Synthesis And Photovoltaic Properties Of Novel Conjugated Polymers Containing Dithienopyrrolobenzothiadiazole And Isoindigo

The research progress of the materials and devices of polymer solar cells (PSCs) were summarized systematically. In recent years, PSCs have got more and more attention because they can be made into thin, low cost and large-area flexible devices and possess simple preparation process compared to conventional inorganic solar cells. In this dissertation, several series of donor-acceptor (D-A) conjugated polymers were designed and synthesized to investigate the effects of different acceptors and π-conjugated bridges between donor and acceptor units on absorption spectra, frontier molecular orbital energy levels, charge transport properties and photovoltaic performances. The molecular structures of the as-synthesized compounds were proved and confirmed by1H NMR,13C NMR and mass spectra. The photovoltaic performances of PSCs based on the copolymers were measured. The main results are as follows:1. A novel binary P1and two ternary copolymer P2and P3with DPBT, BDT, DPP units were designed and synthesized. We systematically studied the effects of acceptors and their ratios on optoelectronic properties. The results showed that the optical properties of these copolymers can be easily tune by changing the ratio between DPP and DPBT uints. The spectra became broader with the increase of DPP content in the ternary copolymers, which is favor to increase the Jsc of PSCs based on the copolymers and as a result lead to better photovoltaic performance. At the same time, the polymers have a good solubility and high thermal stability, which is good for the photovoltaic device. Among the three polymers, P3-based PSCs gave the highest power conversion efficiency (PCE) of4.31%(Jx=11.91mA/cm2, Vx=0.69V, FF=0.70).2. A series of novel D-A copolymers PFT-I, PFB-I, and PFTT-I containing isoindigo unit have been designed and synthesized. We systematically studied the effects of electron donor (thiophene, thieno[3,2-b]thiophene and benzo[1,2-b:4.5-b]dithiophene) and π-bridge (furan) on the photophysical, electrochemical properties and photovoltaic performance. The results showed that isoindigo is considered as an strong acceptor uint which is promising for builting D-A copolymer with high Voc. Meanwhile, our results indicated that it was easy to tune the badgap and molecular energy levels of copolymers by copolymerized with different donor units. The power conversion efficiencies (PCEs) of the three polymers are in the range of0.25%-1.46%.