Performance Analysis of Quantum Dot Intermediate Band Solar Cell (QD IBSC) (original) (raw)
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Two intermediate bands solar cells of InGaN/InN quantum dot supracrystals
Applied Physics A, 2014
Two intermediate bands solar cells (2-IBSC) of In x Ga 1-x N/InN cubic quantum dot supracrystals were designed in this work. Position and width of the two IBs were determined, the performance parameters including short circuit current density, open circuit voltage and photoelectric conversion efficiency were numerically calculated, and their variations with adjustable variables such as In content, average size of QDs and interdot spacing were further discussed. Within a certain range, the influence from these adjustable variables on the first IB stronger than that on the second one was indicated. The cause of the maximum efficiency in the present cell lower than the one of another 2-IBSC with different material [Jenks and Gilmore, J Renew Sustain Energy 2:013111 (2010)] was probed, while the reason for the maximum efficiency of the studying device near to that of 1-IBSC with same material [Zhang and Wei, Appl Phys A 113:75 (2013)] was clarified.
The feasibility of high-efficiency InAs/GaAs quantum dot intermediate band solar cells
Solar Energy Materials and Solar Cells, 2014
In recent years, all the operating principles of intermediate band behaviour have been demonstrated in InAs/GaAs quantum dot (QD) solar cells. Having passed this hurdle, a new stage of research is underway, whose goal is to deliver QD solar cells with efficiencies above those of state-of-the-art single-gap devices. In this work, we demonstrate that this is possible, using the present InAs/GaAs QD system, if the QDs are made to be radiatively dominated, and if absorption enhancements are achieved by a combination of increasing the number of QDs and light trapping. A quantitative prediction is also made of the absorption enhancements required, suggesting that a 30 fold increase in the number of QDs and a light trapping enhancement of 10 are sufficient. Finally, insight is given into the relative merits of absorption enhancement via increasing QD numbers and via light trapping.
Characterisation of InAs/GaAs quantum dots intermediate band photovoltaic devices
IET Optoelectronics, 2014
The authors report on the structural, the optical and the electrical properties of solar cells containing 20 layers of doped InAs/GaAs quantum dots (QDs). The structures were grown by molecular beam epitaxy and contain n dopant sheet densities of 8 and 16 × 10 10 cm −2 , respectively, in between the QD layers. Under a 1 sun illumination, the open-circuit voltage (V oc) and the efficiency of the 8 × 10 10 cm −2 n-doped sample were increased to values of 0.73 V and 9.7%, respectively, compared with a reference undoped sample (a V oc of 0.70 V and an efficiency of 9.0%). However, the short-circuit current density (J sc) decreased from 20.1 to 17.4 mA/cm 2 indicating bandfilling within the QD array.
Quantum dot intermediate band solar cell
2000
This paper discusses the possibility of manufacturing the intermediate band solar cell (IBSC), a cell with the potential of achieving 63.2% of efficiency under concentrated sunlight, using quantum dot technology. The 0-dimensionality nature of the dots avoids electron thermalisation between bands enhancing the possibilities for radiative recombination between bands and making possible the existence of three quasi-fermi levels, some of the pivots the theory of the IBSC is sustained on. In this sense, it is suggested that an InGaAs/AlGaAs system could be used for band engineering the optimum bandgaps of the IBSC cell (0.71 and 1.24 eV). Dots should be about 40 Å of radius, spaced in the range of 100 Å and distributed in a three dimensional array. The Stranski and Krastanow method is proposed as a technology for achieving this goal. The possibility of n-doping the dots is also discussed
Progress in quantum-dot intermediate band solar cell research
The intermediate band solar cell concept can be implemented in practice by means of quantum dots (QDs), but a number of challenges must be solved in order to make progress. This paper describes some of them: a) the problem of having the quantum dots embedded in the space charge region, b) the identification of the energy levels involved in the QD system and c) the weak absorption provided by the dots. Regarding the first, the inclusion of semiconductor dumping field layers sandwiching the region containing the stack of QDs is suggested as a way to drive the QDs into a flat band potential region. Concerning "b", the intermediate band is found to be separated from the conduction band by only 0.2 eV, far from the optimum value. Finally, the weak light absorption provided by the dots is discussed as a factor, together with the low intermediate band to conduction band bandgap that prevents a significant quasi-Fermi level split between the IB and the CB under normal illumination conditions.
Recombination through quantum dots (QDs) is a major factor that limits efficiency of QD intermediate-band (IB) solar cells. Our proposal for a new IB solar cell based on type-II GaSb QDs located "outside" the depletion region of a GaAs p-n-junction aims to solve this problem. The important advantage of proposed heterostructure appears due to the "outside" location of IB. Such IB does not assist generation of additional leakage current flow through the depletion region. Carriers cannot escape from "outside" QDs through the buffer layer and the depletion region into GaAs substrate by tunneling because QDs are far from the depletion layer. Only solar photon or thermal assistance may enable electron escape from QDs. Such type-II QD IB solar cell concept promises an efficiency enhancement relative to that of GaAs solar cells.
Elements of the design and analysis of quantum-dot intermediate band solar cells
Thin Solid Films, 2008
We have demonstrated recently that two below bandgap energy photons can lead to the creation of one electron-hole pair in a quantum-dot intermediate band solar cell (QD-IBSC). To be effective, the devices used in the experiments were designed to a) half-fill the intermediate band with electrons; b) to allocate the quantum dots in a flat-band potential region, and c) to prevent tunnelling from the n emitter into the intermediate band. QD-IBSCs have also shown degradation in their open-circuit voltage when compared with their counterparts without quantum dots. This loss is due to the presence of the intermediate band (IB) together with the incapacity of the quantum dots to absorb sufficient below bandgap light as to contribute significantly to the photogenerated current. It is predicted, nevertheless, that this voltage loss will diminish if concentration light is used leading to devices with efficiency higher than single gap solar cells. A circuit model that includes additional recombination levels to the ones introduced by the IB is described to support this discussion.
Superlattices and Microstructures, 2019
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Investigation of InAs/GaAs 1−x Sb x quantum dots for applications in intermediate band solar cells
Solar Energy Materials and Solar Cells, 2016
Self-assembled InAs quantum dots (QD) in a GaAs 1 À x Sb x matrix are studied using photoluminescence. Increasing the Sb composition in the GaAs 1 À x Sb x matrix reduces the effective band gap while lowering the valence band offset, resulting in transition from a type-I to type-II band alignment for Sb compositions above 14%. The optimized quantum dots are incorporated in an InAs/GaAs 1 À x Sb x based p-in solar cell with a degenerate valence band and therefore optimum intermediate band structure. Temperature dependent external quantum efficiency measurements show an enhancement in the QDs region with increasing temperature.