Guojian Tian

A new D–A–π–A type organic sensitizer based on substituted dihydroindolo [2,3-b] carbazole and DPP unit with a bulky branched alkyl chain for highly efficient DSCs

Two new D–A–π–A configuration metal-free organic sensitizers (T1–T2) based on 5,7-dihexyl-6,12-diphenyl-5,7-dihydroindolo[2,3-b]carbazole and a DPP unit with a bulky branched alkyl chain have been synthesized for dye-sensitized solar cells. Due to a bulky branched alkyl chain being attached to the donor and DPP unit, both compounds obtain high Voc values. Under standard global AM 1.5 solar light conditions, the T1 based-device gives a high conversion efficiency of 8.24% with a Jsc of 15.72 mA cm−2, a Voc of 0.74 V and a FF of 0.71. These excellent performances make the donor dihydroindolo[2,3-b] carbazole and DPP unit promising candidates for further application in DSCs.

Small molecules based on diphenylamine and carbazole with large two-photon absorption cross sections and extraordinary AIEE properties

Two simple small molecules based on diphenylamine (T1) and carbazole (T2) have been synthesized for two-photon absorption materials. Both dyes exhibit extraordinary aggregation-induced emission enhancement (AIEE) properties and high corresponding quantum efficiencies of 11.5% and 16.0%. The value of the two-photon absorption cross-section for T1 is 1240 GM.

Small organic molecules based on oxazole/thiazole with excellent performances in green and red phosphorescent organic light-emitting diodes

Four pure organic molecules based on oxazole/thiazole were designed and characterized, and their relevant thermal, photophysical and electrochemical properties were fully investigated. These compounds (2a–2d) exhibited good thermal stabilities, with endothermic glass transitions over 120 °C, the largest of which was 2d with the endothermic glass transition of 145 °C. Four green devices, in which 2a–2d served as host materials, were fabricated and the device based on compound 2d exhibited the best performance with a maximum current efficiency of 50.7 cd A−1 and maximum power efficiency of 50.1 lm W−1. A red device based on 2d was also fabricated, which displayed a maximum current efficiency of 18.7 cd A−1 and maximum power efficiency of 17.3 lm W−1. The excellent performances of 2a–2d make them promising alternatives for efficient green and red devices.

Efficient blue fluorescent organic light-emitting diodes based on novel 9,10-diphenyl-anthracene derivatives

A series of novel 9,10-di(naphthalen-2-yl)anthracene (ADN) derivatives were designed and synthesized as blue fluorescent emissive materials by inducing diverse aromatic groups to the C-2 position of ADN. UV-Vis absorption, fluorescence emission spectroscopy and cyclic voltammetry (CV) were carried out to generally investigate the relationships between the physical properties and molecular structures. Moreover, four non-doped OLED devices adopting OCADN, FA3PADN, FA4PADN and OC4PADN as emitting materials were fabricated to study their electroluminescence (EL) performances. Among them, a device based on OCADN exhibited highly efficient sky-blue emission with a current efficiency of 2.25 cd A−1, power efficiency of 1.13 lm W−1 and CIE(x, y) coordinate of (0.16, 0.30) at 8 V. In addition, the device of OC4PADN showed efficient blue emission with a CIE(x, y) coordinate of (0.16, 0.14) at 8 V.

Pure hydrocarbon host materials based on spirofluorene with excellent performances for green phosphorescent light-emitting devices

Four pure hydrocarbon molecules based on spirofluorene were synthesized and their optoelectronic properties were investigated. These four compounds (1–4) exhibited excellent optoelectronic properties with good thermal stabilities, favorable optical energy bandgaps and triplet energies, compatible HOMO–LUMO energy levels and so on. Green phosphorescent organic light emitting devices (PHOLEDs) in which these four compounds served as host materials have been fabricated, and compound 1 demonstrated the optimal electroluminescence (EL) performance with a maximum current efficiency, maximum power efficiency and external quantum efficiency (EQE) of 31.5 cd A−1, 19.8 lm W−1 and 9.0%, respectively, which make it a promising candidate as a host material for PHOLEDs.