Mohamad Izzat Azmer

Humidity sensor based on electrospun MEH-PPV:PVP microstructured composite

The present study demonstrates a solution-processed humidity sensor based on poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]:polyvinylpyrrolidone (MEH-PPV:PVP) organic microstructured composite thin film. The capacitive type humidity sensor has been fabricated in the surface type geometry of Al/MEH-PPV:PVP/Al, wherein organic composite (MEH-PPV:PVP) has been deposited onto the aluminium electrodes by electrospinning technique. The structural and morphological properties of organic thin film have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The humidity sensing properties of the sensor have been investigated at ∼1 volt AC operational bias, by measuring the capacitance as a function of a broad range (20–90%) of relative humidity (RH). The temperature and operational frequency dependency of the capacitance of the sensor has also been analyzed in detail. The proposed sensor exhibits high sensitivity (114 fF/% RH @ 100 Hz), small hysteresis (∼2% RH) and fast response (18 s and 8 s for adsorption and desorption processes, respectively). Compared with traditional spin-coated and drop-casted organic humidity sensors, the microstructure composite based sensor has demonstrated significantly improved sensing parameters, highlighting the unique advantages of the electrospinning process for humidity sensor fabrication. The possible humidity sensing mechanism of the proposed capacitive sensor has also been elaborated.

Improvement in the photovoltaic properties of hybrid solar cells by incorporating a QD-composite in the hole transport layer

A hybrid solar cell (HSC) based on a ZnSe and CdSe QDs-composite with improved conversion efficiency has been demonstrated. A novel approach of incorporating a QDs-composite (CdSe and ZnSe QDs simultaneously), in the poly(3,4-ethylenedioxythiophene)–poly(styrene sulfonate) (PEDOT : PSS) matrix by a simple cost effective solution processing technique, has been adopted. The combination of the QDs produced a 33% increase in the photo-conversion efficiency with a corresponding 67% enhancement in the fill factor (FF) when compared with the reference device. The micro-Raman analysis revealed effective strong coupling between both ZnSe and CdSe QDs, which promotes smooth charge transfer. This improved efficiency due to enhanced FF was achieved through interfacial engineering of the solution-processed hole transport layer, leading to facilitated charge transport and restrained bimolecular recombination. The present approach, outdoing the need of a cascaded layered structure, is compatible with the state-of-the-art hybrid solar cells, thus offering better throughput and a low cost manufacturing process for an improved-performance device.

Compositional engineering of VOPcPhO-TiO2 nano-composite to reduce the absolute threshold value of humidity sensors

This research work demonstrates compositional engineering of an organic-inorganic hybrid nano-composites for modifying absolute threshold of humidity sensors. Vanadyl-2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine (VOPcPhO), an organic semiconductor, doped with Titanium-dioxide nanoparticles (TiO2 NPs) has been employed to fabricate humidity sensors. The morphology of the VOPcPhO:TiO2 nano-composite films has been analyzed by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The sensors have been examined over a wide range of relative humidity i.e. 20-99% RH. The sensor with TiO2 (90nm) shows reduced sensitivity-threshold and improved linearity. The VOPcPhO:TiO2 (90nm) nano-composite film is comprised of uniformly distributed voids which makes the surface more favorable for adsorption of moisture content from environment. The VOPcPhO:TiO2 nano-composite based sensor demonstrates remarkable improvement in the sensing parameter when equated with VOPcPhO sensors.