White light electroluminescence from PSi devices capped with poly(thiophene)(s) as top contact

For the first time, electrochemically deposited poly(3-methylthiophene) and chemically produced poly(3-methylthiophene) and poly(3-phenoxymethylthiophene) have been employed as top electrical contact on porous silicon light-emitting devices. The polymer-capped devices emitted white light as opposed to the uncapped devices, which emitted orange colour. The polymer-capped devices show much higher rectification ratio (up to 1 X 10(5)) as opposed to 1 X 10(3) for the uncapped devices at +/- 10 V. The polymer-capped devices show 10(3)-10(4)-fold improvement in the luminous efficiency over the uncapped devices. Electrochemically deposited poly(3-methylthiophene) top contacts give a luminous efficiency of 8 x 10(-5) lm W-1 as opposed to 3 X 10(-9) lm W-1 obtained from uncapped devices. All the devices were found to fit the space charge limited current model. (C) 2000 Elsevier Science S.A. All rights reserved.