Donor-Acceptor Conjugated Polymers Based On Low Bandgap Materials:Design,Synthesis And Photovoltaic Properties

It is clear that the energy consumption is ever increasing, so harvesting energy directly from sunlight using photovoltaic technology is considered as being one of the most important ways to address growing global energy needs using a renewable resource. Although silicon solar cells cover most of the market of photovoltaics, but there are some drawbacks such as high cost materials, environmental pollution and energy consumption. Polymer solar cells(PSCs) have drawn broad attention in recent years, owing to their advantages of easy fabrication, low cost, light weight, mechanical flexibility and large-area fabrication. In this paper, we synthesize some new kinds of D-A conjugated copolymers as donors and study their properties, such as: optical, electronic properties, thermal properties and photovoltaic properties, and had a preliminary result. The main contents of this paper are described as follows:A facile synthetic strategy toward thieno[3,2-b]indole(TI) derivatives to building D- A conjugated copolymers, we report three polymers based on TI derivatives and DTBT derivatives, P1, P2, P3, these TI based copolymers all have strong and broad absorption ranging from 350?700 nm in solid state. The optimized device based on P3:PC71BM with a relatively higher mobility(2.84×10?5 cm2 V–1 s–1) gave the best photovoltaic performance with a PCE of 2.73%.By Change flexible alkyl chain to C24 branched chain, incorporating TI, BT and thiophene spacers, three conjugated polymers(PTIBT, PTITBT and PTIDTBT) containing N-alkyl-TI as the donor units, 2,1,3-benzodiathiazole(BT) as the acceptor units and thiophene as the spacers were synthesized.The device based on PTITBT:PC71BM(1:3, w/w) shows the best PCE of 5.83%(VOC = 0.69 V, JSC = 13.92 mA cm–2, FF = 61.8%).We can find that the absorption of this kind of material is wide, the band gap is narrow, medium level, there is a better thermal stability. This work provides a feasible strategy for a novel family of TI-based copolymers for high performance PSCs and reports useful insights into a new electron-rich unit for D-A conjugated copolymers.Introduce carbazole into the structure of ladder-type oligo-p-phenylenes, DTBT was chosen as an electron acceptor unit, we synthesize some new kinds of D-A conjugated copolymers as donors and study their properties, such as: optical, electronic properties, thermal properties and photovoltaic properties, and had a preliminary result. Although its efficiency is not high, but the molecular weight of the polymer itself is larger, absorb the wide, good stability, is also a kind of excellent organic semiconductor materials. Optimization of late devices is still in further experiments to explore.