Abu Farzan Mitul

Interfacial Study To Suppress Charge Carrier Recombination for High Efficiency Perovskite Solar Cells.

We report effects of an interface between TiO2-perovskite and grain-grain boundaries of perovskite films prepared by single step and sequential deposited technique using different annealing times at optimum temperature. Nanoscale kelvin probe force microscopy (KPFM) measurement shows that charge transport in a perovskite solar cell critically depends upon the annealing conditions. The KPFM results of single step and sequential deposited films show that the increase in potential barrier suppresses the back-recombination between electrons in TiO2 and holes in perovskite. Spatial mapping of the surface potential within perovskite film exhibits higher positive potential at grain boundaries compared to the surface of the grains. The average grain boundary potential of 300-400 mV is obtained upon annealing for sequentially deposited films. X-ray diffraction (XRD) spectra indicate the formation of a PbI2 phase upon annealing which suppresses the recombination. Transient analysis exhibits that the optimum device has higher carrier lifetime and short carrier transport time among all devices. An optimum grain boundary potential and proper band alignment between the TiO2 electron transport layer (ETL) and the perovskite absorber layer help to increase the overall device performance.

Benzothiadiazole-based polymer for single and double junction solar cells with high open circuit voltage.

Single and double junction solar cells with high open circuit voltage were fabricated using poly{thiophene-2,5-diyl-alt-[5,6-bis(dodecyloxy)benzo[c][1,2,5]thiadiazole]-4,7-diyl} (PBT-T1) blended with fullerene derivatives in different weight ratios. The role of fullerene loading on structural and morphological changes was investigated using atomic force microscopy (AFM) and X-ray diffraction (XRD). The XRD and AFM measurements showed that a higher fullerene mixing ratio led to breaking of inter-chain packing and hence resulted in smaller disordered polymer domains. When the PBT-T1:PC60BM weight ratio was 1 : 1, the polymer retained its structural order; however, large aggregated domains formed, leading to poor device performance due to low fill factor and short circuit current density. When the ratio was increased to 1 : 2 and then 1 : 3, smaller amorphous domains were observed, which improved photovoltaic performance. The 1 : 2 blending ratio was optimal due to adequate charge transport pathways giving rise to moderate short circuit current density and fill factor. Adding 1,8-diiodooctane (DIO) additive into the 1 : 2 blend films further improved both the short circuit current density and fill factor, leading to an increased efficiency to 4.5% with PC60BM and 5.65% with PC70BM. These single junction solar cells exhibited a high open circuit voltage at ∼ 0.9 V. Photo-charge extraction by linearly increasing voltage (Photo-CELIV) measurements showed the highest charge carrier mobility in the 1 : 2 film among the three ratios, which was further enhanced by introducing the DIO. The Photo-CELIV measurements with varying delay times showed significantly higher extracted charge carrier density for cells processed with DIO. Tandem devices using P3HT:IC60BA as bottom cell and PBT-T1:PC60BM as top cell exhibited a high open circuit voltage of 1.62 V with 5.2% power conversion efficiency.

Development of a noninvasive continuous blood pressure measurement and monitoring system

Non invasive continuous blood pressure measurement system is more useful than conventional blood pressure measurement systems. The arterial system is extraordinarily well regulated blood delivery network in human body. It responds very quickly according to the body movements like altered body position, or in sudden excitation. So now a days continuous blood pressure monitoring devices are becoming more essential. Many types of blood pressure measurement devices are available. Those devices allow only few blood pressure readings in every 10 minutes. In contrast to them, we develop a very low cost noninvasive continuous blood pressure measurement and monitoring system. It measures blood pressure using volume oscillometric method and photoplethysmography technique during a long time period continuously. The rate of change of blood volume in an organ such as finger has a linear relationship with blood pressure. This rate of change of blood volume in finger is measured by an optical sensor network which estimates blood pressure. It displays the numerical value of systolic and diastolic blood pressure in a mini LCD. Our developed system is reliable, accurate and less expensive.

