Growth Of Perovskite Single Crystal And Their Application For Photodetector

Organic-inorganic hybrid halide perovskite has triggered significant attention due to its suitable band gap,large optical absorption coefficient,long electron-hole diffusion length,benign defect physics,and low-cost solution processing.However,most of these optoelectronic applications focus on polycrystalline perovskite thin film or nanowires,which has amount of grain boundaries.The grain boundaries might be the dominating path for ion migration under the applied field in the polycrystalline thin films,because the lower energy barrier for ion migration within the grain boundaries.In addition,grain boundaries are the source of defects.However,perovskite single crystal(PSC)has potential advantages in stability and photoelectric property because of the absence of grain boundaries in it.The photodetectors based on singlecrystalline perovskite have demonstrated a certain degree of improvement in performance than that based on perovskite thin film.So PSC has been a new hot topic recently.The first main content of this thesis included growing PSC cube on a TiO2/FTO substrate by using anti-solvent method and fabricating narrowband photodetectors based on PSC cube.Before fabricated the PSC cube photodetectors,it need to remove the solvent.However,it was inevitable that there were vestigial solvent in the interface of TiO2/FTO,which could introduce interfacial defects and further lead to inconspicuous rectifying junction.Due to the interfacial defects close to the crystal surface,the excess carriers generated by short-wavelength light was strongly recombined.Hence,there was no photoelectric response in the short wavelength.Therefore,we performed a new design paradigm for a narrowband photodetector by utilizing this interfacial defects character.In order to further improve the performance of the devices,we performed a novel liquidlevel controlled heating method to grow thickness-controlled single-crystalline perovskite plate.Through strictly controlling the height of perovskite precursor solution,the flat space between the TiO2/FTO substrate and liquid level,the PSC was successfully grown along the direction of two-dimensional.This method consumed less time and economizes raw materials,which could reduce cost.In addition,it was a one-step method to grow PSC with less defects,and it was convenient to fabricated photodetectors without dry the solvent.Three single-crystalline perovskite(MAPbI3,MAPbBr3 and MAPbCl3)plates had been prepared,and the thickness of the single-crystalline perovskite plates could be controlled as thin as about 200 ?m.The plane size was about 2 mm × 2 mm.These single-crystalline perovskite plates were exploited to build high-performance photodiodes.The photodetector was high thermal stability,the ON-OFF ratio was 933 and the detectivity could be as high as 4.0×1011 Jones.Furthermore,we were committed to extend the detection into infrared or near-infrared range.The bandgap of PbS colloidal quantum dots could be adjusted from 0.4 eV to 2.0 eV,and the corresponding absorption was at 600-3000 nm.Hence,by introducing PbS into PSC and realizing effective separation of electric charge,it was expected to achieve infrared detection of PSC photodetector.By blending PbS colloidal quantum dots with absorption at 890 nm to PSC MAPbBr3,we successfully obtained high-quality PbS blended MAPbBr3 PSC.Compared with the photodetectors based on MAPbBr3 PSC,which could only response at 500-600 nm,the photodetectors response of PbS-MAPbBr3 PSC could be extended to 970 nm.