Photon-generated Electrons Transport And Yield In Organic Solar Cells

In1986, the bilayer heterojunction structure proposed by C. W. Tang made alandmark breakthrough for the organic solar cell. Nowadays, the power conversionefficiency of organic solar cell has exceeded for10%. The photocurrent is one of themost important parameters in the cell, so we focus our experiments on it based on thefollowing three aspects,Firstly, we introduced the n-type material,1,3,5-tri(phenyl-2-benzimi-dazolyl)-benzene (TPBi), as an electron extraction layer in the inverted polymer solar cell basedon poly(3-hexylthiophene):(6,6)-phenyl-C60-butyric acid methyl ester (P3HT:PCBM).In our experiment, the TPBi film was grown by vacuum deposition or solutionprocessing, and the photo-generated electron transporting characteristics wereinvestigated by the optical, electrical, energy level and morphology measurements. Thedata demonstrated that the TPBi film can perform good effect on reducing the workfunction of ITO substrate, decreasing the energy barrier for electrons transporting,modifying the substrate morphology. Therefore, TPBi interlayer in organic solar cell canimprove the photo-generated electrons transporting efficiency.Secondly， we explored the photon-generated electron property based onsmall-molecule organic solar cell, which copper phthalocyanine (CuPc) andmanganese phthalocyanine (MnPc) were chose as the electron donor material. In theCuPc base solar cell, the device photon-generated electron properties mainly depend onthe CuPc thickness and the ratio of CuPc:C60，and the results showed that the optimizedthickness was30nm and the best ratio was1:2. Meanwhile, MnPc was tried to replacethe CuPc in the devices, becauseβ-crystal MnPc has good ferromagnetism. Here, we were trying to utilize the photocurrent Hall effect caused by MnPc to improve thedevice photon-generated electrons transporting property.Thirdly, the pentacene was used to investigate the singlet fission effect on thephoton-generated electron property and the effect of magnetic field on the singlet fissionprocess in organic solar cells. According to the results, it could be concluded that thesinglet fission effect can improve the device photon-generated electron yield, however,the universality of this increase property caused by singlet fission need furtherinvestigation because of the singlet fission material limitation.