An organic p-i-n homojunction as ultra violet light emitting diode and visible-blind photodiode in one

Organic p-i-n homojunctions that function both as ultra violet light emitting diode (peak wavelengths around 375 nm and 415 nm) and visible-blind photodiode are reported. They are considered as the organic counterpart to what has exclusively been known from inorganic semiconductors, as yet. The diodes are based on the ambipolar material 4,4-Bis(carbazol-9-yl)-biphenyl (CBP) which is p- and n-type doped adjacent to the electrodes. We study the emission characteristics of the p-i-n homojunction for varied doping concentrations and subsequently focus on its characteristics as photodiode. A superlinear relation of photocurrent and incident light intensity is found and attributed to an intensity-dependent photoconductivity. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3617427]