[en] In this research, we report a bulk heterojunction (BHJ) solar cell consisting of a ternary blend system. Poly(3-hexylthiophene) P3HT is used as a donor and [6,6]-phenyl C61-butyric acid methylester (PCBM) plays the role of acceptor whereas vanadyl 2,9,16,23-tetraphenoxy-29H, 31H-phthalocyanine (VOPcPhO) is selected as an ambipolar transport material. The materials are selected and assembled in such a fashion that the generated charge carriers could efficiently be transported rightwards within the blend. The organic BHJ solar cells consist of ITO/PEDOT:PSS/ternary BHJ blend/Al structure. The power conversion efficiencies of the ITO/ PEDOT:PSS/P3HT:PCBM/Al and ITO/PEDOT:PSS/ P3HT:PCBM:VOPcPhO/Al solar cells are found to be 2.3% and 3.4%, respectively. (paper)

[en] In this paper, the fabrication and investigation of flexible impedance and capacitive tensile load sensors based on carbon nanotube (CNT) composite are reported. On thin rubber substrates, CNTs are deposited from suspension in water and pressed at elevated temperature. It is found that the fabricated load cells are highly sensitive to the applied mechanical force with good repeatability. The increase in impedance of the cells is observed to be 2.0 times while the decrease in the capacitance is found to be 2.1 times as applied force increases up to 0.3 N. The average impedance and capacitive sensitivity of the cell are equal to 3.4 N"−"1 and 1.8 N"−"1, respectively. Experimental results are compared with the simulated values, and they show that they are in reasonable agreement with each other. (paper)

[en] A novel surface-type nonvolatile electric memory elements based on organic semiconductors CuPc and H_2Pc are fabricated by vacuum deposition of the CuPc and H_2Pc films on preliminary deposited metallic (Ag and Cu) electrodes. The gap between Ag and Cu electrodes is 30–40 μm. For the current–voltage (I–V) characteristics the memory effect, switching effect, and negative differential resistance regions are observed. The switching mechanism is attributed to the electric-field-induced charge transfer. As a result the device switches from a low to a high-conductivity state and then back to a low conductivity state if the opposite polarity voltage is applied. The ratio of resistance at the high resistance state to that at the low resistance state is equal to 120–150. Under the switching condition, the electric current increases ∼ 80–100 times. A comparison between the forward and reverse I–V characteristics shows the presence of rectifying behavior. (paper)

[en] The current study provides an insight into the thermal stability of perovskite solar cells (PSCs) and the factors causing their degradation. To this end, a systematic stability study was carried out on n-i-p type perovskite solar cells involving mesoporous TiO₂ layer. The samples were subjected to varying moisture and thermal conditions under light soaking while being exposed to long-term indoor (5000 h) and outdoor (75 h) harsh environmental conditions (i.e. 30%–80% RH and 40 °C–70 °C). To identify performance and morphological changes of PSCs after exposure to thermal stress, advanced characterization techniques including impedance spectroscopy, scanning electron microscopy and glow discharge optical emission spectrometry along with I–V characteristics were used. The un-encapsulated samples exposed to high thermal stress (40–70 °C) show degradation in their efficiency more than 40% within the 75 h of thermal stress. In contrast, the samples that were kept at room temperature were found to be very stable over 5000 h.

[en] We report the effect of microwaves sintering on the crystal domain and electrical properties of TiO₂ nanoparticles. Commercially available TiO₂ nanoparticles of 25 nm size were coated on ITO (indium tin oxide) substrates, which were then sintered at 450 °C employing microwave and conventional sintering approaches. The structural properties of the sintered coatings were examined using atomic force microscopy (AFM), scanning electron microscope (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS), whereas the charge transfer properties were investigated using electrochemical impedance spectroscopy (EIS). Structural analysis reveals that the microwave sintering of TiO₂-coated substrates results in the formation of more ordered crystal structure as compared to the conventionally sintered samples. Nyquist plots demonstrate the improved charge transfer characteristics of TiO₂ nanoparticles in microwave-sintered layers. Also, the application of the microwave-sintered TiO₂-coated ITO substrates as photoanode in dye-sensitized solar cells (DSSCs) confirms superior electrical properties compared to conventionally sintered samples.

[en] Highlights: • VOPcPhO:P3HT micro-structures with nano-porous surface morphology have been formed. • Multidimensional structures have been formed by electro-spraying technique. • The electro-sprayed films are very promising for the humidity sensors. - Abstract: In this paper, composite micro-structures of Vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine) (VOPcPhO) and Poly (3-hexylthiophene-2,5-diyl) (P3HT) complex with nano-porous surface morphology have been developed by electro-spraying technique. The structural and morphological characteristics of the VOPcPhO:P3HT composite films have been studied by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The multidimensional VOPcPhO:P3HT micro-structures formed by electro-spraying with nano-porous surface morphology are very promising for the humidity sensors due to the pore sizes in the range of micro to nano-meters scale. The performance of the VOPcPhO:P3HT electro-sprayed sensor is superior in term of sensitivity, hysteresis and response/recovery times as compared to the spin-coated one. The electro-sprayed humidity sensor exhibits ∼3 times and 0.19 times lower hysteresis in capacitive and resistive mode, respectively, as compared to the spin-coated humidity sensor.

[en] Highlights: • We study the effect of different sintering methods on the TE properties of Bi₂Te₃. • The samples sintered using conventional, microwave, and tube sintering techniques. • Overall low thermal conductivity was observed at 250 °C in all sintering methods. • Also, broadband dielectric spectroscopy was done to find the dielectric properties. -- Abstract: This work intends to investigate the optimum sintering method and temperature that can improve the efficiency of bismuth telluride cold compact pellets, for the thermoelectric applications. Different p-type and n-type bismuth telluride cold compact pellets were treated using three different sintering techniques and conditions: pressure less (conventional), microwave, and tube (using argon environment) at temperatures 250 °C, 300 °C, 350 °C, and 400 °C. The structural, microscopic, electron transport, thermal, and dielectric properties of the pristine and sintered samples were examined. Broadband dielectric spectroscopy was performed to extract a detailed picture of the dielectric properties of the samples. Even though each type of sintering had its own merits and demerits, the optimum conditions for enhanced electric and thermal features were found in microwave furnace followed by tube and conventional. Low thermal conductivity of 0.4 W/m/K was observed in the samples sintered at 250 °C while the increase in sintering temperature from 250 °C to 300 °C improved the crystallinity of the material. Moreover, the crystal structure of the bismuth telluride altered with the occurrence of higher oxidation leading to the formation of high bismuth telluride oxide phases at sintering temperatures above 300 °C, more dominantly in the n-type samples.

[en] In the present work, spectroscopic features and sensitivity of poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) and vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine (VOPcPhO) based photodetector have been improved by employing cadmium selenide quantum dots (CdSe QDs). The incorporation of CdSe QDs has heightened the optical absorption, particularly in the range of 400–560 nm. The MEH-PPV:VOPcPhO:CdSe based hybrid photodetector (PD) has been investigated under the influence of illumination levels varying from 0–140 mW/cm². The PD fabricated with CdSe QDs is found to be 3.2 times faster in response time and 2 times quicker in the recovery time as compared to the PD without CdSe QDs.