Investigation On Efficiency And Stability Of Perovskite Photoelectric Devices

In recent years,perovskite light-emitting diodes?PeLEDs?have attracted increasing attentions due to its advantages such as low cost,solution preparation,high color purity,and tunable band gap.At present,the external quantum efficiency of PeLED has been equivalent to that of traditional organic light-emitting diode?OLED?,indicating its great potential in flat panel display and solid-state lightening.However,there are still unresolved problems,such as the sensitivity of organic-inorganic hybrid perovskites to water and oxygen molecules,easy decomposition,and poor thermal stability.In contrast,the all-inorganic perovskite material CsPbBr₃ has better stability.Therefore,further improving the efficiency of CsPbBr₃ and optimizing the preparation process are expected to prepare PeLEDs with higher efficiency and batter stability,helping the industrialization of PeLEDs in the field of flat panel illumination and display.Metal halide perovskites not only achieve amazing results in the field of illumination,but also become a star in the field of photovoltaics.In recent years,the power conversion efficiency?PCE?of metal halide perovskite solar cells?PSCs?has rapidly increased from 3.8%in 2009 to the current 23.7%,approaching the PCE of silicon solar cells?26%?.Thus,PSCs have been hailed as one of the most promising scientific research projects by Nature.After years of research,perovskite solar cells have made continuous breakthroughs,but the issue of high cost,lower stability of PSCs,toxic lead?Pb?contaminant have limited the development of commercialization.In this thesis,our goal has focused on improving the efficiency and stability of perovskite light-emitting diodes and solar cells,researching and developing environmentally friendly materials and technology from the perspective of environmental protection,and study the internal mechanism of device.The paper mainly includes the following aspects:In chapter 1.Firstly,we have introduced the development status and basic concepts of PeLEDs,such as device structure,working mechanism,important parameters.Secondly,the basic situation of PSCs is introduced,including the development tendency,process technology of devices,important parameters and the problems needing to be solved.Finally,there is a brief introduction on the main research contents of this paper.In chapter 2.PeLEDs based CsPbBr₃ system have fabricated by utilizing a simple,effective and low-temperature method that is only pumping away after one-step spin coating of the solution.This method avoids high temperature processing.And the coverage of modified film is improved by 19.4%to 91.1%compared to the reference film.Moreover,the perovskite grain size is reduced,which will reduce the internal defects,non-radiative transition,current leakage and improve electroluminescent performance.The maximum luminance of champion device is improved 30 times compared with reference device.In chapter 3.Based on the previous research,we have continued to optimize and adopted a novel precursor solution processed method by combining CsPbBr₃ with phosphorescent material FIrpic to produce high-performance LEDs.By adjusting the doping concentration to study the role of FIrpic in the luminescent layer,the singlet excitons in FIrpic can be transfer to the triplet state through the inter-system transition achieving efficient energy transfer between the energy levels and obtaining high quality perovskite film.As a result,the optimal device shows a maximum luminance of5486 cd m^-2,and an external quantum efficiency of 0.47%,which are 1.84 and 1.76times that of neat CsPbBr₃ PeLEDs,respectively.In chapter 4.Hole-transporting materials?HTMs?play an important role in hole transport and extraction for PSCs.As an important type of HTMs,the spiro-architecture-based material is widely used as small organic HTM in PSCs.Besides,carbazole,as an important electron-rich block,is once developed as star-shape HTMs.Therefore,we have incorporated the carbazole block into spiro-skeleton to form a novel carbazole-based single-spiro-HTM named SCZF-5.The SCZF-5 has relatively high hole mobility value of 4.69×10^-44 cm² V^-11 s^-1,excellent thermal stability Finally,20.10%PCE is achieved in the SCZF-5 based PSCs,which is superior to the one based on the commercial hole transport material Spiro-OMeTAD?19.11%?.In chapter 5.In order to further develop low-cost and high-performance HTMs,it is critical to explore new molecular skeleton in this field.we chose rigid molecular DCZ as the central building block and arylamine as the electron-rich branch to synthesize new HTMs.It is found the change from spirobifluorene to DCZ leads to the enhancement of hole-transporting ability and the increase of the highest occupied molecular orbital?HOMO?level.As a result,a relatively high PCE of 19.81%and21.66%was achieved by DCZ-OMeTAD,significantly higher than that of devices based on Spiro-OMeTAD?18.06%and 20.08%?and DCZ-OMeTPA?17.08%and19.02%?in an identical configuration.The results provide a significant method for the commercialized application of PSCs.In chapter 6.The above works are summarized.And then prospects for future academic research in PeLEDs and PSCs are presented.