Effect Of In-Situ Heat Treatment On Efficiency Improvement Of OLED Devices And TADF Effect On Blue Light Devices

The study focused on two research fields.First,this paper improved the OLED light-emitting device performance by using the method of in-situ heat treatment.For the B-PHOLED,the in-situ heating increased the peak power efficiency(PE)by more than 30%with the increasing heating temperature from the room temperature to 100? accompanying with negligible effects on the blue light color stability.However,the optimal in-situ heating temperature of 100? for B-PHOLED was not beneficial to the PE of the W-PHOLED,but greatly facilitated the white light color stability.The GR-PHOLED revealed the similar PE dependence on the in-situ heating as those of the W-PHOLED as well as the deteriorated color stability upon in-situ heating.The mechanism responsible for those characteristic temperature dependence of the EL performance was investigated focusing on the surface morphology related carrier transportation and carriers mobility related excitons decaying.Second,The high efficient blue phosphorescent organic light emitting diodes(PHOLEDs)employing ultrathin Firpic layer sandwiched between electron donor mCP and electron acceptor TmPyPB layers were fabricated,and the dependence of the electroluminescence(EL)performance on the ultrathin Firpic layer thickness were investigated.It was found that the Firpic layer thickness imposed vital influence on the OLEDs EL efficiency and the one with the 0.3nm Firpic demonstrated the optimal power efficiency(PE)of 50 lm/w and the external quantum efficiency(EQE)close to 18%.The sandwiched ultrathin Firpic layer would not impede the formation of the exciplex between mCP and TmPyPB,and the balance between the exciplex formation and exciplex decaying showed strong dependence on Firpic layer thickness and imposed vital influence on the energy transfer,fluorescence and phosphorescence inside the emissive layer.There were three radiative decaying processes involved,i.e.the prompt and delayed fluorescence(PF and DF)of the exciplex as well as the phosphorescence(PH)of the Firpic,and the final EL relied on the competition of those processes.