Preparation Of Organic-Inorganic Hybrid Perovskite Materials And Application In Optoelectronic Devices

Organic-inorganic hybrid perovskite MAPbX3(MA:methylammonium;X:halide)materials are potential candidates for use in optoelectronic devices,including lasers,solar cells,photodetectors,photosensitive transistors,and light-emitting devices(LEDs),due to their unique features,such as broad and strong light absorption,longer carrier lifetime,long charge-carrier diffusion length,high carrier mobility and small exciton binding energy.At the same time,one attractive feature of hybrid perovskites as photovoltaic absorbers is that their bandgap(Eg)can be tuned continuously in several ways,such as alloying different halides into the structure.Forthermore,the most common method employed to fabricate perovskite materials is to spin-coat solutions on a suitable substrate,followed by annealing.However,this method requires controlled many kinds of the reaction conditions.To date,a facile and rapid method is still needed to synthesize perovskite materials.Facile solvothermal methods have been considered as most promising routes.In this disseration,we have synthesized the perovskite crystals by solvothermal method to apply in perovskite solar cells and photodetectors.The main results and innovations of the dissertations are as following aspects:1.CH3NH3PbX3(X=Cl,Br,I)crystals have been systematically synthesized using solvothermal process.The reaction conditions such as concentration of the precursor,temperature,time,lead source and halide source have been comprehensively investigated to obtain shape-controlled CH3NH3PbI3 crystals.The results showed that the CH3NH3PbI3 crystals exhibit tetragonal phase,CH3NH3PbBr3 and CH3NH3PbCl3 exhibit cubic phase,the CH3NH3PbI3 crystals change from nanoparticles to hopper-faced cuboids.Photoluminescence spectra of the crystals obtained with different lead sources show a blue shift due to the presence of defects in the crystals,and the peak intensity is very sensitive to the lead sources.Moreover,impurities(undesirable byproducts and excess components like HI or CH3NH2)presented during crystal growth can result in hopper growth.2.Mixed-halide hybrid perovskite CH3NH3Pb(BrxI1-x)3(0?x?1)crystals have been systematically synthesized in the full composition range by a solvothermal method.The as-synthesized crystals retained cuboid shapes,and the crystalline structure transitioned from the tetragonal phase to the cubic phase with an increasing Br-ion content.The photoluminescence(PL)of CH3NH3Pb(BrxI1-x)3 crystals exhibited a continuous variation from red(768 nm)to green(549 nm)with increasing the volume ratio of HBr(VHBr%),corresponding to a variation in the bandgap from 1.61 eV to 2.26 eV.Notably,the CH3NH3Pb(BrxI1-x)3(0.4?x?0.6)crystals exhibited obvious phase separation by prolonged illumination.The cause for the phase separation was attributed to the formation of small clusters enriched in lower-band-gap,iodide-rich and higher-band-gap,bromide-rich domains,which induced localized strain to promote halide phase separation.3.Based ong the CH3NH3PbI3 crystals synthesized by solvothermal,we dissolved the perovskite crystal in DMF to formate the precursor solution,which spin-coated on electron transfer layer and annealed to fabricate the Glass/Compact TiO2/Mesporous TiO2/MAPbI3/Spiro-OMeTAD/Au perovskite solar cells.We discussed the quality of perovskite films at different concentration of precursor solution.The morphology of films and performance of devices were tested using SEM and the Keithley 4200 source meter,the results shows that the dense and continuseof films have been parpared at 60 wt%,the PEC of perovskite solar cells is 8.49%,Jscis 20.36 mA/cm2,Voc is 0.79 V,FF is 0.524.4.Durable and stable UV-Vis perovskite photodetectors have been prepared on the interdigitated(IDT)patterned Au electrodes by spin-coating process to accomplish MSM perovskite photodetectors,the precursor solution is based on dissolving the pure CH3NH3PbI3 crystals synthesized via the facile solvothermal in DMF.The performance of device was tested using the Keithley 4200 source meter.The result shows that the photocurrent of device gradually increases upon increasing the power intensity,the on/off photocurrent ratio of the photodetector is about 3.77×102,the responsivity value of device reaches 6.66 mA/W.And photodetectors work best under red illumination and rise,decay times are estimated to shorter than 0.04 s and 0.05 s,moreover,exposing photodetectors to the red light illumination over 1000 s or stored 90 days,there are stable photocurrent signal,the results indicated that the perovskirte photodetector possess longer durability and using life exceeding 90 days.