Study Of The Optoelectronic Performance Of Organic/Inorganic Nanocomposites And Organo-metal Halide Perovskites

This work is focused on novel optoelectronic devices based on organic/inorganic composite materials, including organic/inorganic nanoparticles composite materials based electrical bistable devices and organo-metal pervoskite based solar cells. The work can be divided into three parts:1. The Ag2S nanoparticles were synthesized by on pot-approach method. The morphology of Ag2S nanoparticles was studied by Scanning Electron Microscope method. The elemental composition of the Ag2S nanoparticles was characterized by X-ray diffraction. Then we fabricated electrical bistable devices based on Ag2S: PVK nanoparticles by spin coating method. The characteristics of the devices were studied by different methods.(?) The Ⅳ characteristics of the bistable devices with different PVK:Ag2S mass ratio was studied by electrical method and the On/Off ratio of the device was calculated. The optimal mass ratio of PVK:Ag2S composite was found. The hysteresis of the Ⅳ characteristics of the device was studied under different sweeping voltages.(?)The reproducibility and single state retention ability were studied by a programed test script. We found that the device’s charge carrier capacity can be remained after performing 102 times write-read-erase processes. The single state retention ability can be kept for 104s or longer time, which is good for the potential application of the device.(?) The performance of the device was studied after inserting a PMMA insulating layer between the function layer and the electrode of the device. By analyzing the results, we eliminate the possibility of the filament model.(?) We performed linear fitting of the IV characteristics of the devices at different voltage region by using different conducting models. The mechanism of the bistable device was further studied based on the fitting result.2. The sensitive response of the ITO/PEODT:PSS/Ag2S:PVK/Al bistable device was discovered by changing the oxygen concentration around the device. The temperature dependence of the device was studied by altering the device’s temperature and the conduction mechanism of the bistable device was further discussed.(?) We found that the device’s IV characteristics can be largely influenced by the surrounding oxygen concentration of the device. Under low oxygen concentration, the on state current of the device will decrease largely, while the off state current will rise up to a certain level. The On/Off ratio will drop greatly when th oxygen concentration is low.(?) Nitrogen flow was applied to the device and the write-read-erase measurement was carried out at the same time. The result showed that the On state and Off state current have instant responses to the nitrogen flow and the changing trend is consistent with IV characteristic measurement under different oxygen concentration.(?) The data fitting of the I-V characteristics for the devices was performed by using the different theoretical models of organic electronics. The result showed that the conducting model of the device varied under both different oxygen concentration and sweeping voltage region.(?) The temperature and testing parameters dependence of the device was studied by altering the device’s temperature and testing parameters. The working mechanism of the bistable device was further discussed.3. In this part, we select non-polarized and linearly polarized photoexcitations with the same intensity to elucidate how domain polarizations influence the charge dissociation, transport, and collection during the development of photovoltaic actions.(?) The perovskite solar cells were fabricated with the architecture of ITO/TiO2/ CH3NH3PbI3/PTB7/Au with the power efficiency of 13% under one-sun condition, after optimizing the thickness of the pervoskite layer.(?) The photo-polarizing effect in pervoskite solar cell device was studied by using non-polarized light and linearly polarized light. The result showed that the pervoskite solar cell device can generate larger photovoltaic parameters under the excitation of non-polarized light rather than linearly polarized light do.(?) The capacitance-frequency (C-f) and the ferroelectric measurement were carried out to study the photo-polarizing effect in pervoskite solar cell. The results indicate that linearly polarized light reduces the ferroelectricity of perovskite solar cell device.(?) The mechanism of the photo-polarizing effect was discussed base on the experimental results. We think that the ferroelectric domains inside the perovskite layer can be polarized by the linearly polarized light. The polarized domains can induce a negative effect on the photovoltaic process, namely reducing the Jsc, Voc, and FF.