The electroluminescent and photodiode device made of a polymer blend

Organic thin film diodes made by a polymer blend of poly[2-methoxy,5-(2′-ethyl-hexoxy)-1,4-phenylenevinylene] (MEH-PPV) and poly[1,3-propanedioxy-1,4-phenylene-1,2-ethenylene-(2,5-bis(trimethylsilyl)-1,4- phenylene)-1,2-ethenylene-1,4-phenylene] (called the B-polymer) are investigated. The device of sandwich configuration indium-tin oxide (ITO)/polymer-blend/Al emits orange light under forward bias at +10 V and the same device acts as a photodiode under reverse bias. To investigate the photodiode characteristics, the 516 nm wavelength with 9.5 mW/cm² intensity of light is illuminated through the Al contact side of the device. The I-V characteristic measurement shows the short circuit current and the open circuit voltage of -1.22×10^-9 A/cm² and 0.8 V, respectively. The ratio of the photocurrent to the dark current is about 4×10² at -2.5 V reverse bias. The maximum d.c. sensitivity is 1.35×10^-5 A/W at -7 V reverse bias voltage with 16 mW/cm² intensity of the incident light. The results indicate the possibility of making photosensors using this device.