Fabrication And Investigation Of White Polymer Light-emitting Devices Based On Star-shaped Polymers

White polymer light-emitting devices?WPLEDs?,which are well known as a new generation of display,have wide market prospect for their great advantages in full-color flat-panel displays and solid-state lighting sources.However,due to the low efficiency of energy transfer,the lifetime of devices becomes shorter,which is still a bottleneck problem to be solved urgently.At present,there are two main strategies to realize WPLEDs:the traditional one is polymer blend system;the second is single white polymer system.But the phase separation will lead to short lifetime of devices.For the single white polymer system,most of researchers focus on developing new polymers,and the research on the emitting mechanism are rarely found.In current work,two star-shaped polymers are used to fabricate WPLEDs,by comparison of the electrical properties and emitting properties,the energy transfer process are analyzed and the relationship between the structure of polymers and device performances are debated.The concrete research is below:?1?A series of white polymer light-emitting devices?WPLEDs?were fabricated by utilizing the star-shaped white-emission copolymers containing Ir?piq?₃,fluorenone?FO?and poly?9,9-dioctylfluorene??PFO?as red-,green-and blue-emitting?RGB?components,respectively.In these WPLEDs,a maximum current efficiency of 6.4 cd/A at 20 mA/cm and the current efficiency was still kept to 4.2 cd/A at the current density of 200 mA/cm.By comparing the fluorescent decay lifetimes of PFO chromophores in the four star-like white-emitting copolymers,the efficient energy transfer from PFO units to Ir?piq?₃ and FO chromophores was confirmed.The efficient energy transfer as well as reduced intermolecular interactions contributes to the enhanced device performances compared to the linear single-polymer white-light systems.And the saturated stable white emission result from the joint of energy transfer and trap-assisted recombination.?2?In order to reduce aggregation-caused quenching of single white polymers,three kinds of star-shaped polymers with aggregation-induced emission?AIE?are used to fabricate WPLEDs,and a Commission Internationale d^'Eclairage?CIE?coordinates of?0.33,0.32?were achieved.By comparison with photoluminescence of polymers at different conditions,the mechanism of AIE by reducing the energy of molecular rotation in these polymers is investigated,and the relationship between the AIE and energy transfers is analyzed to enhance the device performance by radiation process.In summary,this work has provided the foundation for fabrication of WPLED with high luminous efficiency and high color saturation by researching luminous mechanism of the two serials of star-shaped polymers.