Improved performance by morphology control via fullerenes in PBDT-TBT-alkoBT based organic solar cells

In this work, we report improved performance by controlling morphology using different fullerene derivatives in poly{2-octyldodecyloxy-benzo[1,2-b;3,4-b]dithiophene-alt-5,6-bis(dodecyloxy)-4,7-di(thieno[3,2-b]thiophen-2-yl)-benzo[c][1,2,5]thiadiazole} (PBDT-TBT-alkoBT) based organic solar cells. PC60BM and PC70BM fullerenes were used to investigate the characteristic changes in morphology and device performance. Fullerenes affect device efficiency by changing the active layer morphology. PC70BM with broader absorption than PC60BM resulted in reduced device performance which was elucidated by the intermixed granular morphology separating each larger grain in the PC70BM/polymer composite layer which created a higher density of traps. However after adding additive 1,8-diiodooctane (DIO), a fibrous morphology was observed due to the reduced solubility of the polymer and increased solubility of PC70BM in chloroform. The fibrous morphology improved charge transport leading to an increase in overall device performance. Atomic force microscopy (AFM), photo-induced charge extraction by linearly increasing voltage (photo-CELIV), and Kelvin probe force microscopy (KPFM) were used to investigate the nanoscale morphology of the active layer with different fullerene derivatives. For the PC60BM based active layer, AFM images revealed a dense fibrous morphology and more distinct fibrous morphology was observed by adding DIO. The PC70BM based active layer only exhibited an intermixed granular morphology instead of a fibrous morphology observed in the PC60BM based active layer. However, addition of DIO into the PC70BM based active layer led to fibrous morphology. When additive DIO was not used, a wider distribution of surface potential was observed for PC70BM than the PC60BM based active layer by KPFM measurements, indicating that polymer and fullerene domains are separated. When DIO was used, a narrower distribution of surface potential for both PC70BM and PC60BM based active layers was observed. Photo-CELIV experiments showed larger extracted charge carrier density and mobility in the PC70BM/DIO film.

Morphological Evolution and Its Impacts on Performance of Polymer Solar Cells

In this paper, the role of fullerene loading on the nanomorphology and photovoltaic performance of alternating copolymer poly{2-octyldodecyloxy-benzo[1,2-b;3,4-b] dithiophene-alt-5,6-bis(dodecyloxy)-4,7bis(thiophen-2-yl)-benzo[c] [1,2,5]-thiadiazole} (PBDT-ABT-1) blend films was investigated. The morphology of blend films with different Phenyl C-60-butyric acid methyl ester (PCBM) mixing ratios and solvent additives was studied using atomic force microscopy (AFM) and energy-filtered transmission electron microscopy (EFTEM). AFM and EFTEM images showed difference in the intermixing of polymer with fullerene between 1:1, 1:2, and 1:3 weight ratios. Polymer/PCBM intermixed domain size increases with higher PCBM weight ratios. X-ray diffraction measurements on the pristine polymer and blend films cast without additives did not show any peaks, suggesting an amorphous nature of PBDT-ABT-1. EFTEM images from the donor/acceptor composite showed intermixed polymer-PCBM domains separated by the polymer boundary. Furthermore, EFTEM images for di-iodooctane (DIO) additive cast film revealed purer polymer domain. Photo-charge extraction by linearly increasing voltage measurement exhibited that charge extraction is highest in the nanomorphology sample with a weight ratio of 1:2, corresponding to the lowest bimolecular recombination and the highest charge carrier mobility.

