Kamlesh Patel

Multilayer graphene as a transparent conducting electrode in silicon heterojunction solar cells

In this paper, the structure of a graphene/silicon heterojunction solar cell has been studied under simulated conditions. The parameters of the cell’s layers have been optimized by using AFORS-HET software. Instead of reported 2D nature, we considered graphene as 3D in nature. To ensure the formation of Schottky junction, electrical contacts were made along c-axis to collect the minority carriers, which generate upon illumination. By optimizing the various parameters of n-type multilayer graphene, we achieved the best-simulated cell with the power conversion efficiency of 7.62 % at room temperature. Up to 40 layers of n-type graphene, the efficiency found to be constant and enhanced only to 7.623 %. After further optimization of the parameters of p-crystalline silicon wafer, a maximum efficiency of 11.23 % has been achieved. Temperature dependence on the cell performance has also been studied and an efficiency of 11.38 % has been achieved at 270 K. Finally, we have demonstrated that n-type multilayer graphene can act as an excellent transparent conducting electrode.

Potential application of mono/bi-layer molybdenum disulfide (MoS2) sheet as an efficient transparent conducting electrode in silicon heterojunction solar cells

In this paper, we have simulated the structure of n-type MoS2/silicon heterojunction solar cell and studied its function under different conditions. The optimization of parameters of the cells layer has been carried out by using AFORS-HET software. In the present study, MoS2 has been considered as 3-D in nature instead of the reported 2-D nature. In order to ensure the formation of Schottky junction, electric contact has been made along the c-axis to collect the minority charge carriers. After optimizing the various parameters of n-type single layer MoS2, power efficiency of 12.44% has been achieved at the room temperature, which has further decreased to 9.042% as the layer number has increased up to 40. Furthermore, after optimizing the parameters of silicon wafer maximum efficiency of 16.4% has been achieved. Temperature dependence of the cell performance has also been studied and the maximum efficiency has been achieved at 300 K. In the present study, we have demonstrated that n-type ultrathin layer o...

Investigating the effects of graphene-based superstrate on characteristic of microwave filters

Abstract This paper presents a study based on changes in the cut-off frequency and sharpness of different types of filter by loading with glass and graphene–glass superstrate. Design and fabrication of four basic types of microwave filter – low-pass, high-pass, band pass, and band stop filter are presented and S-parameters are measured with superstrate. The impact of superstrate on the filter characteristics such as cut-off frequency, bandwidth, and sharpness are analyzed experimentally by comparing these characteristics for without superstrate and with superstrate. The superstrate loading resulted in the decrease of cut-off frequency for low-pass and high-pass filter, whereas the bandwidth is decreased for band pass filter and band stop filter with larger shift in high cut-off frequency. Such effects have been confirmed by the simulation of low-pass filter and band pass filter on placing a glass. It is estimated from the filter responses that graphene–glass has conducting as well as dielectric nature compared to glass in the frequency range of study. It has been shown that the cut-off frequency and bandwidth can be tuned by dielectric kind of superstrate without varying the physical dimension of filter.

Application of RLGC modeling in probing the electrical properties of monolayer graphene at microwave frequencies

Abstract The S-parameters of the microstrip line loaded with graphene on glass and graphene on quartz as a superstrate are measured from 10 MHz to 26.5 GHz. These parameters have shown only a little difference compared to glass or quartz loaded microstrip line. Then, de-embedded S-parameters of superstrate loaded microstrip line are modeled as the transmission line (RLGC) parameters and these parameters are obtained with frequency. Their comparison with unloaded microstrip line shows large changes in R and G whereas, in L and C parameters, no significant changes have been noticed with superstrates. In these parameters, larger percentage changes for graphene on glass have showed a poor contact between two than graphene and quartz. Changes in R and G parameters confirmed that graphene has modified the surface resistance and effective relative permittivity on loading the microstrip line.

Hexagonal surface coil for 1.5T MRI scanner

Radio-frequency coil is the core component used in the detection of nuclear magnetic resonance signal. Usually the radio frequency coil is designed for operation on a specific magnetic field strength based magnetic resonance imaging system. This paper describe the method of implementing a hexagonal surface type receive only radio frequency coil which has ability to detect the nuclear magnetic resonance signal of 1H nuclei at 63.87 MHz resonance frequency for 1.5T magnetic resonance imaging scanner. The RF coil in MRI is used for excitation of the magnetization and to receive the signal from the excited spins. A surface coil is usually a loop of conducting material designed specifically for localized body regions. These coils have high SNR and uniform sensitivity. The Return loss of fabricated surface coil is 24.521 dB and bandwidth is 0.188 MHz.

Effective relative permittivity and characteristic impedance of graphene loaded microstrip line by scalar S-parameters

Graphene film has particular applications at the microwave frequencies because as the number of layers increases, the permittivity and conductivity are modulated. Particularly, an effective relative permittivity of graphene is of high interest. In the present work, effective relative permittivity and characteristic impedance for three kind of structures where microstrip line is either in air or loaded by glass or by graphene film on the glass substrate have been determined. The scalar S-parameters have been measured by adopting both transmission-reflection and short-open methods. The propagation constant and effective relative permittivity have been calculated and found to be nearly same for the both methods with maximum difference of 0.27% and 1.87%, respectively. However, the characteristic impedance values have significant variations as high as 12.13%. Enhanced effective relative permittivity in the range of 3.7 to 4.12 has been observed in the frequency range 1 to 8 GHz, if graphene film on the glass ...