The organic solar cell is composed of a p-type organic semiconductor donor and an n-type organic semiconductor (n-OS) acceptor blending active layer sandwiched between a transparent conductive electrode and a metal electrode, and has a simple structure, light weight and low cost. And the advantages of using solution processing methods to prepare flexible and translucent devices have become the research hotspots in the field of new energy research in recent years. Among them, p-OS donor photovoltaic materials include conjugated polymers and organic small molecules. Compared with polymers, small molecular materials have certain molecular structures, no synthetic batch differences, and easy purification. Therefore, organic small molecule donor photovoltaic materials have also attracted widespread attention. All small molecules non-fullerene organic solar energy The use of p-OS small molecule donors and n-OS small molecule receptors, as well as the advantages of small molecule donor materials and non-fullerene small molecule receptor materials, has recently become an important research direction in the field of organic solar cells.
With the support of the pilot project of the Chinese Academy of Sciences, the research team of the Institute of Organic Solids of the Institute of Chemistry of the Chinese Academy of Sciences, Li Yongzhen, recently conducted a series of studies on the research of p-OS small molecule donor materials and all-molecular non-fullerene organic solar cells. Progress, making the energy conversion efficiency of all small molecule organic solar cells exceed 10%.
The p-OS small molecule donor material mostly adopts A-π-D-π-A type (where D represents the donor structural unit and A represents the acceptor structural unit) linear molecular structure. They are first developed in their use for non-rich Based on the J-series high-efficiency polymer donor photovoltaic material of the olefin polymer solar cell, the J-series polymer is small moleculed, and the benzodithiophene (BDT)-based donor unit is synthesized, and the fluorine-substituted trinitrogen is synthesized. The azole (FBTA) is the acceptor unit, and the acetonitrile ester group is the terminal receptor unit of the p-OS small molecules H11 and H12 (see Figure 1 for molecular structure). With H11 as the donor, n-OS small molecule IDIC is the receptor. The open circuit voltage (Voc) of the all-molecular organic solar cell reaches 0.977V, and the energy conversion efficiency (hereinafter referred to as efficiency) reaches 9.73% (J. Am. Chem. Soc. 2017, 139, 5085-5094.).
The n-OS small molecule acceptor material has the characteristics of an anisotropic conjugated backbone, thus optimizing the molecular structure of p-OS to regulate the morphology of the fully small active layer to form a good donor-receptor nanoscale phase separation. The interpenetrating network structure is an important means to improve the photovoltaic performance of all small-molecule organic solar cells. They use BDT as the central donor unit, and introduce the oligothiophene structure into the p-OS molecular structure to synthesize two p-OS molecules. SM1 and SM2 (see Figure 1 for molecular structure). The efficiency of SM1:IDIC-based small-molecule organic solar cells reaches 10.11% (Chem Mater. 2017,29,7543–7553.), which is a fully small molecule non-fullerene. Organic solar cell efficiency exceeded 10% for the first time.
In the two-dimensional conjugated polymer based on thieno-substituted BDT, the silane-based side chain can effectively reduce the HOMO level of the polymer, enhance the absorption and increase the hole mobility. To further improve the photovoltaic performance of the whole small-molecule organic solar cell. Recently, they introduced a two-dimensional BDT unit with a side chain of silylthiophene into the p-OS small molecule donor material, and synthesized two new p-OS small molecule donor photovoltaic materials H21 and H22. Figure 1), and the effects of different terminal acceptor units on the physical and chemical properties of materials and their photovoltaic properties were studied. The photoelectric conversion efficiency of H22: IDIC-based small-molecular organic solar cells was further improved to 10.29%. In Advanced Materials (Adv. Mater., 2018, 30, 1706361.).
Figure: Molecular structure of p-OS small molecule donor and n-OS small molecule receptor IDIC, device structure of all small molecule organic solar cells and energy conversion efficiency of all small molecule organic solar cells based on each donor material