Electronic energy meter with remote monitoring and billing system

Electronic energy meter is capable of taking readings and can store it into its memory. Taking energy meter reading is time consuming and an expensive task. The meter reader travels for a long distance and take the reading manually to prepare the bill. Consumers have to go to the billing office, stand in a long line and submit the bill. This is a boring job and time consuming also. It can be avoided by remote monitoring of electronic energy meter and prepaid billing system by the use of cash card. In this paper measurement of energy, remote monitoring, preparing of bill and billing system is presented. Low cost ATMEGA8L microcontroller is used here to control the whole system. Sampling of voltage and current is done by it. Then it processes data to achieve power in that instant. Then it stores the value of total energy consumed by the consumer and can calculate energy charge according to the tariff. LCD display is attached with this system to show total energy consumed, power factor and amount of charge etc. Communication between central energy distribution office and energy meter is done through power line. Complex tariff rate set up and cash card based billing is possible in this system. Electronic meter gives high accuracy for nonlinear loads than conventional rotating disc type electro-mechanical meter. Greater accuracy and stability can be maintained in this system.

Image compression using lifting based wavelet transform coupled with SPIHT algorithm

In the coming of era the digitized image is an important challenge to deal with the storage and transmission requirements of enormous data, including medical images. Compression is one of the indispensable techniques to solve this problem. In this paper, we propose an algorithm for medical image compression based on lifting base wavelet transform coupled with SPIHT (Set Partition in Hierarchical Trees) coding algorithm, of which we applied the lifting structure to improve the drawbacks of conventional wavelet transform. We compared the results with various wavelet based compression algorithm. Experimental results show that the proposed algorithm is superior to traditional methods for all tested images at low bit rate. Our algorithm provides better PSNR and MSSIM values for medical images only at low bit rate.

Optimization of Interconnecting Layers for Double- and Triple-Junction Polymer Solar Cells

In solution-processed tandem polymer solar cells, one of the most challenging parts is the optimization of interconnecting layers (ICLs) between subcells. In this study, ICLs were optimized for double- and triple-junction polymer solar cells. We investigated the robustness of PEDOT:PSS/AZO/PEIE ICL for tandem polymer solar cells. Solvent testing for ICL robustness showed a uniform coverage of the PEDOT:PSS layer when prepared without adding DMSO and IPA in PEDOT:PSS and with no use of additional filters. The performance of tandem polymer solar cells was investigated on different temperatures of interfacial layer. The PEDOT:PSS annealing temperature can be used from 120°C to 130°C, while aluminum-doped zinc oxide (AZO) temperature can be used from 120°C to 150°C. Lowering the annealing temperature in ICLs might help to fabricate triple-junction solar cells because they require more layers, and some low-bandgap polymers cannot sustain high temperature. However, reduction in annealing temperature in PEDOT:PSS, AZO, and PEIE led to lower FF and Jsc. A double-junction device Voc of 1.05 V and a triple-junction Voc of 1.4 V indicated that the ICLs worked effectively.

Microcontroller based health care monitoring system using sensor network

Non invasive and continuous measurement of blood pressure becomes popular now a day. This is very effective way for hypertensive patients to prevent cardiovascular problems and precisely regulate anti-hypertension cures. Blood pressure can be measured by conventional cuff-based sphygmomanometer or invasive instruments in non continuous mode. In this paper, we propose the microcontroller based continuous non invasive cuff less blood pressure measurement system with an alarm circuit for health care monitoring system. Light signal is used in sensor network section of this embedded system as light does not have any harmful effect on human body when it works in continuous mode. Pulse rate calculation and body temperature determination is also embedded in this system using sensor network. Accuracy of the system is found in acceptance range by comparing the results with the existing conventional systems. If BP reading, heart rate or body temperature exceeds the standard range for any patient, the system is able to notify using an alarming circuit. The whole system is controlled by microcontroller ATMEGA8L. The overall system is reliable, accurate, portable, trust worthy, user friendly and cost effective.

Vertical handover decision using fuzzy logic in a heterogeneous environment

Mobile users can move between the different wireless networks because several heterogeneous wireless networks are deployed and can be used in a small area. So there need vertical handover issues in an effective manner. This paper proposed two vertical handover scheme based on fuzzy interference system and subtracting clustering method in a heterogeneous environment and simulates to verify performance. This will be a method for easy and fast handover between different protocol users according to priority based.