Liang-Chen Chi

A new benzimidazole/carbazole hybrid bipolar material for highly efficient deep-blue electrofluorescence, yellow–green electrophosphorescence, and two-color-based white OLEDs

The bipolar molecule CPhBzIm exhibits an excellent solid state photoluminescence quantum yield (ΦPL = 69%), triplet energy (ET = 2.48 eV), and bipolar charge transport ability (μh ≈ μe ≈ 10−6–10−5 cm2 V−1 s−1). We have used it to fabricate a non-doped deep-blue organic light emitting diode (OLED) exhibiting promising performance [ηext = 3%; CIE = (0.16, 0.05)] and to serve as host material for a yellow–green phosphorescent OLED [ηext = 19.2%; CIE = (0.42, 0.56)]. Exploiting these dual roles, we used CPhBzIm in a simple singly doped, two-color-based white OLED (ηext = 7%; CIE = 0.31, 0.33).

A diarylborane-substituted carbazole as a universal bipolar host material for highly efficient electrophosphorescence devices

Recently bipolar phosphorescent host materials have attracted wide attention since they can achieve better charge balance and hence better device performance. In this work, we report the synthesis and physical properties of a novel bipolar host material containing the dimesityl borane/carbazole hybrid, CMesB. With a high triplet energy, CMesB is considered a promising universal host material and has been applied to phosphorescent OLEDs of various colors. Red/green/blue/white (RGBW) OLEDs based on CMesB all show high external quantum efficiencies (20.7% for red, 20.0% for green, 16.5% for blue, and 15.7% for white) at practical brightnesses. The results indicate that the bipolar host CMesB with high triplet energy has high potential in manufacturing RGBW OLEDs for display or lighting applications.

High-luminescence non-doped green OLEDs based on a 9,9-diarylfluorene-terminated 2,1,3-benzothiadiazole derivative

We have prepared a highly efficient non-doped green organic light-emitting diode (OLED) incorporating a novel 9,9-diarylfluorene-terminated 2,1,3-benzothiadiazole green emitter (DFBTA), which exhibits an excellent solid state photoluminescence quantum yield (81%), and new triaryldiamines (DPAInT2, DPAInF) with high hole mobility derived from rigid and coplanar cores. The optimal device: ITO/DPAInT2/DPAInF/TCTA/DFBTA/Alq3/LiF/Al displayed impressive device characteristics, including a maximum external quantum efficiency (ηext) of 3.7% (12.9 cd A−1) and a maximum brightness at 168 000 cd m−2.

An ambipolar host material provides highly efficient saturated red PhOLEDs possessing simple device structures

A highly efficient red electrophosphorescent device exhibited saturated red emission and an impressive external quantum efficiency [eta(ext) = 10.8% (ph/el)] with simple device configuration of doping an iridium complex (Mpq(2)Iracac) into a novel ambipolar spiro-configured donor-acceptor host material (D2ACN) has been developed.

Photoinduced charge separation in donor–acceptor spiro compounds at metal and metal oxide surfaces: application in dye-sensitized solar cell

Modulated charge separation has been investigated by surface photovoltage spectroscopy in the fixed capacitor arrangement for four different fluorene compounds adsorbed from highly diluted solutions at ultra-thin nanoporous TiO2 (np-TiO2), Au and ITO surfaces. Donor (–N(C6H5)2) and acceptor moieties (–CN, –COOH) were linked by fluorene or spirobisfluorene cores and the chain length has been changed by introducing thiophene. Modulated charge separation by electron injection and intramolecular transport has been separated and directed adsorption of spiro compounds at Au surfaces has been demonstrated. Striking differences between the interaction of linking –CN and –COOH groups and the different substrates were observed. The capability as TiO2 spectral sensitizer of spirobisfluorene donor–acceptor molecules with extended conjugation has been demonstrated. Solar cells exhibit 5.6% energy conversion efficiency, confirming that spiro-configured geometry is a promising route to the design of metal free dyes.