The Study Of WOLED Devices Based On Complementary Color

White organic light-emitting diodes(WOLEDs),having advantages in high luminous efficiency,ultra-lightness,fast response speed,low power consumption,light emission,flexibility,as well as advantages in healthy eye protection,demonstrate their potential in the field of flat panel display devices and solid-state lighting technologies.It receives substantial attention from scholars and the industry.No matter fluorescent or phosphorescent,full-width at half maxima from organic light emission spectra covers a range up to 150 nm.In order to obtain a white light,it normally requires mixing three primary colors(red,green,and blue)or selecting two complementary colors(orange and blue)to cover the entire visible spectrum(380-780 nm).It is therefore at least two materials of different emission colors are needed in fabrication of WOLEDs,which is problematic in structure design and device instability.In this work,a simple WOLED structure was fabricated using two materials having complementary colors.Device performance were improved after optimisations.In this work,incomplete and complete energy transfer between blue fluorescent Bepp2(host)and orange-yellow fluorescent DCM(guest)against doping concentration were explored first.If the doping concentration was above 0.2 wt%,a complete energy transfer between the host and the guest will occur.WOLEDs were prepared based on Bepp2/DCM combination.Effects of doping concentrations,electron transport layer,and structure of the emitting layer on electroluminescence were investigated.The optimised device has a structure of Bepp2:DCM(0.1 wt%)in emitting layer and TPBi in electron transport layer,which demonstrated the highest current efficiency and mimimum color coordinates changes when operating current density was increased.When the current density changes from 20 mA/cm2 to 150 mA/cm2,or to 200 mA/cm2,the color coordinate change(?x and ?y)are(0.0037,0.0053),(0.0002,0.0031),respectively.If double light-emitting structure was used,a whiter color was achieved while the color stability was maintained.Finally,WOLED based on yellow phosphorescent material was used to replaced the DCM to produce a hybrid WOLED.Due to the triplet energy level of the host material is higher than that of the yellow phosphorescent material,it is not necessary to add a spacer layer and simplified device structure.The highest efficiency obtained is 45.6 cd/A.