Infrared proximity sensor using organic light-emitting diode with quantum dots converter

Abstract: An efficient visible-to-infrared conversion film is made by blending CdTe quantum dots (CdTe QDs) of 12nm diameter in a polyvinylpyrrolidone 360 (PVP 360) polymer matrix cast by water solution. The solid-state photoluminescence quantum efficiency exceeds 10% with emission peak at 810nm. Strong 810 emission is obtained by combining the quantum dot film and a green polyfluorene light-emitting diode. Color filter is used to remove residual light below 780nm to make it entirely invisible. Infrared photo-detector is made by blending poly[5-(5-(2,5-bis(decyloxy)-4-methylphenyl)thiophen-2-yl)-2,3-bis(4-(2-ethylhexyloxy)phenyl)-7-(5-methylthiophen-2-yl)thieno[3,4-b]pyrazine] (PBDOTTP) with band-gap 1.2eV and (6,6)-phenyl-C61-butyric acid methyl ester (PCBM). The pixel contains one PD surrounded by four PLED on its four sides. The active areas of the five devices are all 1cm by 1cm and they are on the same plane. Infrared proximity sensor with photo-current over 300nA at 10cm object distance is achieved by detecting the reflected infrared signal. [Copyright &y& Elsevier]