Shanshan Zhao

Hydroxyphenyl-benzothiazole based full color organic emitting materials generated by facile molecular modification

Two sets of hydroxyphenyl-benzothiazole based compounds, which exhibited emission colors across the entire visible spectrum for both photoluminescence and electroluminescence, have been designed and synthesized.

Multicolor fluorescence and electroluminescence of an ICT-type organic solid tuned by modulating the accepting nature of the central core

A donor–acceptor–donor (D–A–D) molecule di(triphenylamine)-thiazolothiazole 1 has been employed in which the central Lewis-basic nitrogen atoms prompt it to be responsive to strong acids in both solution and solid states. As a result, the electron-accepting strength and intramolecular charge transfer (ICT) character can be controllably enhanced which make the emission band of 1 sequentially red-shift. The green luminescent solids (524 nm) can be smoothly transferred into yellow (576 nm), red (640 nm), and near infrared (739 nm) emissive states with a huge Δλem of 215 nm after being evaporated by HCl, TFA, and Lewis acid BBr3, respectively. Taking advantage of the smart sensitivity of 1 to acids, we prepared thermal-evaporated OLEDs based on the neutral and protonated species for the first time and achieved multicolor electroluminescence (EL) with very high brightness and moderate current efficiency. Thus, multicolor photoluminescence and thermally evaporated electroluminescence have been firstly realized based on a single organic chromophore, to the best of our knowledge.

Highly efficient phosphorescent OLEDs with host-independent and concentration-insensitive properties based on a bipolar iridium complex

A bipolar iridium complex, (ppy)2Ir(dipig), based on the ancillary ligand N,N′-diisopropyl-diisopropyl-guanidinate (dipig) with well-known cyclometalated (C^N) ligand ortho-(2-pyridyl)phenyl (ppy), is applicable in phosphorescent organic light-emitting diodes (PHOLEDs) as an efficient emitter, using easily available host materials and a simple device fabrication process. The corresponding PHOLEDs are dominated by an efficient direct-exciton-formation mechanism and show very high EL efficiency together with gratifying host- and doping-concentration-independent features. EL efficiency values of more than 93 lm W−1 for power efficiency (ηp) and 24% for external quantum efficiency (ηext) accompanied by little efficiency roll-off at high luminance are achieved in the (ppy)2Ir(dipig)-based devices by adopting the common materials 4,4′-bis(N-(1-naphthyl)-N-phenylamino)biphenyl (NPB) and 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) as the host, with rather random concentration ranges of 8–15 wt% and 15–30 wt%, respectively. To the best of our knowledge, these values are the highest efficiencies ever reported for yellow PHOLEDs, and are even comparable with the highest levels for PHOLEDs in the scientific literature. Moreover, the ηp and ηext values of the non-doped device can reach 70 lm W−1 and 18% respectively. They are almost two times higher than those of the most efficient reported PHOLEDs based on a neat emitting layer (EML).

Diboron-containing fluorophores with extended ladder-type π-conjugated skeletons

A series of ladder type π-conjugated diboron complexes 1-4 have been designed and synthesized by a very simple synthetic procedure. Single crystals of complex 3 were grown and the molecular structure determined by X-ray diffraction analysis demonstrated that this type of diboron ladder has a rather planar skeleton. All complexes possess very high melting points (275-383 °C) and decomposition temperatures (T(d5): 343-400 °C), indicative of their high thermal stabilities. The electrochemical and photophysical properties as well as theoretical calculations were investigated, suggesting the possibility of these boron complexes as efficient emitters in optoelectronics.

Oligo(3-hexylthiophene)-functionalized dicyano-ethylene substituted quinacridone derivatives: synthesis, characterizations and applications as acceptors in photovoltaic devices

A series of regioregular head-to-tail oligo(3-hexylthiophene)-functionalized dicyano-ethylene substituted quinacridone derivatives DCN-Tn-QA (n = 1–3) were designed and synthesized. These linear π-conjugated donor–acceptor–donor (D–A–D) molecules with different length of the oligothiophene chain have been achieved in good yields via iterative iodination and Suzuki cross-coupling reactions followed by Knoevenagel condensations. Their photophysical and electrochemical properties, as well as density functional theory (DFT) calculations, were systematically investigated. The compounds of DCN-Tn-QA (n = 1–3) with an intense absorption range from 350–750 nm, suitable LUMO levels at around −4.0 eV and considerable film formation properties, were suitable for application in organic solar cells (OSCs) as acceptors. The organic bulk heterojunction (BHJ) solar cell based on the blend film of P3HT/DCN-T2-QA (1 : 1, w/w) (P3HT = poly(3-hexylthiophene)) showed a power conversion efficiency (PCE) of 0.51% under the illumination of AM.1.5, 100 mW cm−2. Compared with P3HT/PCBM (PCBM = [6,6]-phenyl-C61-butyric acid methyl ester), the blend film of P3HT/DCN-T2-QA displayed a stronger response to the solar spectrum in the long wavelength range from 665–750 nm.

Theoretical study on the charge transport property of Pt(CNtBu)2(CN)2 nanowires induced by Pt⋯Pt interactions

To deeply understand the charge-transporting nature of Pt(CN(t)Bu)(2)(CN)(2) nanowires induced by intermolecular Pt···Pt interactions, calculations based on first-principle band structure and Marcus theory have been performed. The calculated bandwidths of the valence band, conducting band, and the effective masses of hole and electron are almost equal. This suggests that this complex has ambipolar transport characteristics, in agreement with experimental results. Density of states analysis revealed that the hole transport resulted mainly from the Pt···Pt interactions, while the electron transport was derived mainly from the CN groups. The character of the frontier molecular orbitals, reorganization energies and transfer integrals in different directions also supports the calculated first-principle band structure. Moreover, an investigation into the intermolecular interaction energy of neighbors revealed that there is a remarkable relationship between the intermolecular interaction energy and the transfer integral.