Mohammad Houshmand

CONSTRUCTION COMPONENTS ENGINEERING IN INTERMEDIATE BAND SOLAR CELLS

The parameter electron filling factor can be taken as a scale for the electronic states in the intermediate band which should be de-localized and thus the unconfined electrons at the quantum dots. For three different value of electron filling factor, the sunlight concentration effect on the efficiency of a quantum dot solar cell is calculated. The maximum point of efficiency and optimum thickness of the cell obtained under three different sunlight concentrations. We show the importance of electron filling factor as a parameter to be more considered. This parameter can be controlled by the quantum dots size and distance between quantum dot layers in the active region. Analysis of above mentioned parameters suggest that to attain a maximum efficiency, the size of the quantum dots and the distance between the periodically arrayed dot layers have to be optimized. In addition, sunlight concentration is recommended as an effective approach to have high efficiency and low cost level solar cells.

AN EQUIVALENT CIRCUIT MODEL PROPOSED FOR THE INTERMEDIATE BAND NANOSTRUCTURED QUANTUM DOT SOLAR CELLS

The equivalent circuit of the p-i-n structure has been considered and developed for the quantum dot intermediate band solar cells where the nanoparticles are inserted in the active region of the diode. The admittance of the circuits are calculated consisting of frequency dependent capacitance and conductance. The presence of quantum dot layers in the active region of the diode increases the capacitance and conductance of the cell in lower frequencies. However, the number of QD cannot be increased and has an optimum.

Modeling of optical losses in graphene contacted CIGS solar cells

For the first time, an optical model is applied to superstrate configuration of CdS/CIGS thin film solar cells with graphene front/back contact (FC/BC) to simulate the loss in current density and efficiency. Graphene shows to be a great candidate to replace with the metallic BC transparent conductive oxides as the front electrode. Our model is based on the refractive index and extinction coefficient and takes into account the reflection and absorption in interfaces and layer’s thickness, respectively. CIGS cells with graphene as front electrode have a lower current density and efficiency than the one with graphene BC. However, the bifacial configuration shows a higher current density and efficiency, mostly because of a higher transmission rate. The interference effect was observed in simulation of transmission rate of hybrid cells representing that graphene can cause multiple reflection. We simulated the device parameters versus the ZnO layer’s thickness, which is essential for high quality interfaces. However, the simulation results are also consistent when CdS thickness is replaced with inorganic ZnO.

Hybrid Structure for Solar Cells Based on SWCNT/CdS

Recently, we considered the application of carbon nanotubes as the buffer layer between the CdS and Cu (In,Ga)Se2 thin film solar cells. In this work the structure of a p-n heterojunction solar cell is analyzed including the single walled carbon nanotubes as the absorber and CdS as n-type semiconductor window layer. The interface and current-voltage characteristics of this proposed structure are studied exerting the general formulation of the p-n heterojunction solar cells proposed by Fonash. We propose that SWCNTs/CdS heterojunction solar cell can overlap with a main part of the sunlight spectrum leading to improve efficiency and short circuit current. The interesting property of such devices is that the light can inter to the device from the absorber as carbon nanotubes are transparent semiconductor nanostructures. The results of this study can be extended to graphene nanolayers as it has been extensively studied by the PV community in recent years.

Numerical Analysis of TiO2/Cu2ZnSnS4 Nanostructured PV Using SCAPS-1D

A nanostructured solar cells consist of a nonporous n-type TiO2 nanoparticles and a p-type semiconductor Cu2ZnSnS4 (CZTS) thin film has been numerically simulated using SCAPS-1D tool. The performed theoretically analysis is compared with the experimental reported data. The band diagram, IV characteristics and quantum efficiency of this structure is considered. The benefit of both TiO2 and CZTS material leads to more than 10% conversion efficiency which is promising between the nanoparticle-based heterojunbctions proposed for PV applications.

Simulation of carbon nanotubes/GaAs hybrid photovoltaic using AMPS-1D

The performance and characteristics of a hybrid heterojunction single-walled carbon nanotube/GaAs solar cell were modelled and numerically simulated using the AMPS-1D device simulation tool. The device physics and performance parameters with different junction parameters were analysed. The results suggest that the open-circuit voltage changes very slightly by changing the work function, acceptor and donor density, while the other electrical parameters reach an optimum value. Increasing the concentration of a discrete defect density in the absorber layer decreases the electrical parameters. The current–voltage characteristics, quantum efficiency, band gap and thickness variation of the photovoltaic response will be quantitatively considered.