The Synthesis And Photovoltaic Performance Of Poly(3-hexylthiophene) Rod-coil Block Copolymer

Polymer solar cell has many advantages, such as lightweight, flexible, low cost,simple process and large area devices.The current researches mainly focus on the designand synthesis of novel conjugated polymer materials. On the basis, it is possible to improvethe photovoltaic device performance and lifetime by optomizing the structure of the deviceand the morphology of the photovoltaic active layer. Through designing different polymermolecules structure, we can regulate the polymer material band gap, control thephotovoltaic active layer morphology and the bulk heterojunction structure. In this way,block copolymer has many potentail advantages in photovoltaic field.This paper mainly studies the synthesis of poly(3-hexylthiophene) rod-coil blockcopolymers and their photovoltaic properties, then illuminates the relationship between thephotovoltaic active layer morphology, microphase separation and the photovoltaicproperties.First, we use the active zinc polymerization to synthetize poly(3-hexylthiophene)(Mn=12338g/mol), which has high regularity, low dispersion (PDI=1.18). Then we modifythe poly(ethylene oxide). On this base, the P3HT-b-PEO copolymer with different blockratios were synthesized by Heck coupling.Next, we study the photovoltaic properties of P3HT-b-PEO block copolymer. Theresults show that the block ratio of P3HT-b-PEO has a great influence on the active layermorphology, microphase separation and the photovoltaic performance.In P3HT/PC61BMsystem, P3HT-b-PEO exists in the interface between P3HT and PC61BM, forming athree-phase ternary system. Introducing P3HT-b-PEO to the photoactive layer has twoadvantages. On the one hand, the P3HT block could self-organize to control theP3HT/PC61BM photoactive layer film morphology and microphase separation; on the other hand, the intrinsic dipole of PEO block could regulate P3HT/PC61BM interfacial energyband arrangement, which can promote the separation of excitons and suppress therecombination of carriers. So the device efficiency improves from3.4%to3.9%whenadding5wt%P3HT-b-PEO5000to P3HT/PC61BM.In summary, this paper designed and synthesized P3HT-b-PEO block copolymers withdifferent molar ratios. By regulating the molar ratio of P3HT-b-PEO copolymer, weobtained excellent photovoltaic active layer film morphology, microphase separationstructure and ultimately improve the photovoltaic device performance.