Ultrahigh Energy Gap Hosts in Deep Blue Organic Electrophosphorescent Devices

Abstract

Four ultrahigh energy gap organosilicon compounds [diphenyldi(o-tolyl)silane (UGH1), p-bis(triphenylsilyl)benzene (UGH2), m-bis(triphenylsilyl)benzene (UGH3), and 9,9‘-spirobisilaanthracene (UGH4)] were employed as host materials in the emissive layer of electrophosphorescent organic light-emitting diodes (OLEDs). The high singlet (∼4.5 eV) and triplet (∼3.5 eV) energies associated with these materials effectively suppress both the electron and energy transfer quenching pathways between the emissive dopant and the host material, leading to deep blue phosphorescent devices with high (∼10%) external quantum efficiencies. Furthermore, by direct charge injection from the adjacent hole and electron transport layers onto the phosphor doped into the UGH matrix, exciton formation occurs directly on the dopant, thereby eliminating exchange energy losses characteristic of guest−host energy transfer. We discuss the material design, and present device data for OLEDs employing UGHs. Among the four host materials, UGH2 and UGH3 have higher quantum efficiencies than UGH1 when used in OLEDs. Rapid device degradation was observed for the UGH4-based device due to electro- and/or photooxidation of the diphenylmethane moiety in UGH4. In addition to showing that UGH materials can be used to fabricate efficient blue OLEDs, we demonstrate that very high device efficiencies can be achieved in structures where the dopant transports both charge and excitons.

Highly Efficient and Stable Narrow‐Band Phosphorescent Emitters for OLED Applications

“…Such advantages are essential for potentially achieving both high efficiencies and long operational lifetimes for blue phosphorescent OLEDs. [27] This result highlights the benefits and importance of narrow-band emitters to tune the emission to the precise colors desired in order to achieve the most efficient and high color purity devices possible.…”

Thermally Activated Delayed Fluorescence Emitters for Deep Blue Organic Light Emitting Diodes: A Review of Recent Advances

“…Recently, Hatakeyama et al reported a new strategy to design effective deep blue triarylboron based emitters [95]. The chemical structures of boron emitters (28)(29) are given in Figure 6, while their novel design strategy is displayed in Figure 7. It is well known that efficient TADF-based OLEDs need a fluorophore with a small ∆E ST .…”

Solution-Processed Blue/Deep Blue and White Phosphorescent Organic Light-Emitting Diodes (PhOLEDs) Hosted by a Polysiloxane Derivative with Pendant mCP (1,3-bis(9-carbazolyl)benzene)

“…29,30 Furthermore, a larger HOMO-LUMO energy gap (E g ) than the phosphorescent guest is required to ensure direct charge trapping on the emitter. 31 Carbazole derivatives are established as hosts for PhOLEDs due to carbazole's high triplet energy and favorable hole-transporting properties. [32][33][34][35] The small-molecule mCP [1,3-bis(9-carbazolyl)benzene] which has a triplet energy of 2.9 eV is widely used in this context.…”