This document discusses the luminescent properties of hexagonal boron nitride (h-BN) monolayers and bulk. It first introduces h-BN as a layered material similar to graphite that is transparent with a large bandgap and can emit ultraviolet light. Studies have found that bulk h-BN exhibits strong phonon-assisted luminescence due to exciton localization, while monolayer h-BN only shows direct light emission with weak phonon-assisted transitions. Recent work developed a new theoretical approach to study phonon-assisted transitions in solids, validating the theory through comparison to experimental luminescence spectra of both bulk and monolayer h-BN.

1. Luminescence of
hexagonal boron nitride monolayer
Claudio Attaccalite
P. Lechifflart, F. Paleari,
D. Sangalli
Advanced Quantum Materials (2023)

2. Hexagonal Boron Nitride
h-BN is a layered
crystal homo-structural to
graphite.
As graphite, h-BN can be
easily exfoliated, and for this
reason it finds applications
as lubricant .

3. Use of hBN in condensed matter
Encapsulated 2D materials
Single
photon
emitters

4. Hexagonal Boron Nitride
h-BN has a large band
gap and it’s transparent
h-BN emits light in
the ultraviolet

5. UV light emitters

6. Band structure of hBN

7. Internal quantum yield
0.1%
ZnO Diamond
50%
Bright Luminescence from Indirect and Strongly Bound Excitons in h-BN
L. Schué, L. Sponza et al.,
Phys. Rev. Lett. 122, 067401(2019)

8. Internal quantum yield
45%
0.1%
ZnO Diamond
hBN
50%
Bright Luminescence from Indirect and Strongly Bound Excitons in h-BN
L. Schué, L. Sponza et al.,
Phys. Rev. Lett. 122, 067401(2019)

9. Strong bound
excitons in h-BN
Ellipsometry Study of Hexagonal Boron
Nitride Using Synchrotron Radiation:
Transparency Window in the Far‐UVC
Luis Artús, et al. Advanced Photonics
Research 2 (5), 2000101 (2021)
No-exciton
spectrum

10. The strong exciton confinement
enhances the coupling with phonons
Exciton-phonon coupling
Theory of phonon-assisted luminescence in solids:
application to hexagonal boron nitride
E. Cannuccia,et al. Phys. Rev. B 99, 081109(R) (2019)

11. Monolayer hexagonal BN
First Luminescence measurement on epitaxial grown
monolayer boron nitride on graphite substrates
Nature Communications volume 10, Article number: 2639 (2019)

12. From bulk to monolayer…..
Direct observation of the band structure in bulk hexagonal boron nitride
H. Henck, et al.
PRB 95, 085410(2017)

13. Luminescence spectra
Nature Communications volume 10, Article number: 2639 (2019)

14. Luminescence spectra … again
Monolayer Boron Nitride: Hyperspectral Imaging in the
Deep Ultraviolet
A. Rousseau et al.
Nano Lett. 2021, 21, 23, 10133–10138

15. Luminescence spectra … again
Monolayer Boron Nitride: Hyperspectral Imaging in the
Deep Ultraviolet
A. Rousseau et al.
Nano Lett. 2021, 21, 23, 10133–10138
“Scalable Synthesis of Monolayer Hexagonal Boron
Nitride on Graphene with Giant Bandgap
Renormalization."
Wang et al. Advanced Materials 34.21 (2022).

16. A new theoretical approach

17. Validation

18. Theory vs experiments

19. Conclusion
●
Strong phonon assisted luminescence of bulk BN is due
to the exiciton localization
●
Monolayer-BN presents only direct light-emission, the
phonon assisted one is too weak
●
We developed a new approach to study phonon-assisted
transitions

Theory of phonon-assisted luminescence in solids: application to hexagonal boron nitride
E. Cannuccia,et al. Phys. Rev. B 99, 081109(R) (2019)

Ellipsometry Study of Hexagonal Boron Nitride Using Synchrotron Radiation: Transparency
Window in the Far‐UVC, Luis Artús, et al. Advanced Photonics Research 2 (5), 2000101 (2021)
●
First-principles study of luminescence in hexagonal boron nitride single layer: Exciton-phonon
coupling and the role of substrate
P. Lechifflart, et al. Phys. Rev. Mat. 7, 024006 (2023)

20. Direct or
indirect excitons

21. The role of substrate