Pramila Mahala

Optimization of p-GaN/InGaN/n-GaN Double Heterojunction p-i-n Solar Cell for High Efficiency: Simulation Approach

We have conducted numerical simulation of p-GaN/In0.12Ga0.88N/n-GaN, p-i-n double heterojunction solar cell. The doping density, individual layer thickness, and contact pattern of the device are investigated under solar irradiance of AM1.5 for optimized performance of solar cell. The optimized solar cell characteristic parameters for cell area of 1  × 1 mm2 are open circuit voltage of 2.26 V, short circuit current density of 3.31 mA/cm2, fill factor of 84.6%, and efficiency of 6.43% with interdigitated grid pattern.

A study on the 2D simulation of Pt/InGaN/GaN/metal Schottky junction solar cell

We report on the 2D simulation of the heterojunction-based M/InxGa1-xN/GaN/M Schottky junction solar cell and studied the variations of different factors such as indium mole fraction, thickness, temperature and doping density of the n-InxGa1-xN active layer on the solar cell performance. The current–voltage characteristics have been simulated at various temperatures, in the range from 100 to 700 K. The results show that the value of all the characteristic parameters such as open-circuit voltage, fill factor and conversion efficiency, except short-circuit current density, decreases with increasing temperature. The barrier height and ideality factor of the Pt/In0.21Ga0.79N/GaN/M Schottky junction solar cell have been evaluated from current–voltage characteristics and at 300 K they are 0.53 eV and 0.39, respectively. The photovoltaic output under AM0 sunlight illumination of the optimized Schottky junction solar cell at room temperature is 0.58 V (open-circuit voltage), 5.36 mA cm−2 (short-circuit current density), 67% (fill factor) and 1.55% (conversion efficiency). The behavior of these parameters with the underlying physics is presented.

Graphene as transparent and current spreading electrode in silicon solar cell

Fabricated bi-layer graphene (BLG) has been studied as transparent and current spreading electrode (TCSE) for silicon solar cell, using TCAD-Silvaco 2D simulation. We have carried out comparative study using both Ag grids and BLG as current spreading electrode (CSE) and TCSE, respectively. Our study reveals that BLG based solar cell shows better efficiency of 24.85% than Ag-based cell (21.44%), in all of the critical aspects, including generation rate, recombination rate, electric field, potential and quantum efficiency. Further BLG based cell exhibits pronounce rectifying behavior, low saturation current, and good turn-on voltage while studying in dark.

The Effect of Indium Composition on Open-Circuit Voltage of InGaN Thin-Film Solar Cell: An Analytical and Computer Simulation Study

In this work we have evaluated the open-circuit voltage developed across a metal/n-InGaN Schottky junction solar cells through both analytical and computer simulation as a function of varying indium composition. Our study includes four different systems such as Au/n-InGaN/Al, Pd/n-InGaN/Al, Ni/n-InGaN/Al and Pt/n-InGaN/Al with a variation of Indium composition. It is reported that there exists a certain value of Indium composition which decides the InGaN as a Schottky junction solar cell. This cut-off value of Indium is calculated for all the systems by analytical and simulated approach and a comparison is also made between them. The difference of 19.4% for Au, 18.91% for Pd, 20.50% for Ni and 15.15% for Pt between analytical and simulation is reported.

Photovoltaic and impedance spectroscopic characteristics of heterojunction of graphene-PEDOT:PSS composite and n-silicon prepared via solution-based process

Recent investigations involving nanoscale energy conversion using two-dimensional nanomaterials such as graphene and transition metal dichalcogenides (TMDs) hold promise to mitigate future energy challenges. The heterojunction devices designed by interfacing 2D layers with 3D bulk semiconductors (2D/3D heterojunctions) including graphene/silicon and TMDs/silicon are widely explored for the photovoltaic characteristics. Developing a thorough understanding of the interfacial chemistry via impedance spectroscopic analysis will leverage the potential of these 2D/3D junctions for large-scale integrations. Here, the non-vacuum solution-processed reduced graphene oxide (rGO), poly(3,4-ethylenedioxythiophene):polystyrene sulphonate (PEDOT:PSS) and their composite (PEDOT:PSS(rGO)) were spin coated on the silicon (n-Si) substrates for fabrication of heterojunctions, with the device construct of rGO/n-Si, PEDOT:PSS/n-Si and PEDOT:PSS(rGO)/n-Si having Ohmic metal contacts in both top and bottom. The significant efficiency improvement of three orders for PEDOT:PSS(rGO)/n-Si device over the rGO/n-Si and PEDOT:PSS/n-Si heterojunction devices can be attributed to (i) increased conducting channels in the active region and (ii) reduced series resistance. Further, the impedance spectroscopy is employed to understand the interfacial chemistry of PEDOT:PSS(rGO)/n-Si solid-state junction, which is explained by a parallel resistance–capacitance circuit model.

Grid contact optimization of p-i-n GaN/InGaN solar cell

In this study, we have conducted numerical simulations to design the device contact pattern for the optimized performance of InGaN p-i-n solar cells. GaN/InGaN p-i-n solar cell studied with two different contact patterns, with grid pattern and without grid pattern. Solar characteristic parameters for both geometries are simulated with 1 × 1 mm2 device areas while varying grid spacing and number of grids. An improved efficiency from 4.16 % to 6.34 % is observed with grid pattern and with optimized grid spacing of 225 microns.