Peak current density and brightness from poly(p-phenylenevinylene) based light-emitting diodes

Transient electroluminescence of polymer light emitting diodes using electrical pulses

“…The ITO substrates were metallized with 100-nmthick aluminum strips ͑covered with an insulating layer of aluminum oxide͒ to reduce the resistance of the ITO sheet between the pulse generator and the active area, as reported in Ref. 13, and plasma etched to improve hole injection. 14 The active area of the diodes was 1 mm 2 and the residual resistance was less than 3 ⍀.…”

“…14 The active area of the diodes was 1 mm 2 and the residual resistance was less than 3 ⍀. The polymers used in the devices were: doped polyethylene dioxythiophene/polystyrene sulphonate ͑PEDOT:PSS͒ 15,16 ͑used as an anode layer͒; poly͑p-phenylenevinylene͒ ͑PPV͒; a copolymer of PPV consisting of conjugated PPV segments and nonconjugated acetylene-p-xylylene units ͑PPV copolymer͒ 13,15 ͑see Fig. 3͒, and poly͑di-octyl fluorene͒ ͑PFO͒ ͑see Fig.…”

“…For example, structures similar to device C, using the PPV copolymer, have previously produced peak brightnesses of 5 -20ϫ10 6 cd m Ϫ2 . 7,12,13 The PPV films were prepared by thermal conversion of the spun precursor polymer film in a dynamic vacuum of 10 Ϫ5 mbar with an inert base atmosphere. Several authors [17][18][19] have addressed the problem of PPV doping from the ITO during thermal conversion.…”

“…Short duration, low duty-cycle electrical pulses minimize the Joule heating effects [6][7][8][9][10][11] often associated with device failure in constant wave ͑CW͒ conditions, and allow access to higher field regimes (Ͼ10 7 V cm Ϫ1 ). 6,7 The high peak brightnesses (5 -20ϫ10 6 cd m Ϫ2 ), 12 peak current densities ͑kA cm Ϫ2 ͒, 7,13 and fast EL modulation achieved under pulsed operation also show promise for the future realization of polymer laser diodes and multiplexed displays.…”

Optical amplification of the cutoff mode in planar asymmetric polymer waveguides

“…2,3 In analogy with organic light-emitting diodes, one of the most obvious approaches to the electrical injection laser is to use a sandwich configuration in which the active material is a thin film between two electrodes. 4,5 Despite the fact that threshold current densities estimated from the excitation density required for optically pumped lasers have been exceeded in polymer diode structures by an order of magnitude, 6,7 electrically pumped laser emission has not been demonstrated. The losses in the electrically pumped devices are higher than in simple photopumped waveguides because of two additional loss mechanisms: losses introduced by the metal electrodes and charge-carrier ͑polaron͒-induced absorption.…”