| Perovskite solar cells?PSCs?have developed rapidly in recent years Because of its unique photoelectric characteristics,simple preparation process,low cost and other characteristics,it has become the research focus of scientific researchers.Hole transport materials?HTMs?,as an important part of the structure of perovskite solar cells,restrict the performance of the device.The current optimization methods of hole transport materials still have limitations.In order to promote their further development,new design strategies based on planarity factors have been proposed.In this thesis,six kinds of D-?-D star-shaped hole transport materials were synthesized based on the planarity factor.Regulation of molecular planarity by changing the steric hindrance of the conjugated bridge chain,the central core and the planarity of the peripheral donor group.Then perform a performance study on it,mainly examining the planarity of the molecules to regulate the properties of hole transport materials.The first chapter summarizes the development and working principle of perovskite solar cells in recent years,the types and characteristics of hole-transporting materials,and reviews the star-shaped small-molecule hole-transporting materials.Finally,the design ideas of this article are presented:Properties of planarity to regulate material properties.Chapter 2 summarizes the previous work.We use carbazole as the nucleus,thiophene as the?bridge,and dimethoxytriphenylamine as the peripheral group.The hole transport material CS-42 and CS-43 is synthesized by changing the planarity between the carbazole and benzene ring.The molecular structure was also determined by nuclear magnetic resonance hydrogen spectrum and carbon spectrum.Performance analysis of the two revealed that the aromatic-immobilized material CS-43 had an HOMO energy level from-5.21 with an increase in planarity.The improvement is to-5.32 eV,the energy level gap with the perovskite valence band is reduced,the thermal stability is increased from 427°C to 440?,and the mobility is increased to 4.93×10-44 cm2V-1S-11 obtained a photoelectric conversion efficiency of12.12%(Voc=1.01 V,Jsc=19.87 mAcm-2,FF=58.75%),which is equivalent to the efficiency measured with the spiro-OMeTAD as a reference(Voc=1.07V,Jsc=19.79mAcm-2,FF=65.15%,PCE=13.72%).In chapter 3,a benzene ring is used as the nucleus,thiophene or benzene ring is used as the conjugated bridge chain,and indolin with different planarity is used as the peripheral donor group,a hole transport material with different planarity CS-44-CS-47 are synthesised,the structure of the compound was determined by nuclear magnetic resonance hydrogen spectrum and carbon spectrum.The planarity regulation of the entire molecule is achieved by changing the planarity of the conjugated bridge chain and the indoleline.In CS-44 and CS-45,CS-45 achieved better planarity by improving the planarity of the peripheral donor group.The HOMO energy level was shifted up by 1.2 eV,but the film-forming properties of CS-45 were still relatively low.Poor,so the perovskite solar cell device based on CS-45 has a short circuit and only obtains a PCE value of 2.01%.Although the final photovoltaic performance of the hole-transporting material CS-45 is not ideal,its performance is still greatly improved compared to CS-44,indicating that the research idea of the application performance of the regulating material through planarity is effective.Based on CS-45,CS-47 with better planarity was obtained by introducing thiophene.After testing,the HOMO energy level of CS-47 is further shifted by 0.04 eV compared to CS-45,and the thermal decomposition temperature is increased by 6°C.In addition,with the enhancement of planarity,the hole mobility of the material increased from 1.11×10-44 to 2.3×10-44 cm2 V-1S-1,and the root mean square after film formation decreased from 6.24 to 2.04.Therefore,CS-47-based PSC shows better performance,with a PCE of 8.67%.Chapter 4 Conclusion:Six hole-transporting materials were synthesized based on the method of planarization control.Through testing their properties,it was found that molecules with better planarity have better performance in all aspects.Compared with CS-42,the HOMO energy level of CS-43 is improved by 0.11 eV,the thermal decomposition temperature is increased by13°C,the hole mobility is increased to 4.93×10-44 cm2V-1S-1,and the photoelectric conversion efficiency of 12.12 is finally obtained;the HOMO energy level of CS-47 is compared with CS-44 moves up 0.16 eV,and the hole mobility is increased by2.3×10-4cm2 V-1s-1.Controlling the planarity will help improve the charge transfer efficiency and photovoltaic performance between interfaces,and provide new ideas for the development of new and efficient small molecule hole transport materials in the future. |
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