Preparation Of Compact Layers In Perovskite Solar Cells And Study Of Their Photovoltaic Performance

Compact layer is one of the most important constitutes of the planar perovskite solar cell, its chemical composition and thickness have important influence on the photovoltaic performance of the planar perovskite solar cell, the study about the compact layer is meaningful to optimize the efficiency of the planar perovskite solar cell. In this thesis, WO₃ thin films with various thickness were firstly prepared by spin-coating-pyrolysis method using the ammonium metatungstate DMF/water solution, and applied as compact layers in planar perovskite solar cells, the photovoltaic performance of the fabricated planar perovskite solar cells with the structure of FTO/WO₃/CH₃NH₃PbI3/spiro-OMeTAD/Au was estimated and compared, and the influence of the rinsing treatment of CH₃NH₃PbI3 thin film with isopropanol on the photovoltaic performance of the corresponding perovskite solar cells was investigated. And the crystal phase, morphology and absorption spectra of WO₃ thin films were investigated by x-ray diffraction, scanning electron microscope and ultraviolet-visible spectroscopy, respectively. The ultra-thin and high-quality WO₃ compact layers were prepared by spin-coating-pyrolysis method using the tungsten isopropoxide solution in isopropanol, the crystal phase, morphology and absorption spectra of WO₃ compact layers were analysed, and the influence of WO₃ compact layer thickness on the photovoltaic performance of planar perovskite solar cells was investigated. Various thickness of TiO₂ compact layers were prepared by using a mildly acidic solution of titanium isopropoxide in isopropanol, the influence of TiO₂ compact layer thickness on the photovoltaic performance of planar perovskite solar cells was systematically investigated, and the interface charge transfer and recombination in planar perovskite solar cells with TiO₂ compact layers was analyzed by electrochemical impedance spectroscopy.The results revealed that The WO₃ thin films prepared by spin-coating-pyrolysis method appeared a preferred orientation along （110） plane with a high crystallinity, and the WO₃ thin films were compact and uniform. The planar perovskite solar cell based on the 62-nm-thick WO₃ thin film achieved the highest photoelectric conversion efficiency （PCE） of 7.18%, with open circuit voltage (V_oc) of 0.67 V, short circuit photocurrent density （Jsc） of 18.46 mA·cm^-2 and fill factor （FF） of 0.62, and the rinsing treatment of CH₃NH₃PbI3 thin film with isopropanol efficiently improved the photovoltaic performance of the corresponding perovskite solar cells. WO₃ compact layers prepared by this method were amorphous, ultra-thin and high-quality, and they could cover the underlying FTO uniformly and tightly. The planar perovskite solar cell based on the 15-nm-thick WO₃ compact layer obtained the highest PCE of 10.14%, with V_oc of 0.77 V, Jsc of 18.12 mA·cm^-2 and FF of 0.73. With the increase of WO₃ compact layer thickness, PCE and V_oc decreased with Jsc increased. TiO₂ compact layers prepared by spin-coating-pyrolysis method were amorphous or had low crystallinity, and they had a smooth surface with uniform, compact and pinhole-free. The planar perovskite solar cell with the 62-nm-thick TiO₂ compact layer gained the highest PCE of 12.64%, with V_oc of 0.92 V, Jsc of 19.16 mA·cm^-2, and FF of 0.71. With the increase of TiO₂ compact layer thickness, V_oc and Jsc decreased and FF increased, moreover, the recombination resistance decreased, that is, the possibility of the recombination between electrons and holes in perovskite solar cell.