The Characterization Of Modified Sequential Deposition Fabrication Of Perovskite Solar Cells Based On TiO₂

Nano-Ti O₂ is an important inorganic semiconductor material, and has good heat-resistant, resistance chemical corrosion, notoxicity, insolubility, high refraction coefficient and other characteristics. Ti O₂ nano-materials have the sensitive nature of the gas-sensitive, pressure-sensitive, light-sensitive and excellent optical properities. And its ability to absorb ultraviolet light is stranger. So Ti O₂ nanomaterials have broad application in sensitive element, photocatalyst, solar cell. The nano-Ti O₂ is as an electron-transporting material in the perovskite solar cells and plays an important role to improve the photoelectric conversion efficiency of solar cells. In this paper, we prepared electron-transporting layer of Ti O₂ with the different deposition methods and modified the sequential deposition method for fabrication of perovskite solar cells based on Ti O₂ for a higher efficiency. The main contents of this thesis as follows:（1） We prepared the Ti O₂ electronic-transporting layer（hole-blocking layer） by spin coating, spray pyrolysis and atomic deposition（ALD） methods to fabricate the perovskite solar cell devices. The devices performance was characterized by scanning electron microscopy（SEM）, X-ray diffraction（XRD） spectra and current-voltage（I-V） to compare the Ti O₂ compact layers prepared with three different depositions. ALD-Ti O₂-based device exhibited power conversion efficiency of 7.84%. The device obtained 6.06% by using spray pyrolysis and the efficiency of the spin coating-Ti O₂-based device was only 3.23%. As the images of SEM, the surface morphology of ALD-based compact Ti O₂ layer lacked visible pinholes and the spray pyrolysis-based compact layer had a few pinholes near the wrinkles caused by very small Ti O₂ particles. For spin coating-based compact Ti O₂ layer, the surface morphology existed a few nanometers in size that made the compact layer could not transport the electron and block the hole efficiently leading to higher series resistance, lower shunt resistance and lower efficiency.（2） We modified the traditional sequential deposition to improve the power conversion efficiency of the perovskite solar cell based on Ti O₂ electron-transporting layer. The coverage of large crystals in the perovskite capping layer was well increased and the no residual of Pb I2 by controlling the concentration of Pb I2 solution, the dipping time, the reaction temperature and the pre-coating in CH3NH3 I solution. In the SEM images, the large crystals in the capping layer decreased with the concentration of Pb I2 lower to 0.8M and increased with longer dipping time and higher reaction temperature. The optimum process parameters with pre-coating low concentration of CH3NH3 I solution, 1M Pb I2 solution and the dipping time of 10 min can produce PSC devices with photocurrent up to 19.4m A·cm-2and power conversion efficiency of 12.9%. And the thickness of perovskite was about 300 nm. The efficiency of the perovskite solar cells can be well improved with the compact and continuous capping layer.