Optical spectrum of bottom-up graphene nanoribbons: towards efficient atom-thick excitonic solar cells

TL;DR

This study uses advanced computational methods to analyze the electronic and optical properties of bottom-up synthesized graphene nanoribbons, highlighting their potential for efficient atom-thick excitonic solar cells.

Contribution

It provides a detailed ab-initio analysis of the optical properties of cove-shaped graphene nanoribbons, emphasizing the importance of electron-hole interactions for accurate predictions.

Findings

Excitonic effects are crucial for understanding optical spectra.

Excitonic peaks involve transitions between first and second conduction and valence bands.

Nanoribbons show promise as donor materials in photovoltaic devices.

Abstract

Recently, atomically well-defined cove-shaped graphene nanoribbons have been obtained using bottom-up synthesis. These nanoribbons have an optical gap in the visible range of the spectrum which make them candidates for donor materials in photovoltaic devices. From the atomistic point of view, their electronic and optical properties are not clearly understood. Therefore, in this work we carry out ab-initio density functional theory calculations combine with many-body perturbation formalism to study their electronic and optical properties. Through the comparison with experimental measurements, we show that an accurate description of the nanoribbon's optical properties requires the inclusion of electron-hole correlation effects. The energy, binding energy and the corresponding excitonic transitions involved are analyzed. We found that in contrast to zigzag graphene nanoribbons, the excitonic peaks in the absorption spectrum are a consequence of a group of transitions involving the first and second conduction and valence bands. Finally, we estimate some relevant optical properties that strengthen the potential of these nanoribbons for acting as a donor materials in photovoltaic.