Fabrication And Optoelectronic Properties Based On Organic-inorganic Hybrid Perovskites

In recent years,solar cells based on organic-inorganic hybrid CH3NH3PbX3(X= Cl,Br and I)perovskites have attracted worldwide attentions.In just a few years,the energy conversion efficiency of perovskite solar cells has stridden from 4%to 22.7%.It was found that such organic-inorganic hybrid perovskite materials not only possess strong light absorption,high carrier mobility,long carrier lifetime,ease of band gap control,and solution-processable preparation,but also have extremely high photoluminescence(PL)quantum efficiency.Features such as high gain factor and lower defect state density make it attractive for development in light emitting diodes(LEDs),laser diodes(LDs),thin film transistors,and photodetectors.In this dissertation,structures,crystallization and PL of the bromine-based perovskite material(CH3NH3PbBr3)were systematically studied by means of scanning electron microscope(SEM),X-ray diffractometer(XRD),and spectral analyzer.The morphology of the perovskite film can be controlled by optimizing the film formation conditions.The bandgap of CH3NH3PbBr3 was tuned by the introduction of halogen elements Cl and I.On these bases,efficient and stable multi-color perovskite LEDs(PeLEDs)was designed and prepared.Details can be found in the following contents:1.Under the environment atmosphere,high-quality CH3NH3PbBr3 film was obtained via a two-step solution method by optimizing the speed of the spin-casted procedure,the annealing temperature,the annealing time and the molar ratio of precursors.The produced film has a low defect density and excellent light emitting properties,which makes it very suitable for use as a light emitting layer in PeLEDs.2.Under the environment atmosphere,hybrid perovskites(CH3NH3PbBr3-xClx and CH3NH3PbBr3-xIx)were also obtained via two-step solution method,through the introduction of halogen elements Cl and I.Unfortunately,we failed to obtain perovskite films with excellent optical and topographical properties by optimizing their growth conditions.Fnally,we used the one-step solution method and optimized its growth conditions.By adjusting the molar ratio,concentration,and annealing temperature of the precursors,we prepared CH3NH3PbBr3-xClx and CH3NH3PbBr3-xIx film with good film coverage and luminescence properties.3.Based on the above work,PeLEDs with the structure of ITO/PEDOT:PSS/CH3NH3PbBr3/PMMA/AZO/Ag were designed and prepared.The CH3NH3PbBr3 thin film was prepared by a one-step method or a two-step method under ambient atmosphere conditions.We found that the two-step solution impregnation deposition method is easier to obtain highly efficient and stable PeLEDs.At the same time,it is found that there is a large number of voids on the surface of the CH3NH3PbBr3 film deposited by a one-step solution method,resulting in leakage of the device and eventually leading to a rapid attenuation of light emission.To solve this problem we introduced an insulating polymethyl methacrylate(PMMA)polymer to form CH3NH3PbBr3/PMMA composite as the emitter,which ultimately boosted the light attenuation and instability caused by the leakage,and greatly improved performance of the PeLEDs without changing the film quality.Finally,cyan PeLEDs based on CH3NH3PbBr3-XClX were successfully fabricated and analyzed by introducing Cl into the CH3NH3PbBr3 lattice.