Lattice‐matched four‐junction tandem solar cell including two dilute nitride bottom junctions

Abstract

Monolithic four-junction solar cells incorporating two dilute nitride (GaInNAsSb) bottom junctions are reported. The dilute nitride junctions have band gaps of 0.9 and 1.2 eV, while the top junctions have band gaps of 1.4 and 1.9 eV. By using experimental-based parametrization, it was estimated that the four-junction solar cell could theoretically exhibit efficiency levels of 34.7% at one sun, 43.2% at 100 suns, and 46.4% at 1000 suns for AM1.5D illumination. The most challenging subcell in terms of fabrication is the GaInNAsSb bottom junction with 0.9 eV band gap. For this subcell, a background doping level down to 5 × 10 14 cm −3 and a high charge carrier lifetime up to 2 to 4 nanoseconds are reported, which reflects high values for current and voltage. An experimental AlGaAs/GaAs/GaInNAsSb/GaInNAsSb solar cell structure was fabricated by molecular beam epitaxy. At one-sun AM1.5D illumination, the experimental cell exhibited an efficiency of 25%, an average quantum efficiency of 91%, and an open circuit voltage, which is about 87% of the estimated potential.The cell exhibited maximum efficiency of 37% at 100-sun concentration.

Wide spectral coverage (0.7–2.2 eV) lattice‐matched multijunction solar cells based on AlGaInP, AlGaAs and GaInNAsSb materials

“…The performance of the LM 4J solar cell was modeled using simple diode equations that have been earlier validated for dilute nitride-based 3J and 4J solar cells. 8…”

“…To this end, an upright LM 4J GaInP/GaAs/GaInNAsSb/GaInNAsSb solar cell monolithically grown on GaAs by molecular beam epitaxy (MBE) was reported recently. 8 This first demonstration of 4J design including two dilute nitride subcells, which is schematically shown in Figure 1, exhibited an efficiency of 25% at one-sun illumination, whereas an efficiency of 37% was already demonstrated under 100-sun illumination. It was also estimated that efficiency of 47% seems feasible under higher concentration for an optimized design.…”

“…Upright III-V triple-junction (3J) solar cells have been fabricated for more than a decade, [2][3][4] and recently, also 4J solar cells have been reported with metamorphic 2 and LM approaches. [5][6][7][8] The upright LM approach is particularly interesting, because besides the fact that it avoids the use of metamorphic buffer layers, it can make use of the same tunnel junctions that have been long time optimized for the LM 3J solar cells. Moreover, the LM approach is the most efficient strategy in terms of material utilization given their reduced thickness, a feature that becomes more evident for architectures with four or more subcells.…”

Characterization of Plasmonic Scattering, Luminescent Down-Shifting, and Metal-Enhanced Fluorescence and Applications on Silicon Solar Cells

“…Materials must be selected carefully to minimize mismatch between the solar spectrum and the spectral absorption of solar cell (spectral losses). One approach to expand the usable range of light involves the application of a conversion layer, such as down conversion (DC) [18,19], down shifting (DS) [20,21], up conversion (UC) [22,23], and multi-junction tandem structures [24,25]. DC involves converting an incident high-energy photon (UV-blue wavelengths) into two or more photons of lower energy (within visible wavelengths).…”

Structures based on GaAs(Sb)(N) semiconductor alloys for high efficiency multi-junction solar cells

“…However, these efficiency values are still well below the theoretical limit, which for concentrator devices overcome 50 %: epitaxial growth and material quality problems inherent to quaternary and quinary dilute nitride alloys lead to low carrier mobility and short diffusion length [50], seriously affecting carrier dynamics [45,51,52]. Despite the intense activity of many groups and some relevant advances [53][54][55][56][57][58][59][60], no improvements in conversion efficiency with three-or four-junction cells have been certified since 2015 [4], and solar cell performance above the 50 % has not been achieved so far [61].…”