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Energy Bands in Solids

Energy Bands in Solids

Isolated atoms have discrete energy levels that are well described by the Bohr model. And, it quantifies the energy of an electron in a hydrogen atom as En. Higher quantum numbers 'n' yield less negative, closer electron energy levels.
Band Formation:
When atoms are brought close together, as in a solid, these discrete energy levels begin to split due to the overlap of electron orbitals from adjacent atoms. This split occurs because of the Pauli exclusion principle, which states...

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Updated: Sep 22, 2025

Probe Type II Band Alignment in One-Dimensional Van Der Waals Heterostructures Using First-Principles Calculations

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Published on: October 12, 2019

Manipulation of Band Alignment in Two-Dimensional Vertical WSe₂/BA₂PbI₄ Ruddlesden-Popper Perovskite Heterojunctions

Junmin Xia¹, Hao Gu¹, Chao Liang¹

¹Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macau 999078, P. R. China.

The Journal of Physical Chemistry Letters

|May 18, 2022

Summary

Defect engineering in WSe2/BA2PbI4 heterojunctions allows tuning of band alignment for optoelectronic applications. Vacancies can switch interfaces, enhancing carrier separation or recombination.

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Last Updated: Sep 22, 2025

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Published on: September 8, 2017

Area of Science:

Materials Science
Condensed Matter Physics
Nanotechnology

Background:

Two-dimensional (2D) materials like transition metal dichalcogenides (TMDs) and Ruddlesden-Popper perovskites are crucial for optoelectronics.
Understanding interface band alignment and defect engineering in TMD/perovskite heterojunctions is vital but underexplored.

Purpose of the Study:

Investigate optoelectronic properties and defect engineering of WSe2/BA2PbI4 heterojunctions.
Explore how defect modulation impacts band alignment and carrier dynamics.

Main Methods:

Utilized density functional theory (DFT) simulations.
Analyzed WSe2/BA2PbI4 van der Waals heterojunction properties.
Simulated the effects of specific vacancies (BA and Se) on band alignment.

Main Results:

The pristine WSe2/BA2PbI4 heterojunction exhibits an indirect bandgap and S-scheme alignment, promoting efficient charge separation.
Introducing BA vacancies shifts the band alignment from S-scheme to type II.
Se vacancies enhance recombination at the S-scheme interface.

Conclusions:

Interfacial properties of TMD/perovskite heterojunctions can be precisely controlled through defect engineering.
This control enables tailoring heterojunctions for diverse optoelectronic applications.