Several substituted phenanthrolines (L = pyrazino[2,3‐f][1,10]phenanthroline (PyPhen), 2‐methylpyrazino[2,3‐f][1,10]phenanthroline (MPP), dipyrido[3,2‐a:2′,3′‐c]phenazine (DPPz), 11‐methyldipyrido[3,2‐a:2′,3′‐c]phenazine (MDPz), 11,12‐dimethyldipyrido[3,2‐a:2′,3′‐c]phenazine (DDPz), and benzo[i]dipyrido[3,2‐a:2,3‐c]phenazine (BDPz)) were successfully prepared and europium complexes Eu(TTA)3L (Eu‐L) based on these ligands were synthesized from EuCl3, 2‐thenoyltrifluoroacetone (TTA) and L in good yields. Irradiation at the absorption band between 320–390 nm of all these europium complexes, except Eu‐BDPz, in solution or in the solid state leads to the emission of a sharp red band at ∼ 612 nm, a characteristic Eu3+ emission due to the transition 5D0 → 7F2. No emission from the ligands was found. The result indicates that complete energy transfer from the ligand to the center Eu3+ ion occurs for these europium complexes. In contrast, the photoluminescence spectrum of Eu‐BDPz exhibits a strong emission at around 550 nm from the coordinated BDPz ligand and a weak emission at 612 nm from the central europium ion. Incomplete energy transfer from the ligand to the central Eu3+ ion was observed for the first time. Several electroluminescent devices (A–I) using Eu‐PyPhen, Eu‐MPP, Eu‐DPPz, and Eu‐DDPz as dopant emitters with the device configuration: TPD or NPB (50 nm)/Eu:CBP (1.7–7 %, 30 nm)/BCP (20–30 nm)/Alq (25–35 nm) (where TPD: 4,4′‐bis[N‐(p‐tolyl)‐N‐phenylamino]biphenyl; NPB: 4,4′‐bis[1‐naphthylphenylamino]biphenyl; CBP: 4,4′‐N,N′‐dicarbazole biphenyl; BCP: 2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline; Alq: tris[8‐hydroxyquinoline]aluminum) were fabricated. Some of these devices emit saturated red light and are the only europium complex‐based devices that show a brightness of more than 1000 cd m–2.

We present results of picosecond photoinduced absorption (PA) and time-resolved photoluminescence studies on solid and solution forms of poly(p-pyridyl vinylene). The nearly identical PA response of all forms of the polymer reflects the generation of the same primary photoexcitation, a Couloumbically bound intrachain singlet exciton, and the absence of exotic species such as interchain excimers. The time dependence of the PA points to direct intersystem crossing as the origin of triplet excitons, ruling out generation of free carriers as a precursor to exciton formation. PACS numbers: 72.80.Le, 71.35.Cc, 78.47.+p The suggestion that Coulombically bound excitons are the primary photoexcitations of conjugated polymers has resulted in much debate and controversy, particularly in relation to arylene-vinylene-based polymers such as poly(p-phenylene vinylene) (PPV) [1-3]. Many different models have been proposed as to the nature of these excitons: Pakbaz et al. suggest that the Coulomb binding energy of the exciton is negligible, so that the primary photoexcitations of PPV are free carriers that later selflocalize to form "polaron-excitons" bound exclusively by the electron-phonon interaction [4]. Other authors suggest a Frenkel or Wannierlike nature for the exciton, with a binding energy of several hundred meV [5][6][7]. Still others suggest strongly correlated excitons, with Coulomb binding energies on the order of 1 eV [8][9][10][11]. The issue of the nature of the exciton is of particular relevance because excitonic emission is thought to give the strong photoluminescence (PL) and electroluminescence seen in many conjugated polymers [12].The debate over the primary photoexcitations in PPV and related systems has led to numerous ultrafast spectroscopic studies, again the interpretation of which has proven controversial. PPV shows strong, quasiinstantaneous photoinduced absorption (PA) at energies of ϳ1.5 eV [9,[13][14][15][16][17]. Leng et al. [9] suggest that the strong PA arises from a transition from the lowest exciton state (S 1 ), and cite as evidence a correlation between the time dynamics of the PL and the time derivative of the PA (PL ϳ d͓PA͔͞dt) at early times (,400 ps). Such a correlation might be expected if the PA were due entirely to singlet excitons, as PA(t) is proportional to exciton density and PL(t) to the rate of change of exciton density due to radiative recombination. They ascribe the discrepancy between PA and PL at later times to the trapping of excitons at defects [15]. On the other hand, Hsu et al. [16] take the discrepancy between PA and PL as evidence for photogeneration of a species distinct from the singlet exciton: namely, "polaron pairs," or interchain excimers [18]. Yan et al. [17], citing an apparent competition between the PA and stimulated emission (SE), suggest that the quantum efficiency for polaron-pair generation is as high as 90%.In this Letter, we address the nature of the PA in arylenevinylene polymers via time-resolved studies on poly(ppyridyl vinylene) (PPyV), the pyri...

The characteristics of OLED backplanes including the intrinsic properties of a-Si TFTs and LTPS TFTs will be reviewed. While LTPS TFTs reveal satisfactory stability in AMOLED-display applications, a-Si AMOLEDs show better uniformity and are capable of driving OLEDs. However, the stability of a-Si TFTs under long-term operation is still unacceptable and remains to be the key issue constraining the commercialization of a-Si TFT AMOLEDs.

Abstract— The bottlenecks in achieving high resolution for active‐matrix OLED (AMOLED) displays based on currently available manufacturing processes were evaluated and compared. The use of a shadow mask has proven to be viable for mass production, but the fabrication of high‐precision shadow masks becomes very difficult when the resolution exceeds 180 ppi. The latest breakthrough in increasing display resolution is presented. Without an increase in cost, the limitations of the conventional shadow‐mask process using novel subpixel designs have been successfully overcome. A high resolution reaching of 270 ppi has been successfully demonstrated on a 3‐in. VGA‐format AMOLED display, fabricated by using a shadow mask with a much lower resolution of 135 ppi. This innovative pixel design opens up the possibilities of manufacturing high‐resolution displays using a relatively low‐resolution shadow mask.

A new approach has been developed to improve AMOLED's image quality. Fast Transient Compensation Mechanism (FTCM) provides a good ability on Vth compensation, based on sub‐pixel circuit structure consisting of 6 TFTs and 1 capacitor. Furthermore, the P‐type GOA in AMOLED panel is designed for pixel driving and enhances displaying quality at low gray scale.