Synthesis And Properties Of Organic Photovoltaic Materials Based On Benzodithiophene And Naphthothiophene Derivatives

Organic solar cells（OSCs）,because of the rich source of raw materials,light weight,low cost,and good compatibility with the roll-to-roll process for making flexible large area thin-film battery components,have been regarded as an important direction of the world’s new energy development and utilization.This paper systematically elaborated the development process in bulk heterojunction organic solar cells,and emphatically summarized the application of benzothiophene-based donor materials for OSCs.Aiming at the shortcomings that the low current carrier mobility and energy conversion efficiency of donor materials for OSCs,this paper introduce the donor materials with the large-planar benzothiophene derivatives,which improves the π-π stacking properties and assembly behavior,leading to better carrier mobility and energy conversion efficiency.Four donor materials were designed and synthesized,we analyze and discuss the relationship between the structure and performance of photovoltaic materials.The research contents are organized as follows:1.A class of donor-acceptor（D-A）narrow band-gap polymers PIDTBDTID and PIDTBDT（ID）2 were designed and synthesized with new molecular design strategy,in which D moieties were employed to construct the main chain and A units were conjugatedly pended onto the D units in the side chain.Where BDT and indacenodithiophene（IDT）groups make up the main chains and one/two isoindigo（ID）moieties are connected to the main chains through a vinyl unit to form the side chains.The optical,electrochemical and photovoltaic properties have been investigated in detail,the PIDTBDTID containing one ID unit exhibited better light-harvesting properties and charge transport properties to lead to better photovoltaic performance with a power conversion efficiency（PCE）of 2.66%,on the other hand,the PIDTBDT（ID）2 with two ID units displayed lower the highest occupied molecular orbital energy levels（HOMO）,an improved VOC of 0.93 V.2.Two novel T-shaped π-conjugated small molecules of DTNT-3DPP and DTNT（DPP-PN）₃ with 4,9-di（thiophen-2-yl）naphtho[2,3-b]thiophene（DTNT）as the donor core and diketopyrrolopyrrole（DPP）as acceptor arms,in the latter case incorporating phenanthrene（PN）units,have been synthesized.It was found that DTNT-3DPP and DTNT（DPP-PN）₃ exhibit better planarity,light-harvesting and charge-transport properties than triphenylamine（TPA）-based star-shaped molecules TPA-3DPP and TPA（DPP-PN）₃,the PCEs of solar cells based on DTNT-3DPP and DTNT（DPP-PN）₃ are 3.47 and 3.69%,respectively.The PCE of the DTNT-3DPP-based OSCs is 1.82 times higher than that of the TPA-3DPP-based OSCs,indicating that the planar DTNT unit can improve the photovoltaic properties of organic small molecules relative to those of the TPA unit.