Organic Multiple Quantum Wells Research Articles

Observation and numerical analysis of quantum subband energies from photoluminescence spectra of organic multiple-quantum wells

The optical properties of organic light-emitting diodes (OLEDs) containing multiple-quantum wells have been studied. Photoluminescence and electroluminescence spectra clearly reveal a blue-shift with narrowing quantum wells (QWs). This indicates that subband energies are created in the organic QWs due to quantum size effect. Numerical analysis was performed to determine subband energies and effective masses of electrons. These results demonstrate that wavelength of OLEDs can be designed on the basis of quantum size effect.

Tuning of chromaticity in organic multiple-quantum well white light emitting devices

We fabricate organic multiple-quantum wells structure (MQWs) white light-emitting diodes (LEDs), in which blue fluorescent phenylpyridine beryllium (BePP 2), orange fluorescent rubrene doped green fluorescent aluminum complex (Alq 3) act as MQWs light-emitting layers between potential barriers triphenyldiamine derivative (TPD). Excitons are confined in different MQWs light-emitting layers due to higher bandgap E g of TPD. The Commission Internationale de l'Eclairage (CIE) coordinates of the emitted light are tuned by changing the well number ratio of BePP 2 to Alq:rubrene. The organic MQWs white LEDs with three BePP 2 wells show excellent optical and electrical performance. The CIE coordinates of the emitted light vary from (0.42, 0.38) to (0.34, 0.34) when forward voltages change from 7 to 13 V, which are just near to the white-light equi-energy point (0.33, 0.33). The brightness and luminous efficiency are 611 cd/m 2 and 0.34 lm/W at 12 V, respectively.

Chromaticity-tunable white light emission from organic multiple-quantum-well structure

Organic multiple quantum wells (MQWs) white light emitting devices are fabricated in which blue fluorescent dye, a trimer of N-anylbenzimidazole (TPBI) and orange fluorescent rubrene doped tris (8-hydroxyquinoline) Aluminum act as quantum-well light emitting layers between triphenyldiamine derivative (TPD) potential barrier layers, and aluminium complex (Alq) act as an electron transporter and green emitter. The injected carriers are confined in different quantum wells and Alq layer. The white light emission comes from a combination of photons generated in different light emitting layers. The Commission Internationale de l' Eclairage (CIE) coordinates of the emitted light are tuned by increasing the number of TPBI wells due to its low fluorescent efficiency compared with rubrene.

Determination of the parallel and perpendicular intermolecular tunnelling rates in two Langmuir-Blodgett quantum well systems

The first experimental determination of the anisotropy of the electron transfer rate in two Langmuir-Blodgett insulator multilayer systems is presented. A key feature of these two multilayer systems is the presence of the planar conjugated phthalocyanine ring. The first system is composed of tetra-tertiary-butyl phthalocyanine monosulphonic acid. In it the ring planes are approximately normal to the layer plane. The second system is composed of the two-ring phthalocyanine HOSiPcOSiPcOSI( nC 6H 13) 3. In it the rings lie in the layer plane. The anisotropy of the systems is determined from a model of the recombination rate, at high density, of photoelectrons and photoholes on the same layer. The ratio of the intralayer to interlayer transfer rates between adjacent rings is found to be 1500 and 570 respectively. Coupled with a previous determination of the interlayer transfer time of 1.6 and 0.30 ns, the intralayer transfer times are then determined as 1.07 and 0.56 ps respectively. The in-plane mobilities can then be determined as 0.34 and 1.2 cm 2 s −1 V −1 respectively. The results justify regarding these systems as organic multiple-quantum wells.

Determination of anisotropic electron transport properties of two Langmuir-Blodgett organic multiple quantum wells

The first experimental determination of the anisotropy of the electron transfer rate in two- Langmuir-Blodgett insulator multilayer systems is presented. A key feature of these two multilayer systems is the presence of the planar-conjugated phthalocyanine ring. The first system is composed of tetra-tertiary-butyl phthalocyanine monosulphonic acid. In it the ring planes are approximately normal to the layer plane. The second system is composed of the two-ring phthalocyanine, HOSiPcOSiPcOSi(n-C 6H 13) 3. In it the rings lie in the layer plane. The anisotropy of the systems is determined from a model of the recombination rate, at high density, of photoelectrons and photoholes on the same layer. The ratio of the intralayer to interlayer transfer rate between adjacent rings is found to be 1500 and 570 respectively. Coupled with a previous determination of the interlayer transfer time of 1.6 and 0.15 ns, the intralayer transfer times are then determined as 1.07 and 0.28 ps respectively. The in-plane mobilities can then be determined as 0.34 and 2.4 cm 2 s -1 V -1 respectively. The results justify regarding these systems as organic multiple quantum wells.

Optical nonlinearities in crystalline organic multiple quantum wells.

A study of the linear and nonlinear optical behavior of recently realized crystalline organic semiconductor quantum wells is reported. Using the Davydov Hamiltonian, we find analytical solutions for the optical response function, and we predict the existence of intrinsic optical bistability and two-beam-coupling energy transfer in these materials.