Influence of Geometrical Shape on the Characteristics of the Multiple InN/InxGa1-xN Quantum Dot Solar Cells.

Asmae El Aouami,Laura M Pérez,Kawtar Feddi,Maykel Courel,Francis Dujardin,Manuel J Suazo,David Laroze,Mohamed El-Yadri,El Mustapha Feddi

doi:10.3390/nano11051317

Abstract

Solar cells that are based on the implementation of quantum dots in the intrinsic region, so-called intermediate band solar cells (IBSCs), are among the most widely used concepts nowadays for achieving high solar conversion efficiency. The principal characteristics of such solar cells relate to their ability to absorb low energy photons to excite electrons through the intermediate band, allowing for conversion efficiency exceeding the limit of Shockley–Queisser. IBSCs are generating considerable interest in terms of performance and environmental friendliness. However, there is still a need for optimizing many parameters that are related to the solar cells, such as the size of quantum dots, their shape, the inter-dot distance, and choosing the right material. To date, most studies have only focused on studying IBSC composed of cubic shape of quantum dots. The main objective of this study is to extend the current knowledge of IBSC. Thus, we analyze the effect of the shape of the quantum dot on the electronic and photonic characteristics of indium nitride and indium gallium nitride multiple quantum dot solar cells structure considering cubic, spherical, and cylindrical quantum dot shapes. The ground state of electrons and holes energy levels in quantum dot are theoretically determined by considering the Schrödinger equation within the effective mass approximation. Thus, the inter and intra band transitions are determined for different dot sizes and different inter dot spacing. Consequently, current–voltage (J-V) characteristic and efficiencies of these devices are evaluated and compared for different shapes. Our calculations show that, under fully concentrated light, for the same volume of different quantum dots (QD) shapes and a well determined In-concentration, the maximum of the photovoltaic conversion efficiencies reaches 63.04%, 62.88%, and 62.43% for cubic, cylindrical, and spherical quantum dot shapes, respectively.

Highlights

We study the behavior of different parameters and characteristics of a multiple quantum dots solar cell (MQDSC) structure, when considering cubic, spherical, and cylindrical shapes, the inter dot space and alloy composition
It is worth noting that in all calculations, we have chosen an inter dot distance H = 8 nm, which guarantees the non-overlapping between wave functions of QDs; only discrete levels within the bandgap are created
Even if all of the QD shape has the same volume, the confinement behavior is different, leading to the conclusion that the shape of QD affects the electronic properties of nanomaterials, something that could help in the manufacturing of optoelectronic devices with a range of features

Summary

Introduction

The photovoltaic device is the system that transforms solar irradiation directly into electricity, which can be after that stored into batteries for useful purposes. Numerous generations of photovoltaic devices, which are differenced by their efficiency, are commercially accessible in the market. The first-generation of the solar cells was made-up of crystalline silicon, which was inexpensive, more efficient at low temperatures, require less area, and it has been able to attain an efficiency of up to 26% [1,2,3]. The main problem of the 1st generation of solar cells is the un-direct band-gap transitions

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