455 477 (28) 0.43 0.9×10 The OLED device stack and the chemical structures of the organic layers are shown in Figure and 7b. The device data are summarized in Table . We first fabricated OLEDs with a higher concentration of 4 wt% emitters in SF3-TRZ as the EML as it was hypothesized that a higher concentration of emitter would contribute to improve the charge balance and enlarge the exciton recombination zone. .