| In recent years,organic-inorganic hybrid perovskite solar cells（PSCs）have attracted extensive research interest due to their efficient light-harvesting capability over a broad wavelength region,adjustable bandgap with high defect tolerance,and simple solution preparation process using low-cost materials.However,the high temperature preparation of the conventional TiO2 electron transport layer,the doping and oxidation treatment of the hole transport layer Spiro-OMeTAD,and large bulk and interfacial defects in the perovskite devices limits their future large-scale applications.This thesis mainly discusses the synthesis of metal oxide semiconductor materials by a low temperature preparation process,improving the device internal trap density through interfacial or bulk modification,thus increasing device photovoltaic performance.The research is divided into the following aspects:（1）Through the low-temperature sol-gel reaction,using titanium tetrachloride as the precursor,with ethanol and benzyl alcohol as mixed solvents,the preparation conditions can be optimized to obtain TiO2 nanoparticles with high crystallinity.Diacetylacetone diisopropyl titanate（TIPD）is used as an additive to disperse the nano-particles in the final dispersion.After the low-temperature thermal treatment,the film became compact enough and the fullerene derivatives were introduced at the interface between perovskite and TiO2 layer to reduce the trap density.Device performance was significantly improved to 20.3%with negligible hysteresis,while achieving stable power output.（2）Conjugated polymers based on carbazole and benzothiadiazole were used as the hole transport materials（HTMs）for device preparation.Through molecular structure design,they were rendered with excellent charge transport properties,a hydrophobic surface and defect passivation ability.Functional conjugated polymers act as dopant-free HTMs for perovskite devices.Studies have shown that the conjugated polymer PCDTBT1 grafted with a methoxy side chain can act as an effective HTM;the hole defect density of the device is effectively reduced through the cooperative passivation of thiophene and methoxy groups.Therefore the fabricated devices show highest performance as well as no obvious hysteresis,which is comparable to traditional Spiro-OMeTAD based device.Furthermore,PCDTBT1does not require doping and post-oxidation treatment to improve device performance,greatly simplifying the preparation process of perovskite devices.（3）Based on the optimization of the electron transport layer and the hole transport layer,a novel two-step fabrication process was designed through incorporating an ionic salt additive trimethylammonium chloride（TACl）into methyl iodide（MAI）isopropanol solution to manipulate the nucleation and crystallization process of perovskite crystals,resulting in larger grain size and fewer grain boundaries in the perovskite polycrystalline film.In addition,the dual defect passivation of trimethylammonium cations and chloride ions to the perovskite can effectively reduce the bulk defect density of perovskite,accelerate the charge transport and suppress charge carrier recombination,increase the charge diffusion length,and ultimately achieve a maximum PCE of 20.9%by a low-temperature process without dopant in the hole transport layer,using MAPbI3 as the photoactive layer. |
