Tuning electronic and optical properties of 2D polymeric C$_{60}$ by stacking two layers

TL;DR

This study systematically compares the structural, electronic, and optical properties of monolayer and bilayer polymeric C$_{60}$, revealing how stacking influences their potential for photocatalysis and photovoltaics.

Contribution

It provides a comprehensive theoretical analysis of how stacking two layers of C$_{60}$ alters their electronic and optical properties, offering strategies to tune these properties for applications.

Findings

Bilayer C$_{60}$ maintains similar band gap and band-edge positions as monolayer.

Bilayer exhibits enhanced exciton absorption across visible light range.

Interlayer interactions increase optical anisotropy and polarization dependence.

Abstract

Benefiting from improved stability due to stronger interlayer van der Waals interactions, few-layer fullerene networks are experimentally more accessible compared to monolayer polymeric C$_{60}$. However, there is a lack of systematic theoretical studies on the material properties of few-layer C$_{60}$ networks. Here, we compare the structural, electronic and optical properties of bilayer and monolayer fullerene networks. The band gap and band-edge positions remain mostly unchanged after stacking two layers into a bilayer, enabling the bilayer to be almost as efficient a photocatalyst as the monolayer. The effective mass ratio along different directions is varied for conduction band states due to interlayer interactions,leading to enhanced anisotropy in carrier transport. Additionally, stronger exciton absorption is found in the bilayer than that in the monolayer over the entire visible light range, rendering the bilayer a more promising candidate for photovoltaics. Moreoever, the polarisation dependence of optical absorption in the bilayer is increased in the red-yellow light range, offering unique opportunities in photonics and display technologies with tailored optical properties over specific directions. Our study provides strategies to tune electronic and optical properties of 2D polymeric C$_{60}$ via the introduction of stacking degrees of freedom.