A MEHPPV/VOPcPhO composite based diode as a photodetector

• A solution-processed visible photodetector using an organic D/A semiconductor materials.
• PL study shows the quenching phenomena in the D/A blend.
• Extended photosensitivity and light harvesting range have been obtained.

We demonstrate a solution-processed visible wavelength photodetector using an organic semiconductor blend of poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene] (MEHPPV) and vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine (VOPcPhO) to function as the donor (D) and the acceptor (A) materials, respectively. The photodetector was fabricated in the vertical geometry of ITO/PEDOT:PSS/MEHPPV:VOPcPhO/Al and the effects of varying levels of illumination on photodetector's electrical parameters were studied. Aqueous solution of PEDOT:PSS [poly(3,4-ethylendioxythiophene):poly(styrensulfonate)] and solution of D/A materials in chloroform were sequentially spun coated on the cleaned ITO coated glass substrate. Aluminum (Al) cathodes were later thermally deposited on top of the active layer through a shadow mask with circular openings of 2 mm2. The photoluminescence (PL) spectra of D/A blends have been studied to optimize the volumetric ratio of the blend. The UV–vis spectrum shows that organic blend exhibits a broad absorption over almost the whole visible range. By virtue of its enhanced visible light absorbing capability, the organic blend has been utilized to fabricate the photodetector. The sensor showed an efficient photo-current response as a function of varied illumination levels. Further the detector revealed prompt reversible electrical changes versus variation in illumination levels. Since this proposed photodetector can harvest incident photons over almost the whole visible range and is inexpensive to manufacture, therefore, it has a great potential for practical applications.