Md. Iqbal Bahar Chowdhury

A simulink based generalized model of PV cell / array

This work proposes a Simulink-based Model of a photovoltaic (PV) system using the two-diode model of a PV solar cell. The series and shunt resistance of the solar cell are estimated in this model by an efficient iteration method. The number of required input parameters are four and are based on the available information from the PV module datasheet. The developed model allows the user to predict a PV cells current-voltage and power-voltage characteristics curves by varying sunlight, cell temperature, ideality factor and series resistance value. The model is also applicable under partial shading/module mismatch condition. The characteristics curves obtained by the simulation of the proposed model is matched with the data provided by the manufactures.

An analytical model of dark saturation current of silicon solar cell considering both SRH and Auger recombination

The analytical modeling of dark saturation current of a solar cell conventionally incorporates either SRH (Schokley-Reed-Hall) recombination or Auger recombination, since simultaneous consideration of both these mechanisms results in mathematical complexity. On the other hand, non-uniform doping profile is used in the practical solar cells for which a retarding electric field is introduced and as a result, the dark saturation current is reduced. Moreover, the doping level increases day by day to meet the requirements for the improvement of solar cell performances. However, the heavy doping level as well as the non-uniformity of the doping profile lead to the position and field dependency of the carrier mobility and also, to the doping dependency of the carrier lifetime. Moreover, the bandgap narrowing effects also become significant at such heavy doping levels. This later effect causes the retarding electric field for the dark saturation current to reduce and hence, increases the dark saturation current. Therefore, all these effects should be incorporated in the analytical modeling of the dark saturation current of modern solar cells. However, consideration of all these effects especially simultaneous consideration of both SRH and Auger recombination mechanisms leads the governing equation to a second order, nonlinear, variable-coefficient differential equation and hence, causes the differential equation to be analytically intractable. In this paper, the analytical intractability problem has been resolved by using an exponential approximation technique, which can approximate any exponential-like profile (Gaussian, complementary error function etc.) or any doping dependent transport parameter (mobility, lifetime etc.) into a simple exponential function. Therefore, this technique can be used for any doping level and for arbitrary doping profile. The developed model shows that the changes in the dark saturation current due to the simultaneous consideration of SRH and Auger recombination becomes significant compared to the consideration of any one recombination mechanism. The model results also show that the change in the dark saturation current considering both recombination mechanisms increases with the doping level.

Analytical modeling of J-V characteristics of CIGS based thin film solar cell considering voltage and space dependent electric field in the absorber layer

This paper focuses on developing an analytical model to analyze the current-voltage (J-V) characteristics of lightly doped CIGS-based thin film solar cell considering the series resistance and the voltage-space dependent electric field in the absorber layer. The mathematical intractability evolved for these considerations has been resolved by employing the concept of perturbation theory. Effects of various parameters such as intensity of light, electron lifetime and hole lifetime have been investigated using the developed model. Simulation results show that the proposed model is helpful in providing better physical insight.

Current-voltage characteristics of CdS/CdTe thin film solar cells: An analytical approach

Based on the perturbation theory, an analytical model has been developed for J-V characteristics of lightly-doped CdTe-based thin film solar cells. The developed model is computationally more efficient and provides better physical insight.

Effect of field dependent mobility and simultaneous consideration of both SRH and auger recombination on the analytical modeling of internal quantum efficiency of a si-solar cell

In this paper an analytical model of internal quantum efficiency of a silicon solar cell has been developed to show the effects of field dependency of the carrier mobility and the simultaneous consideration of SRH and Auger recombination mechanisms in a non-uniformly doped emitter. In developing this model the doping dependency of carrier lifetime as well as the band-gap narrowing effect due to heavy emitter doping level is considered. An exponential approximation technique is used to deduce an analytically solvable governing differential equation. The developed model shows that the internal quantum efficiency significantly varied due to the field-dependency of carrier mobility and also, due to the simultaneous consideration of SRH and Auger recombination.

Analytical modeling of base transit time considering recombination in the non-uniformly doped base

The main objective of this paper is to show that recombination in the base needs to be taken into account in determining base transit time τB. In previous analytical works for τB, recombination in the base was neglected. In this paper both drift and diffusion currents for electron and hole are considered in obtaining minority carrier profile n(x). In the model, both SRH and Auger recombination are considered. The energy-bandgap-narrowing effects due to heavy doping, velocity saturation as well as doping and field dependent mobility are considered. The model shows that recombination has significant effects on the base transit time of a heavily doped base.

Base transit time of a bipolar junction transistor considering majority-carrier current

In this paper an analytical expression for base transit time tau_B for an npn bipolar transistor considering majority-carrier current density is obtained. For finding tau_B, expressions for minority-carrier electron current density J_n, majority-carrier hole current density J_p and electron concentration, n(x) are analytically derived. In the model energy-bandgap-narrowing effects due to heavy doping, velocity saturation as well as doping and field dependent mobility are considered. It is found that, in the low-injection condition, tau_B depends on J_p and its value is found greater than the value if Jp is neglected. In finding tau_B, previous works neglected J_p. The closed-form analytical expressions offer a clear physical insight into device operations at various bias conditions.

Exploring the opportunity of using graphene as the transparent conducting layer in CZTS-based thin film solar cells

This work explores the opportunity of the use of graphene as the transparent conducting (TC) layer instead of conventional transparent conducting oxide (TCO) such as indium tin oxide (ITO) in the CZTS based solar cells which is recently evolved as one of the most promising thin film solar cells. It has been known that graphene has higher transmittance and conductance and is cheaper than the widely used ITO. Based on the MATLAB simulations, this work proves that graphene can be used as the better alternative than ITO as the transparent conducting layer. Moreover, simulations show that the use of graphene can reduce the amount of CZTS material and hence, reduce the cost of solar cell as optimum absorber width based on maximum possible conversion efficiency is found less for the graphene-TCL based solar cells.

Analytical modelling of Cds/CdTe based thin film solar cells considering surface recombination

This work develops an analytical model including the effect of series resistance as well as the surface recombination occurred at the edges. Mathematical intractability caused for the inclusion of series resistance has been resolved using the concept of the perturbation theory. Introducing a new boundary condition at the emitter edge of the fully depleted absorber region, the effects of surface recombination can be included in the analysis. The proposed model not only shows the importance of inclusion of surface recombination in the analysis but also explains the effects of variation of series resistance and absorber width and the effects of stress as well. Therefore, the proposed model demonstrates the underlying physics of CdS/CdTe solar cell better.

Modeling of J-V characteristics of CZTS based thin film solar cells including voltage and space dependent electric field in the absorber layer

This work proposes an analytical model incorporating the effects of the series resistance to deduce the current-voltage characteristics for ZnO/CZTS based thin film solar cell. The evolving mathematical intractability for the inclusion of the series resistance has been resolved by using the concept of perturbation theory. The various effects utilizing the proposed model has been observed and analyzed. The model may be helpful to gain more physical insight of the CZTS based solar cells.