Design,Synthesis And Optoelectronic Properties Of Novel Organic Small Molecule Photovoltaic Materials

Interfacial engineering and morphology engineering have been identified recently as essential approachs to form aximizing power conversion efficiency of polymer and hybrid perovskite solar cells.Interfacial materials are the materials to modify the interfaces between activelayers and electrodes, the nature of electrical contact of these organic/electrode interfaces will significantly affect the resulting photovoltaic performance including open-circuit voltage(Voc), short-circuit current(Jsc), and fill factor(FF). It is possible for Interfacial materials to provide orthogonal solvent processability relative to BHJ layers through proper molecular design to meet the requirement of high throughput manufacturing processes.With the improving of the PCE, morphology engineering has been identified recently as an essential approach form aximizing power conversion efficiency of BHJ organic solar cells. We tried to develop new molecular chemical structure of active layer materials, find the best ratio of donor and acceptor, use different manufacturing processes and so on, just to control the morphology of activelayers. Another important way is to add addtives into active layers.Organic-inorganic hybrid perovskites CH3NH3PbX3(X = Cl, Br, I) have emerged as a useful materials component in photovoltaic and optoelectronic applications. However, crystalline perovskites tend to contain a high density of defect states, and they exhibit a high degree of disorder. Trap states at the surfaces and grain boundaries of perovskite crystals suggest that these traps may act as non-radiative recombination centers, which lead to solar cell photocurrent hysteresis. In chapter two, taking all the issues discussed above into consideration, and electron-rich molecules can efficiently passivate the surface traps, we combined electron-rich functional groups with fullerenes to design a new series of hydrophilic fullerene derivatives. By adjusting the numbers of OE chains, relevant properties such as the energy levels, charge carrier mobilities, surface energy and dipole layer features could be tuned at the interfaces. We found that the passivation effect should be considered through a comprehensive analysis related to several parameters, including energy levels, carrier mobilities, surface energy and dipole intensity. Furthermore, analysis using controlled electron density in ETLs was carried out to examine the underlying mechanism of passivation. The results suggest a design strategy for the development of high-performance fullerene derivatives for use as ETLs in PVKSC applications.In chapter three, we designed and synthesized two D-A dyads fullerene derivatives as compatibilizers applied into active layers as addtives. Then we tested their optical and electrical properties, as well as the calculate through density functional theory. While after applying them into organic small molucule solar cells, organic polymer solar cells and organic tenary solar cells, we studied photovoltaic performances of the final devices. At the same time, we also studied the thermal stability and time stability of these devices. Although the final devices performances are not very satisfactory, we studied natural characters of these two dyads deeply and provide some refurential significance about how to control morphology of active layers in OPVs.In chapter four we designed and synthesized a new crosslinkable small molecule with terminal olefinic, then measured its basic properties as optical properties, thermal properties and electrical properties. We introduced it into hole transport layer of organic small molecule solar cells and tried to promote hole transporting, hole extracting and obstructing electron to improve the performances of devices. Through this work, the results suggest a design strategy for the development of crosslinkable molecule, we expect that further refinement should be possible with respect to this experience.In chapter five we further studied another two alcohol soluble fullerene derivatives as electron transport layers in organic polymer solar cells, then measured their basic properties as dissolution properties, optical properties, thermal properties and electrical properties. We firstly introduced it into electron transport layers of organic polymer solar cells to study the effects after applying them on performances of devices through orthogonal solvent manufacturing processes.