A novel intermediate connector with improved charge generation and separation for large-area tandem white organic lighting devices†
An intermediate connector (IC) consisting of lithium (Li) doped 4,7-diphenyl-1,10-phenanthroline (BPhen)/Al/tetrafluoro-tetracyanoquinodimethane (F4-TCNQ)/1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) is developed for fabricating tandem white organic light-emitting diodes (WOLEDs). An investigation of the charge generation and separation process in Bphen:Li/Al/F4-TCNQ/HAT-CN, which is carried out by analysis of the current–voltage and capacitance–voltage characteristics, shows that the proposed IC structure is suitable as a connecting unit in tandem OLEDs. The tandem WOLED based on a silicon compound host material of 10-phenyl-2′-(triphenylsilyl)-10H-spiro [acridine-9,9′-fluorene] (SSTF) with the proposed IC structure exhibits a maximum current efficiency of 159.2 cd A−1 and a maximum power efficiency of 69.4 lm W−1. For application in large-area OLEDs, a 150 × 150 mm2 tandem lighting panel with maximum efficiencies of 231.8 cd A−1 and 52.9 lm W−1, correlated color temperature of 3000 K and Commission International de I'Eclairage (CIE) coordinates of (0.34, 0.45) is also demonstrated.