The polymer solar cell is composed of a p-type conjugated polymer donor and a fullerene derivative or a non-fullerene n-type organic semiconductor receptor blending active layer sandwiched between a transparent conductive electrode and a metal electrode. The outstanding advantages of solution processing, light weight, and the ability to be made into flexible and semi-transparent devices have become the focus of research in the global energy field in recent years. Commercial applications of polymer solar cells require high device efficiency, high stability, and low cost , This mainly depends on the development of photovoltaic materials.
Since Alan J. Heeger et al. proposed the concept of bulk heterojunction in 1995, the research on polymer solar cell photovoltaic materials and devices has been continuously developed. In the early stage of the research, the efficiency of the device is very low, and the focus of the research is mainly on improvement. Efficiency, by designing and synthesizing narrowband systems, broad absorption and polymer donor photovoltaic materials with lower HOMO levels, and fullerene derivative acceptor photovoltaic materials with higher LUMO energy levels, to increase the short-circuit current of the device , Open circuit voltage and energy conversion efficiency. In recent years, with the development of narrow-bandgap non-fullerenes n-type organic semiconductor acceptor photovoltaic materials and their absorption of complementary wide band gap polymer donor photovoltaic materials, polymer solar cells Energy conversion efficiency has rapidly increased. Recently, the efficiency of small-area devices in the laboratory has exceeded 12% to 13%, which has reached the threshold of practical application. Therefore, improving stability and reducing costs have become practical applications for polymer solar cells. The key. However, most of the high-efficiency photovoltaic materials that have been reported so far have a complex structure and are difficult to synthesize. It is difficult to meet the needs of commercial applications. Cost-effective photovoltaic materials will be a huge challenge for commercial applications of polymer solar cells.
Under the support of related projects of the National Natural Science Foundation of China and the Chinese Academy of Sciences, researchers from the Chinese Academy of Sciences and the Researcher of the Key Laboratory of the Organic Solids Institute of the Institute of Chemistry, Chinese Academy of Sciences Researcher Li Yongfu recently designed and synthesized a low-cost, high-efficiency polymer donor material PTQ10. (The molecular structure is shown in Figure a). PTQ10 is a simple structure of DA copolymer, in which thiophene ring as a donor unit, quinoxaline as a receptor unit. Alkoxy side chain introduced on quinoxaline in order to improve the polymerization The solubility of the material and enhanced light absorption, the introduction of bifluorine atom substitution to reduce the HOMO level of the polymer and increase the hole mobility. The molecule can be synthesized in two steps by inexpensive raw materials (Figure c) and at the same time achieve close to 90% The total yield makes the cost of the material greatly reduced. More importantly, using the PTQ10 as the donor, the relatively simple structure of the n-type organic semiconductor IDIC (Fig. a) is the polymer solar cell prepared by the receptor (see the device structure The maximum energy conversion efficiency of Figure b) reaches 12.70%, while the efficiency of the reverse-structure device also reaches 12.13% (The efficiency as confirmed by China Institute of Metrology is 12%) At the same time, the device efficiency can exceed 10% with active layer thickness in the range of 100nm to 300nm, which is very favorable for large-area device fabrication. Other high-efficiency polymer donors with efficiency exceeding 10% reported in the current literature Compared with the material, PTQ10 has a very outstanding advantage in terms of productivity and efficiency regardless of the synthesis step (Figure d, e).
Considering the advantages of low cost, high efficiency, and thickness insensitivity, PTQ10 is very promising as a polymer donor material for commercial applications of polymer solar cells. This work was published in Nature-Communications on February 21st (Nat. Commun) . 2018, 9, 743) .
(a) Molecular structure of the donor PTQ10 and the receptor IDIC; (b) Structure diagram of the battery device; (c) Synthesis route of the PTQ10; (d) and (e) Polymer solar cell donor material synthesis steps, yields and Comparison chart of efficiency analysis.
