Quantum Engineering of InAs/GaAs Quantum Dot Based Intermediate Band Solar Cells

Abstract

The efficiency of a solar cell can be substantially increased by opening new energy gaps within the semiconductor band gap. This creates additional optical absorption pathways which can be fully exploited under concentrated sunlight. Here we report a new approach to opening a sizable energy gap in a single junction GaAs solar cell using an array of InAs quantum dots that leads directly to high device open circuit voltage. High resolution imaging of individual quantum dots provides experimentally obtained dimensions to a quantum mechanical model which can be used to design an optimized quantum dot array. This is then implemented by precisely engineering the shape and size of the quantum dots resulting in a total area (active area) efficiency of 18.3% (19.7%) at 5 suns concentration. The work demonstrates that only the inclusion of an appropriately designed quantum dot array in a solar cell has the potential to result in ultrahigh efficiency under concentration.

Design and fabrication of InAs/GaAs QD based intermediate band solar cells by quantum engineering

“…The efficiency of the device shown in Fig7(b) is η = 18.4% which increases to a record efficiency under concentration of 19.7% when the area of the contacts is taken into account (the active area efficiency). [15] To the best of our knowledge this is the highest reported efficiency for a InAs QD-IBSC.…”

Enhanced quantum yields and efficiency in a quantum dot photocell modeled by a multi-level system

“…We proposed the QD photocell modeled by a multi-level model generated from the theoretical prototype mentioned in [14], and an intermediate band was introduced in this multi-level QD photocell. The intermediate band may be grown by super-lattices or organized QDs [25,26], and μ c , μ v represent chemical potentials of a cathode in the conduction band and an anode in the valence band (seen figure 1(a)). Therefore, the single bandgap between the conduction and valence band was divided into two sub-bands, i.e.…”

“…With the multi-photon absorption contributing to the quantum yields in heart, we propose an enhanced quantum yields scheme in a quantum dot (QD) photocell modeled by a multi-level system, which can fully absorb the low-energy photons. And the introduced intermediate band in this proposed photocell model may be achieved by super-lattices and organized QDs [25,26]. Thus, the separated state may be created due to quantum size effects [27], and two solar photons below the energy gap can be absorbed by two sub-bands simultaneously.…”

Gas Sensitivity of In0.3Ga0.7As Surface QDs Coupled to Multilayer Buried QDs

“…III-V semiconductor quantum dots (InAs, InGaAs, InP, etc.) formed in self-organized growth mode are typical nanomaterials, widely used in optoelectronic fields like laser, photodetector, LED, and solar cell [5][6][7][8][9]. Lately, InGaAs (InP) surface quantum dots (SQDs) have also attracted much attention in the application field of gas sensing materials [10][11][12].…”