Interface Engineering Of New Generation Solar Cells Based On Polymer And Organometal Halide Perovskite

Harvesting solar energy from photovoltaic cells is a promising approach to meet growing energy demand. Conjugated polymer exhibits excellent chemical adjustability by molecular design to tuning the properties of absorption and electricity. Qualified with excellent extinction coefficient, charge carrier diffusion length and ambipolar behavior, organometal halide perovskite is an ideal absorber in photovoltaic device. New generation solar cells based on polymer and organometal halide perovskite hold the promise for a cost-effective, lightweight solar energy conversion platform, which could benefit from simple solution processing of the active layer. Interface engineering has attracted much attention due to its outstanding function in improving the performance of polymer and perovskite solar cells. Focused on polymer solar cell and emerged perovskite solar cell, I develop and optimize kinds of electron and hole transport layers, and achieved improved efficiency based on these interlayers. My research mainly includes the following four parts:1. An in-situ cross-linked three-dimensional p ZA network has been used into ZnO nanoparticle film to passivate the defect. In passivated ZnO film, trap emissions is efficiently restrained and the corresponding device achieved improved performance. The results of transient photovoltage and transient photocurrent measurements indicate the cross-linked pZA network indeed passivates the ZnO NPs, leading to reduced defects in the ZnO film. Therefore, the trap-assisted recombination in the passivated device decreases. Compared to control device, the charge carrier lifetime in passivated device is 8.29 μs, exhibiting 27% enhancement. In addition, The ZnO film with cross-linked p ZA network is more dense and homogeneous, which enhanced the stability of device.2. Vanadium oxide with two-dimensional（2D） structure is employed as hole transport layer（HTL） in inverted polymer solar cell based on poly（3-hexylthiophene）（P3HT）: [6,6]-phenyl-C61-butyric acid methyl ester（PCBM） as active layer. The P3HT:PCBM device based on 2D vanadium oxide achieve power conversion efficiency of 4.19%. The value is 33% higher than one in device employing regular vanadium oxide as HTL. Owing to better conductivity and less trap in 2D material, device with 2D interfacial interlayer has smaller series resistance and decreased trap-assisted recombination.3. The influences of precursor components and annealing styles on film morphology and crystallization are investigated. The ratio of CH3NH3I:PbCl₂=3:1 in precursor results in the balance of morphology and crystallization, where the perovskite film possesses relatively dense morphology as well as stable and complete crystal structure. In addition, the quenched annealing benefits for enhancing film crystallization. Regarding to PCBM/Al interface in planar perovskite solar cell, proper interfacial modification can improve the contact and enhance device performance. Compared with LiF and PbO fabricated by vacuum evaporated, low-temperature and solution-processable polyethylenimine（PEI） and ZnO are better for improving device performance and stability.4. Graphene oxide（GO） is used as hole transport layer by replacing widely used conducting polymer（PEDOT:PSS）. The peovskite film grown on GO shows dense morphology. The grazing incidence X-ray diffraction（GIXRD） measurements indicate the peovskite film grown on GO posses better crystallization and plane orientation. The GO-based champion device achieves PCE of 12.4%, which is the highest reported efficiency then.5. We deposit a methylammonium iodide（MAI） layer on as-prepared perovskite film by spin-coating and the stacked film is annealed. The MAI post-treatment passivate the halogen defect in perovskite crystal. The treatment results in fused crystal morphology and enhanced crystallinity in perovskite film. We also prove the perovskite film is highly sensitive to post-annealing and solvent（IPA）. Our post-treatment strategy protects the perovskite from decomposing in post-annealing and enhances the resistivity of perovskite upon IPA. Benefited from the defect passivation and improved crystal quality, the device based on MAI post-treatment achieves PCE of 15.93%.