each structural parameter and the morphology and performance of the blend films.The potential of polythiophene prepared by DAr P in the field of organic solar cells are highlighted,which will provide guides for the development of high-performance polythiophene organic solar cells.