Energy Upconversion in GaP/GaNP Core/Shell Nanowires for Enhanced Near-Infrared Light Harvesting
2014 (English)In: Small, ISSN 1613-6810, E-ISSN 1613-6829, Vol. 10, no 21, 4403-4408 p.Article in journal (Refereed) Published
Semiconductor nanowires (NWs) have recently gained increasing interest due to their great potential for photovoltaics. A novel material system based on GaNP NWs is considered to be highly suitable for applications in efficient multi-junction and intermediate band solar cells. This work shows that though the bandgap energies of GaNx P1-x alloys lie within the visible spectral range (i.e., within 540-650 nm for the currently achievable x < 3%), coaxial GaNP NWs grown on Si substrates can also harvest infrared light utilizing energy upconversion. This energy upconversion can be monitored via anti-Stokes near-band-edge photoluminescence (PL) from GaNP, visible even from a single NW. The dominant process responsible for this effect is identified as being due to two-step two-photon absorption (TS-TPA) via a deep level lying at about 1.28 eV above the valence band, based on the measured dependences of the anti-Stokes PL on excitation power and wavelength. The formation of the defect participating in the TS-TPA process is concluded to be promoted by nitrogen incorporation. The revealed defect-mediated TS-TPA process can boost efficiency of harvesting solar energy in GaNP NWs, beneficial for applications of this novel material system in third-generation photovoltaic devices.
Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2014. Vol. 10, no 21, 4403-4408 p.
nanowires; optical properties; photoluminescence; solar cells; upconversion
Condensed Matter Physics
IdentifiersURN: urn:nbn:se:liu:diva-109929DOI: 10.1002/smll.201401342ISI: 000344903500023PubMedID: 25045136OAI: oai:DiVA.org:liu-109929DiVA: diva2:741665