Revolutionary assembly of 2D molecular structures can boost solar cell performance

By Ashwini Sakharkar 1 Oct, 2024

Collected at: https://www.techexplorist.com/revolutionary-assembly-2d-molecular-structures-boost-solar-cell-performance/90572/

The cutting-edge realm of material science and electronics hinges on the ingenious manipulation of molecules and atoms to engineer materials with extraordinary properties that defy the norms of conventional materials. Enter the realm of two-dimensional (2D) assemblies of π-electronic systems delicately arranged in thin layers, which are swiftly gaining eminence in the domains of materials science and organic electronics.

Their distinctive configuration bestows them with tailored electronic and physical properties, rendering them perfect for applications such as solar cells and flexible displays. Yet, the creation of such assemblies poses a formidable challenge, often necessitating bespoke designs and techniques for each molecule type.

However, a study published in Science Advances by Assistant Professor Tomoya Fukui and Professor Takanori Fukushima from the Institute of Science Tokyo, in collaboration with Professor Taku Hasobe from Keio University, introduces a game-changing approach utilizing supramolecular scaffolds.

These scaffolds act as molecular blueprints, enabling the assembly of diverse molecules into 2D structures without the need for custom setups for each component. This breakthrough promises to revolutionize the landscape of material science and electronics, paving the way for unprecedented advancements in the field.

The researchers utilized a remarkable 1,8,13-substituted tripodal triptycene as a supramolecular scaffold. This extraordinary scaffold has the ability to assemble into a captivating 2D hexagonal pattern, which can then be stacked along one dimension, creating a mesmerizing “2D + 1D” structure. The intriguing space between these layers offers accommodation for other molecules.

In their pioneering work, the team ingeniously incorporated spherical fullerene (C60) molecules within these layers. Building upon this, their latest study showcases the scaffold’s capability to elegantly organize planar acene chromophores. By sandwiching pentacene and anthracene chromophores between two triptycene units, they have ingeniously formed two distinct 2D self-assembling structures.

The choice of acenes was deliberate, as they possess significant potential for singlet fission (SF). This exceptional process entails the transformation of a single high-energy photon into two lower-energy triplet excitons, which is anticipated to significantly enhance solar cell efficiency by facilitating the generation of more charge carriers.

Dr. Fukui notes that for efficient singlet fission in the solid state, two conditions must be met: “Acene chromophores need to be placed in close proximity to each other to provide sufficient electronic coupling. Second, the environment around the chromophores needs to be designed to allow them to undergo conformational changes to prevent triplet recombination.”

In the realm of pentacene-based assemblies, the remarkable overlap of chromophores has unlocked the potential for singlet fission, boasting an impressive quantum yield of 88% for yielding a pair of triplets and a staggering 130% for generating two free triplets. Conversely, the anthracene-based assemblies have failed to demonstrate singlet fission, possibly due to the lack of robust electronic coupling between the chromophores.

“Pentacene chromophores, which have a size larger than that of the diameter of the triptycene framework, have effective overlap to cause SF, while such an overlap between the chromophores does not occur in the assembly of anthracene analog,” explains Prof. Fukushima.

Such assemblies can be integrated into comb-shaped electrodes, potentially paving to the way for device applications. “This demonstrates the utility of the triptycene-based supramolecular scaffold to design functional pi-electronic molecular assemblies,” says Prof. Hasobe.

This adaptable scaffold design serves as a versatile platform for crafting 2D assemblies using an array of molecules, heralding a new era of progress in supramolecular chemistry, materials science, and organic electronics.

Journal reference:

1. Masato Fukumitsu, Tomoya Fukui, Yoshiaki Shoji, Takashi Kajitani, Ramsha Khan, Nikolai V. Tkachenko, Hayato Sakai, Taku Hasobe, Takanori Fukushima. Supramolecular scaffold–directed two-dimensional assembly of pentacene into a configuration to facilitate singlet fission. Science Advances, 2024; DOI: 10.1126/sciadv.adn7763