MEH-PPV/Alq₃-based bulk heterojunction photodetector

In this paper, we present the effect of varied illumination levels on the electrical properties of the organic blend bulk heterojuction (BHJ) photodiode. To prepare the BHJ blend, poly(2-methoxy-5(2’-ethylhexyloxy) phenylenevinylene (MEH-PPV) and aluminum-tris-(8-hydroxyquinoline) (Alq₃) are used as donor and acceptor materials, respectively. In order to fabricate the photodiode, a 40-nm thick film of poly(3, 4-ethylendioxythiophene):poly(styrensulfonate) (PEDOT:PSS) is primarily deposited on a cleaned ITO coated glass substrate by spin coating technique. The organic photosensitive blend is later spun coated on the PEDOT:PSS layer, followed by the lithium fluoride (LiF) and aluminium (Al) thin films deposition by thermal evaporation. The optical properties of the MEH-PPV:Alq₃ blend thin films are investigated using photoluminescence (PL) and UV-Vis spectroscopy. The photodiode shows good photo-current response as a function of variable illumination levels. The responsivity value ～ 8 mA/W at 3 V is found and the ratio of photo-current to dark current (I_Ph/I_Dark) is found to be 1.24.