Quantum dots solar cells

Full scale Optimisation process
Figure 1. Full scale Optimisation process

Photovoltaic (PV) devices based on semiconductor materials have been demonstrated to be a good option for electricity generation. Many research efforts have been devoted to semiconductors solar PV in order to improve their efficiencies.

One of the ways is to extend the absorption range of the device to the mid infrared. This can be achieved with the insertion of quantum dots (QDs) into a host lattice, which introduce new energy states. The doping of such structures has also proved to enhance the open-circuit voltage which in turn increases the device efficiency.

Thus, the key challenge though is the growth of QDs based materials with expanded absorption spectrum and high open circuit voltage (Voc). 

J-V curves for different QD layer periodicity materials measured at 1sun light intensity (100 mW/cm2) at room temperature
Figure 2. J-V curves for different QD layer periodicity materials measured at 1sun light intensity (100 mW/cm2) at room temperature

This project is concerned with the development of advanced solar cell architectures and a systematic investigation of the properties of InAs/GaAs QD systems with the objective to achieve an enhancement of solar cell performance. Epitaxial growth using state-of–the-art MBE, optical absorption, photoluminescence and high resolution x-ray diffraction (DCXR) measurements are part of the project activities as well as device fabrication and characterization of novel solar cell structures.

Optimization is performed following the process depicted in Figure 1. Recently, as a part of the efficiency optimization process it has been proved that reducing the number of undoped QD stacked layers, up to the number of 10, the efficiency of the device is improved (See figure 2) improving the solar cell efficiency up to ~10% being this an excellent value for such simple device.

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