Chemical beam epitaxy of GaAsN∕GaAs multiquantum well solar cell

Abstract

The authors present preliminary data for a set of GaAsN∕GaAs multiquantum well (MQW) solar cells, grown by radio-frequency (rf) nitrogen plasma-assisted chemical beam epitaxy. The spectral response of this preliminary set of devices extends well below the GaAs band gap, while exhibiting remarkably high photoconversion strength that exceeds that of other MQW-based solar cells with comparable band gaps (1.0–1.2eV). This behavior is consistent with the enhancement of the electron effective mass in III-V dilute nitrides. Although the output current is similar to that of conventional GaInAsN solar cells, the output voltage is significantly higher when compared to that of bulk solar cells of similar wavelengths. The spectral response of as-grown devices is characterized by a deep valley around 1.37–1.4eV, that could be attributed to N contamination of the GaAs barriers. Rapid thermal annealing improves significantly the spectral response in the vicinity of this valley.

Modeling of 1 eV dilute nitride multi-quantum well solar cell

“…3). This unusually strong photoresponse is found to be consistent with previous experimental work [29] on the development of 1.15 eV dilute nitride quantum wells where 15-period 6nm wells of GaAsN with N~1.8% resulted in quantum efficiencies in excess of 50% for the MQW region. The efficiency of this structure as incorporated into the intrinsic region of the GaAs sub-cell (behind the GaAs sub-cell of a multi-junction InGaP/GaAs/Ge solar cell) was then calculated by current matching.…”

InGaAs/GaAs MQWs: Correlation of crystal and physical properties

“…Experimental studies on MQW solar cells absorbing above 1.1-1.2 e V include sub-cells composed of InGaAs/GaAs [4] and GaAsN/GaAs compounds [5], proving accessibility of growth conditions for lattice-matched growth and strong optical absorption by the incorporated MQW nanostructures. However, device designers aiming for better performance need to correlate physical properties of the grown material with the growth conditions and crystal perfection of epitaxial structures under which desired physical properties are achieved.…”

Resonant thermo-tunneling design for ultra-efficient nanostructured solar cells

“…Materials of nano-metric sizes embedded in the active region of organic or inorganic solar cell matrices have been theoretically shown to overcome photo-conversion efficiency limitations of their bulk counterparts [4][5][6][7][8] . In particular, device concepts where such nanostructures form part of the absorbing medium present possibilities of achieving ultrahigh photo-conversion efficiencies well in excess of 50%.…”