Confined Crystallization Strategy For Controllable Growth Of Organic-inorganic Hybrid Perovskite Single Crystals And Their Application In Photodetectors

Organic-inorganic hybrid perovskite（OIHP）single crystals（SCs）show extraordinary potential in the field of photodetection due to their low trap density,excellent optoelectronic properties,and superior stability.However,these currently reported solution-processed methods are difficult to accomplish dual control of crystal size and thickness,which limits the application of perovskite single crystals（PSCs）in large-area,high-performance,and near-infrared photodetectors.Aiming at these critical issues,this thesis develops the confined crystallization strategy to realize the controllable growth of PSCs and their high-efficiency photodetection applications in the visible to near-infrared（NIR）region.the main research contents are as follows:1.A Three-dimensional confined crystallization strategy for controllable growth of large-area organic-inorganic hybrid perovskite single-crystal arrays toward high-performance photodetectorIn this work,we develop a three-dimensional confined crystallization（3DCC）strategy to realize the preparation of centimeter-scale and thickness-controllable CH₃NH₃Pb I₃（MAPb I₃）SC arrays,and construct the high-performance lateral-structured photodiodes based on MAPb I₃ SC arrays.In this strategy,the soft elastomer blade is tightly attached to the surface of the microchannels to create enclosed 3D microchannels,so that can offer 3D geometrical confinement for the perovskite crystal growth.Fluid dynamics simulation and experimental results indicate that the enclosed 3D microchannels can not only induce spontaneous capillary flow,so as to enhance the mass transport speed by more than 100 folds compared with the conventional method,but also can effectively confine both in-plane and out-of-plane crystallization of the crystals during blade coating process,thereby ensuring high crystallization quality over a large area and achieving precise control of crystal thickness.Through this method,we obtain centimeter-level（2×2 cm²）,highly oriented PSC arrays with precise thickness control ranging from 500 nm to 5μm.The prepared MAPb I₃ SC arrays exhibit good monocrystalline characteristics and excellent photoelectric properties,where the carrier lifetime is as long as 95.57 ns and the trap density is as low as 8.5×10¹⁰ cm^-3,which is comparable to the reported bulk SCs.Furthermore,the lateral-structured photodiodes based on MAPb I₃ SC arrays can serve as self-driven photodetectors,and the unpackaged devices exhibit high specific detectivity of 5.06×10¹⁰ Jones,wide linear dynamic range of 73 d B,and long-term stability over 36 days.Our 3DCC strategy provides new insights into the controllable preparation of large-area and high-quality PSCs,opening a pathway for the application of PSCs in large-scale optoelectronic integrated devices.2.Low-temperature spatially-confined crystallization strategy for preparation of low-bandgap Sn-Pb perovskite single crystals toward near-infrared photodetectorsIn this work,we have successfully prepared high crystalline quality MA_0.9FA_0.1Pb_0.9Sn_0.1I₃ SCs by doping tin into lead-based perovskite via a low-temperature spatially-confined crystallization strategy and demonstrated its applicability in near-infrared（NIR）detection.In this method,the perovskite precursor solution is confined at micro-sized gaps,which can effectively slow down the crystallization rate of Sn-Pb perovskite to avoid uncontrollable morphology,disordered grain orientation,and phase separation.Simultaneously,inverse temperature crystallization（ITC）is performed at a lower temperature（40°C～80°C）to avoid the loss of halide components and consequent degradation of perovskite crystal caused by thermal triggering in conventional ITC methods（≥100°C）,which can further improve the crystalline quality.Herein,as-grown MA_0.9FA_0.1Pb_0.9Sn_0.1I₃ SCs have a smooth surface,no grain boundaries,and phase separation,and simultaneously display a clear band edge cutoff at 920 nm.Furthermore,we demonstrate a photodiode based on the resultant MA_0.9FA_0.1Pb_0.9Sn_0.1I₃ SCs with excellent optoelectronic performance and operational stability,including fast response time of 20.35μs,wide linear dynamic range of 87.2 d B,and high specific detectivity of1.6×10¹⁰ Jones.Finally,we further investigated the application of MA_0.9FA_0.1Pb_0.9Sn_0.1I₃SCs photodiodes in photoplethysmography testing and image sensing.Among them,the fast-responding photodiode enables pulse detection with a good signal-to-noise ratio.The photodiode with good operational stability is prepared as a single pixel for imaging purposes,which perfectly presents the image of a 12×12 pixel array.This work provides an effective route for the development and practical application of Sn-Pb PSCs in the field of NIR detection.