Mode-Selective Tip-Enhanced Raman Spectroscopy Reveals Asymmetric Chemical and Carrier-Sensitive Raman Grading in Photovoltaic III–V Tandem Nanowire Junctions
7 affiliations
- 1Gds-Optronlab, Dpto. Física de la Materia Condensada, Universidad de Valladolid, Paseo de Belén 19, 47011 Valladolid, Spain
- 2Department of Chemistry and Applied Biosciences, ETH Zürich, 8093 Zürich, Switzerland
- 3Nano Lund and Division of Solid-State Physics, Lund University, Box 118, 221 00 Lund, Sweden
- 4Hexagem AB, Ole Römers väg 1H, 223 63 Lund, Sweden
- 5Institute of Microelectronics of Barcelona (IMB−CNM, CSIC), Campus UAB, Bellaterra, 08193, Barcelona, Spain
- 6Wallenberg Initiative Materials Science for Sustainability, Department of Solid-State Physics, Lund University, 221 00 Lund, Sweden
- 7Meeting Life LLC, 1210 Washington Ave. Ste. 213 Miami Beach, Florida 33139, United States
Abstract
Performance of tandem junction nanowire (NW) solar cells relies on the electronic quality of the tunnel diodes which serve as the separating junctions between subcells. Yet, the relevant interfacial physics occurs below the optical diffraction limit. Here we use hyperspectral tip-enhanced Raman spectroscopy (TERS) to map, with nanoscale precision, axially defined heterojunctions in InP/InGaP tandem junction photovoltaic NWs. By resolving mode-specific phonon and phonon–plasmon responses, we show that the nominally abrupt p/p++ and p++/n++ junctions are compositionally graded. The TOM mode, used as the primary compositional marker, yields transition widths of ∼90–120 nm, whereas other lattice- and carrier-sensitive modes exhibit broader central widths up to ∼190 nm, reflecting their additional sensitivity to alloying, structural disorder, and electronic coupling. In a first-order approximation, rescaling these TERS-derived widths to shorter, device-relevant NWs yields narrower junctions, consistent with independent Kelvin probe force microscopy (KPFM) measurements that qualitatively capture the same trend despite surface and tip convolution effects. Complementary equilibrium band-edge model combined with a simplified one-dimensional Wentzel–Kramers–Brillouin (WKB) calculation, as an illustrative trend, further indicates that such grading is expected to widen the effective tunnel barrier. These findings establish mode-selective hyperspectral TERS as a validated, noninvasive method for quantitative nanoscale mapping of compositional grading in III–V NW junctions, with the carrier-sensitive L1 phonon–plasmon response providing complementary, model-assisted insight into the electronic evolution of the junctions.
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BibTeX
@article{hinojosachasiquiza2026modeselective,
title = {{Mode-Selective Tip-Enhanced Raman Spectroscopy Reveals Asymmetric Chemical and Carrier-Sensitive Raman Grading in Photovoltaic III–V Tandem Nanowire Junctions}},
author = {Vanessa Hinojosa-Chasiquiza and Jose Luis Pura and Siiri Bienz and Yue Zhao and Jordi Antoja-Lleonart and Magnus Borgström and Francesc Pérez-Murano and Sergio Muñoz de Baena and Renato Zenobi and Naresh Kumar and Jorge Serrano},
journal = {ACS Nano},
year = {2026},
month = oct,
doi = {10.1021/acsnano.6c10214},
url = {https://doi.org/10.1021/acsnano.6c10214},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Mode-Selective Tip-Enhanced Raman Spectroscopy Reveals Asymmetric Chemical and Carrier-Sensitive Raman Grading in Photovoltaic III–V Tandem Nanowire Junctions
AU - Vanessa Hinojosa-Chasiquiza
AU - Jose Luis Pura
AU - Siiri Bienz
AU - Yue Zhao
AU - Jordi Antoja-Lleonart
AU - Magnus Borgström
AU - Francesc Pérez-Murano
AU - Sergio Muñoz de Baena
AU - Renato Zenobi
AU - Naresh Kumar
AU - Jorge Serrano
PY - 2026
DA - 2026/10/12
JO - ACS Nano
DO - 10.1021/acsnano.6c10214
UR - https://doi.org/10.1021/acsnano.6c10214
AB - Performance of tandem junction nanowire (NW) solar cells relies on the electronic quality of the tunnel diodes which serve as the separating junctions between subcells. Yet, the relevant interfacial physics occurs below the optical diffraction limit. Here we use hyperspectral tip-enhanced Raman spectroscopy (TERS) to map, with nanoscale precision, axially defined heterojunctions in InP/InGaP tandem junction photovoltaic NWs. By resolving mode-specific phonon and phonon–plasmon responses, we show that the nominally abrupt p/p++ and p++/n++ junctions are compositionally graded. The TOM mode, used as the primary compositional marker, yields transition widths of ∼90–120 nm, whereas other lattice- and carrier-sensitive modes exhibit broader central widths up to ∼190 nm, reflecting their additional sensitivity to alloying, structural disorder, and electronic coupling. In a first-order approximation, rescaling these TERS-derived widths to shorter, device-relevant NWs yields narrower junctions, consistent with independent Kelvin probe force microscopy (KPFM) measurements that qualitatively capture the same trend despite surface and tip convolution effects. Complementary equilibrium band-edge model combined with a simplified one-dimensional Wentzel–Kramers–Brillouin (WKB) calculation, as an illustrative trend, further indicates that such grading is expected to widen the effective tunnel barrier. These findings establish mode-selective hyperspectral TERS as a validated, noninvasive method for quantitative nanoscale mapping of compositional grading in III–V NW junctions, with the carrier-sensitive L1 phonon–plasmon response providing complementary, model-assisted insight into the electronic evolution of the junctions.
SN - 1936-0851
SN - 1936-086X
ER -