In this paper, we present the effect of varying humidity levels on the electrical parameters and the multi frequency response of the electrical parameters of an organic-inorganic composite (PEPC+NiPc+Cu₂O)-based humidity sensor. Silver thin films (thickness ~200 nm) were primarily deposited on plasma cleaned glass substrates by the physical vapor deposition (PVD) technique. A pair of rectangular silver electrodes was formed by patterning silver film through standard optical lithography technique. An active layer of organic-inorganic composite for humidity sensing was later spun coated to cover the separation between the silver electrodes. The electrical characterization of the sensor was performed as a function of relative humidity levels and frequency of the AC input signal. The sensor showed reversible changes in its capacitance with variations in humidity level. The maximum sensitivity ~31.6 pF/%RH at 100 Hz in capacitive mode of operation has been attained. The aim of this study was to increase the sensitivity of the previously reported humidity sensors using PEPC and NiPc, which has been successfully achieved.

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 (IPh/IDark) is found to be 1.24.

We present a ternary blend-based bulk heterojunction ITO/PEDOT:PSS/PFO-DBT: MEH-PPV:PC₇₁BM/LiF/Al photodetector. Enhanced optical absorption range of the active film has been achieved by blending two donor components viz. poly[2,7-(9,9-di-octyl-fluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PFO-DBT) and poly(2-methoxy-5(2'-ethylhexyloxy) phenylenevinylene (MEH-PPV) along with an acceptor component, i.e., (6,6)-phenyl-C₇₁ hexnoic acid methyl ester. The dependency of the generation rate of free charge carriers in the organic photodetector (OPD) on varied incident optical power density was investigated as a function of different reverse biasing voltages. The photocurrent showed significant enhancement as the intensity of light impinging on active area of OPD is increased. The ratio of I_light to I_dark of fabricated device at −3 V was ~3.5 × 10⁴. The dynamic behaviour of the OPD under on/off switching irradiation revealed that sensor exhibits quick response and recovery time of ∼800 ms and 500 ms, respectively. Besides reliability and repeatability in the photoresponse characteristics, the cost-effective and eco-friendly fabrication is the added benefit of the fabricated OPD.

Bulk heterojunction organic solar cells have been fabricated based on PCDTBT:PC71BM blend in three different procedures involving thermal annealing treatment. The first solar cell has been fabricated by spin coating PEDOT:PSS solution onto ITO-coated glass substrate in order to form 40nm buffer layer and followed by the formation of 70nm PCDTBT:PC71BM active layer. Without undergoing any treatment, an aluminium layer of about 100nm thick has been formed on top of this active layer by means of thermal evaporation in vacuum condition. For the second solar cell fabrication, the active layer has been thermally treated at 70 oC for 30min before the deposition of Al top contact. And for the third solar cell, the fabrication has been done exactly as previous but having additional thermal treatment at 70 oC for 30min after the deposition of Al top contact. All the devices have been characterized by I-V measurement in dark and under light illumination in ambient condition. The first solar cell has shown the highest efficiency up to 9.3%, followed by the second solar cells that achieved 4.8% efficiency and the third solar cell with 2.3% efficiency. However, it is observed that the stability of first solar cells is drastically dropped in a day indicates that the solar cell had experienced a serious instability. The second solar cell shows an improve stability by having less reduces in it efficiency. While the third solar cell showing even better stability than the second one by giving an enhanced stability. It is observed that, without thermal annealing, highest efficiency could be achieved but has poor stability. While by having twice thermal annealing, the solar cell will have lower efficiency but better stability

π-conjugated organic semiconductors have long been used as either holes or electrons transport materials. Recently, ambipolar charge carrier transport in these materials have been reported in many investigations. In this paper, we report on the basis of experimental results that the organic semiconductor (donor/acceptor) materials can be as good electrons transporters as these materials are holes transporters. In our study, the solution-processed unipolar diodes based on organic materials P3HT, VOPCPhO, and their blends with PCBM have been fabricated. The I–V characteristics of these diodes have been analyzed in the space-charge-limited current regime. The values of the electron and hole mobilities for the materials were found in the range of 10⁻⁴–10⁻⁵ cm²/Vs.