Study On Perovskite Optoelectronic Devices Based On Multilayer Structure Transparent Electrodes

Perovskite materials have been used widely in the research of solar cells,detectors,lasers and light-emitting diodes,which is attributed to its outstanding optoelectronic properties,such as high absorption coefficient,high carrier mobility,long carrier diffusion length,tunable bandgap,high photoluminescence quantum efficiency?PLQY?and high color purity.And now some progresses have been obtained.The highest power conversion efficiency?PCE?of perovskite solar cells?PSCs?has achieved 24.2%,showing super photovoltaic performance.Meanwhile,the external quantum efficiency?EQE?of the near-infrared and green perovskite light-emitting diodes?PeLEDs?has exceeded 20%,showing excellent electroluminescent?EL?properties.Both PSCs and PeLEDs show great commercial application prospects.According to recent products from global technology companies such as Samsung,Huawei,Apple and so on,the development of optoelectronic products is mainly oriented towards flexible smart-wearing and transparent integrated display.Therefore,it is very important to study and prepare highly efficient flexible PSCs and transparent PeLEDs to meet the development needs of the technological era.In this work,multilayer structure transparent electrodes have been introduced to fabricate perovskite optoelectronic devices,we hope to achieve highly efficient flexible PSCs and transparent PeLEDs by the design and optimization of electrode structure,the main contents and conclusions of this work are as follows:1.PSCs based on WO₃/Ag/WO₃?WAW?transparent electrodes.The multilayer structure transparent WAW electrodes have been prepared by electron beam thermal evaporation.And we introduce WAW electrodes into the fabrication of PSCs for the first time.Compared with ITO electrodes,it is found that the difference in surface roughness of different electrodes leads to different contact angles of the perovskite precursor solution on different substrates,which affects the heterogeneous nucleation rate of perovskite film and thus influences the growth of the perovskite crystal.A flat,dense,and uniform perovskite film has been obtained by optimizing the ratio of the composition in perovskite precursors.Finally,the maximum PCE of rigid and flexible PSCs based on WAW electrodes achieve 9.73%and 8.04%respectively,indicating WAW multilayer transparent electrodes have the potential application in PSCs.2.Flexible PSCs based on microstructured WAW transparent electrodes.A series of WAW multilayer transparent electrodes with different surface morphologies and structure have been fabricated by combining glancing angle deposition?GLAD?and electron beam thermal evaporation.A WAW electrode with tilted,ordered,scattered,porous WO₃ nanocolumns has been obtained when the deposition angle is 75°.The unique porous structure of WAW-75°electrode can effectively enhance the contact areabetweenholetransportingmaterials poly?3,4-ethylenedioxythiophene?-polystyrene sulfonate?PEDOT:PSS?and electrodes,improving the transportation and collection efficiency of hole,depressing charge recombination,and thus enhancing the PCE of PSCs.The rigid and flexible devices based on WAW-75°electrode show enhanced PCEs of 14.91 and 13.79%,which are increasing by 10.36 and 10.14%in comparison with the devices based on the WAW electrodes with planar structure,respectively.Meanwhile,the nanocolumns microstructure of WAW-75°electrode can release mechanical stresses under repeated bending,decreasing the damage on the perovskite layer,reducing the formation of grain boundaries,defect and pinhole,which enhance the bending durability of the flexible PSCs.The PCE of flexible devices based on microstructured WAW electrode can retain 90.97%of its initial PCE after 1000 times bending under the maximum strain of 1.3%,however the flexible PSCs based on the WAW electrodes with planar structure deteriorate seriously,the PCE has decreased to 78.39%of its original PCE,which confirms the application potential of microstructured WAW electrodes on fabricating flexible PSCs.3.Fabrication of highly efficient inorganic PeLEDs.The EL performance and stability of all-inorganic PeLEDs has been improved by morphology and interface engineering.A nonionic surfactant polyoxyethylene?20?sorbitan monolaurate?Tween20?is introduced into the CsPbBr₃,which improves the morphology of perovskite film,reduces the grain boundaries,passivates the defects at the crystal boundaries,decreases the defect density of perovskite layer and the nonradiative recombination rate,and improves photoluminescence?PL?intensity,PLQY and the uniformity of PL intensity distribution of perovskite film,resulting in a performance-enhanced PeLED with a highest brightness of 111000 cd m^-2,a peak current efficiency?CE?of 21.1 cd A^-1,a EQE of 5.55%,and an operational lifetime of 4.5 h.Meanwhile,the conductivity of PEDOT:PSS film has been improved by doping it with an anionic surfactant sodium dodecyl benzene sulfonate?SDBS?,which improves the transfer and injection of hole,and makes the injection of hole and electron more balanced,thus the EL performance and operational lifetime have been further increased.Finally,the optimal device displays an ultrahigh brightness of 179000 cd m^-2,a peak CE of28.0 cd A^-1,a maximum EQE of 7.39%,and a further prolonged operational lifetime of 6 h.Which provides a good foundation for further achieve efficient,transparent PeLEDs.