In‐plane coupling effect on absorption coefficients of InAs/GaAs quantum dots arrays for intermediate band solar cell

Abstract

Coupled semiconductor quantum dot (QD) arrays emerged recently as promising structures for the next generation of high efficiency intermediate band solar cell (IBSC), because of their ability to facilitate the formation of minibands. The quantum coupling effect that exists between states in QDs in an array influences the electronic and optical properties of such structures. So far, great experimental and theoretical efforts have been devoted to study the vertically coupled QD arrays. We present here a method based on multi-band k p Hamiltonian combined with periodic boundary conditions, applied to predict the electronic and optical properties of InAs/GaAs QDs-based lateral QD arrays. Formation of the intermediate band (IB) in all cases was achieved via delocalisation of the electron ground state (e0). We show that the IB in a laterally coupled QD-IBSC is more robust against external electric field from the solar cell's pn junction than that in a vertically coupled arrangement. Because of symmetry of the QD array lattice and QD states itself, which are C 2v for the zinc blend QDs, the electronic and absorption structures were obtained via sampling throughout the reciprocal space in the first Brillouin zone of QD arrays.the IB, and the second photon subsequently pumps another electron from the IB to the conduction band (CB). To this end, it is necessary that the IB is half filled with electrons so that it can supply electrons to the CB as well as receive them from the VB. The electron-hole pairs generated in this way add up to the conventionally generated ones by the absorption of a single photon, the third one, pumping an electron from the VB directly to the CB. Therefore, if the quasi-Fermi level separations between bands are sustainable upon external excitation, the photocurrent of the SC, and ultimately its efficiency, is enhanced. According to this concept, increase in photocurrent in IBSC occurs without degradation of the output voltage of the cell. The output voltage is given by the split between the CB's electron and

Recent progress on quantum dot solar cells: a review

“…7(c). 37,38 These conclusions were further verified by the PL results shown in Fig. 7(d) in which the intensity of QDs emission reduces as the doping increases.…”

“…2.1, for a InAs/GaAs QDSC to be able to reach the same V oc as GaAs SC, the dark saturation current J 0;iþQD must be minimized to the value of J 0;i−GaAs . 38 Jolley et al 77 have addressed this issue by performing both experimental and theoretical studies. As shown in Fig.…”

“…To understand the dark recombination current in QDSC, modeling of the carrier dynamics is indispensable. 6,[36][37][38] A simplified two-voltage region model is proposed by us, as shown in in Figs. 1(a)-1(c).…”

Theoretical model of quantum dot array based intermediate band solar cell: Effect of Sb induced type II alignment on dynamical processes

“…Under the radiativelimit approximation, that might be questionable here, we have estimated the efficiency of such IBSC to be between 24% and 39% for light concentration between 1 and 1000. Analysis of an in-plane coupled InAs/GaAs QD array based IBSC is presented in a separate manuscript [14] Intraband radiative lifetime between electron states e1 and e0 as a function of transition energy between them and Sb concentration in buffer region.…”

Theoretical analysis of GaAs/AlGaAs quantum dots in quantum wire array for intermediate band solar cell

“…However, the band gap combination and the location of IB in InAs/GaAs QD based IBSCs is not favourable and the upper limit efficiency is around 20% (1 sun) and 34% (1000 suns). [3][4][5][6][7] In order to improve the IBSC efficiency, host materials with much wider band gap such as AlGaAs or GaP are required. Recently, we have succeeded in the fabrication of GaAs QD arrays embedded in AlGaAs quantum-wire (QWR) host material by using a combination of neutral beam etching and atomic hydrogen-assisted MBE regrowth.…”