A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

Synthesis of Light-Emitting Conjugated Polymers for Applications in Electroluminescent Devices

An improved experimental determination of external photoluminescence quantum efficiency

This article provides a review about electroluminescence from organic materials and deals in detail with organic light-emitting diodes (OLEDs), light-emitting electro-chemical cells (LECs) and electrogenerated chemilumi-nescence (ECL) reflecting different electrooptical appli-cations of conjugated materials. It is written from an organic chemist's point of view and pays particular attention to the development of organic materials involved in corresponding devices. In recent years a substantial amount of both academic and industrial research has been directed to organic electroluminescence in an effort to improve the processability and tunability of organic materials and the longevity of OLEDs and LECs. On the eve of the commercialization of organic electrolumi-nescence this review provides an overview of lifetimes and efficiencies attained and reflects materials and device concepts developed over the last decade. In this context electrogenerated chemiluminescence is discussed with respect to its importance as a versatile tool to simulate the fundamental electrochemical processes in OLEDs.

The electroluminescence of organic materials

http://nathan.instras.com/documentDB/paper-69.pdf

Porous silicon: a quantum sponge structure for silicon based optoelectronics

The photosensitivity of semiconducting polymers can be enhanced by blending donor and acceptor polymers to optimize photoinduced charge separation. We describe a novel phase‐separated polymer blend (composite) made with poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐1,4‐phenylene vinylene], MEH‐PPV, as donor and cyano‐PPV, CN‐PPV, as acceptor. The photoluminescence and electroluminescence of both component polymers are quenched in the blend, indicative of rapid and efficient separation of photogenerated electron‐hole pairs with electrons on the acceptor and holes on the donor. Diodes made with such a composite semiconducting polymer as the photosensitive medium show promising photovoltaic characteristics with carrier collection efficiency of 5% electrons/photon and energy conversion efficiency of 0.9%, ∼20 times larger than in diodes made with pure MEH‐PPV and ∼100 times larger than in diodes made with CN‐PPV. The photosensitivity and the quantum yield increase with reverse bias voltage, to 0.3 A/W and 80% electrons/photon respectively at −10 V, comparable to results obtained from photodiodes made with inorganic semiconductors.

Charge separation and photovoltaic conversion in polymer composites with internal donor/acceptor heterojunctions

Photo- and electroluminescence efficiency in poly(dialkoxy-p-phenylenevinylene)

Using photoluminescence decay measurements the radiative lifetime of porous silicon is investigated between liquid helium and room temperature. The radiative recombination mechanism in porous silicon is in essence the same as in bulk silicon, viz. a phonon mediated indirect transition. The functional dependence of the lifetime on photon energy reveals the confinement character of the recombination carriers. The high external photoluminescence efficiency is well explained by the reduction of nonradiative recombination owing to low mobility, to low dimensionality, and to the extreme low surface recombination rate, and is further enhanced by the relatively small refractive index.

Temperature dependence of the radiative lifetime in porous silicon

https://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1056&context=eeng_fac

Electroluminescence and photoluminescence efficiency of poly(p-phenylenevinylene) derivatives

An illumination system has an active layer which includes an electroluminescent material, the active layer being located between an optically transparent electrode layer and a reflective electrode layer. A reflective polarizer is present at a side of the transparent electrode layer facing away from the active layer. A sub-beam incident on the polarizer and having an unwanted polarization is reflected back to the active layer, where it is again partially depolarized to recover a component having the desired state of polarization. The invention also relates to a flat-panel picture display device which includes such an illumination system.

/pdf/electroluminescent-illumination-system-518q6txwfb.pdf

Electroluminescent illumination system

The current injection into metal/porous Si/bulk Si diodes is investigated by transport and photoresponse measurements. Under low forward bias, the diode current is determined by the space charge region at the porous Si/bulk Si interface. The activation energy of the photovoltage shows that holes are injected into porous Si states which have little quantum confinement. This is discussed in terms of the confinement model for porous Si photoluminescence.

A. H. J. Venhuizen

Papers

Photo- and electroluminescence efficiency in poly(dialkoxy-p-phenylenevinylene)

Temperature dependence of the radiative lifetime in porous silicon

Electroluminescence and photoluminescence efficiency of poly(p-phenylenevinylene) derivatives

Electroluminescent illumination system

Behavior of a rectifying junction at the interface between porous silicon and its substrate