Drift‐diffusion model for intermediate band solar cells including photofilling effects

Abstract

A novel drift-diffusion model for intermediate band solar cells (IBSC) is presented. The model differs from previous driftdiffusion models by allowing the carrier concentrations in all three bands to vary. It is developed for the idealized case where only radiative recombination occurs and where the IB has zero width. The model is used to compare the performance of IBSCs where the IB-region is doped to get a partially filled IB (prefilled IBSC) to IBSCs where the IB-region is not doped to partially fill the IB (photofilled IBSC). Numerical results show that a photofilled IBSC can achieve high efficiencies when operated under concentrated light. In fact, for some particular cases, a photofilled cell will perform better than a prefilled cell. The optimal degree of prefilling, i.e. the ratio of the concentration of doping atoms to the total number of IB-states, is found for a particular example. It is also examined how the carrier concentrations in all three bands, the conduction, the intermediate and the valence bands, vary in prefilled and photofilled IBSCs. Finally, the band diagrams of a prefilled and photofilled IBSC are discussed.

Understanding the operation of quantum dot intermediate band solar cells

“…The sum of these two voltages is the applied voltage V and provides a VðJ QD Þ relationship that is inverted numerically to obtain J QD ðVÞ. Thus, the total current in the QD zone is J IB ðVÞ ¼ J QD ðVÞ þ J lhi ðVÞ þ J scz ðVÞ þ J radCV ðVÞ: (16) VI. DISCUSSION Figure 6 shows the measured 32 values of the J L -V OC curves for the test solar cell and the IB solar cell at different temperatures, together with the fitted curves.…”

“…11 Several papers have modeled the operation of an intermediate band solar cell including drift-diffusion mechanisms. [14][15][16][17] The purpose of this paper is to model the measured low temperature behavior by using the standard knowledge of device physics. This will help us to better understand this device and ways of improving it.…”

Self-formation of ultrahigh-density (1012 cm−2) InAs quantum dots on InAsSb/GaAs(001) and their photoluminescence properties

“…In particular, intermediate-band solar cells (IBSCs) have a high power conversion efficiency and could represent the next generation of solar devices. 1) Using a detailed balance model, 2,3) we have recently calculated the QD density dependence of IBSCs based on InAs QDs on GaAsSb. 4) A total QD density of 3 × 10 13 cm −2 is required to have a high-power conversion efficiency of at least 40% under concentrated sunlight.…”

Effect of Si doping and sunlight concentration on the performance of InAs/GaAs quantum dot solar cells

“…Furthermore, nonradiative recombination processes were not considered and the overlap of absorption coefficients among various transitions was also assumed ideal as zero. [20][21][22] The simulated I SC as given by J SC normalized by X, V OC , and cell efficiency are plotted as a function of sunlight concentration ratio X for IBSCs and for single-junction GaAs reference SC as shown in Figs. 2(a) through 2(c), respectively.…”

“…Martí et al 9 and the works that follow [12][13][14][15][16][17][18][19] have employed the modulation-doping technique to fabricate QD-IBSCs, in which each GaAs barrier/spacer layer was delta (δ)-doped with Si with a sheet density equal to or larger than the InAs QDs areal density. On the other hand, Strandberg and Reenaas 20 have performed a simulation and have shown that under radiative limit, IB must be partially filled by means of doping within a reasonable optical length to achieve high efficiency if QD-IBSCs were to be operated under one sun condition. It would, however, become possible to sustain a reasonable population of photogenerated electrons even in a nondoped QD-IBSC under concentrated sunlight, typically 100 to 1000 suns.…”