Periodic Reporting for period 1 - TECTESA (Tuning Exciton diffusion through Charge-Transfer Excitations in Supramolecular Assemblies)
Période du rapport: 2023-10-01 au 2025-09-30
The transition toward a sustainable, low-carbon economy is a central priority of the European Union, as reflected in the European Green Deal and Horizon Europe’s objectives for clean energy and advanced materials. Meeting these goals requires the development of innovative materials capable of efficiently harvesting and converting solar energy while remaining cost-effective and environmentally friendly. In this context, organic materials have emerged as a promising alternative to traditional inorganic semiconductors. They can be processed at low temperatures, are lightweight and flexible, and allow for chemical tailoring of their properties, making them ideal for next-generation photovoltaic and optoelectronic technologies such as organic solar cells and light-emitting diodes.
Despite this promise, the performance of organic-based devices still lags behind inorganic counterparts. A key limitation lies in the incomplete understanding of how energy and charge are transported within these materials. Organic semiconductors are composed of discrete molecules bound by weak non-covalent interactions, which means that their electronic states are often localized and strongly coupled to molecular vibrations and structural disorder. Unlike crystalline inorganic solids, where electrons move freely through periodic lattices, transport in organic systems is inherently dynamic and influenced by molecular motion. This complexity makes it difficult to predict or optimize the efficiency of energy and charge migration, which directly affects device performance.
Addressing this gap requires a theoretical framework capable of linking molecular structure and organization to the macroscopic properties observed experimentally. The TECTESA project (Theoretical Characterization of Energy and Charge Transport in Supramolecular Aggregates) was designed to tackle this fundamental challenge. Its overarching goal was to provide a unified theoretical understanding of excitonic and charge transport in organic materials by identifying how structural and electronic parameters control energy migration and optical response. Through the study of representative organic crystals and supramolecular aggregates, the project aimed to establish general design principles that guide the development of materials with enhanced transport properties.
TECTESA builds upon the recognition that excitons — bound electron-hole pairs generated upon light absorption — play a central role in the operation of organic devices. Their ability to migrate efficiently determines the performance of solar cells, light-emitting devices, and other optoelectronic components. However, exciton transport depends sensitively on the degree of electronic coupling between molecules, the presence of dynamic disorder, and the strength of vibronic interactions. Understanding how these factors interact requires simulations and theoretical analyses that capture the balance between electronic delocalization and vibrational effects.
The project addressed this challenge by employing atomistic and semiclassical models to investigate how microscopic features — such as molecular packing, electronic couplings, and vibrational reorganization energies — influence exciton mobility and optical spectra. By systematically exploring a broad range of conditions, TECTESA aimed to identify the transition regimes between coherent, incoherent, and mixed transport behavior, and to define the structural motifs that promote efficient energy transfer. These insights enable the formulation of general rules that can be applied across different families of organic materials, extending beyond specific chemical systems to provide predictive guidelines for molecular design.
Ultimately, the project provides not only new scientific insights but also a conceptual framework to guide future research. By elucidating the key parameters governing exciton and charge migration, TECTESA contributes to the rational design of materials that can accelerate Europe’s transition toward sustainable and high-performance optoelectronic technologies.
Despite this promise, the performance of organic-based devices still lags behind inorganic counterparts. A key limitation lies in the incomplete understanding of how energy and charge are transported within these materials. Organic semiconductors are composed of discrete molecules bound by weak non-covalent interactions, which means that their electronic states are often localized and strongly coupled to molecular vibrations and structural disorder. Unlike crystalline inorganic solids, where electrons move freely through periodic lattices, transport in organic systems is inherently dynamic and influenced by molecular motion. This complexity makes it difficult to predict or optimize the efficiency of energy and charge migration, which directly affects device performance.
Addressing this gap requires a theoretical framework capable of linking molecular structure and organization to the macroscopic properties observed experimentally. The TECTESA project (Theoretical Characterization of Energy and Charge Transport in Supramolecular Aggregates) was designed to tackle this fundamental challenge. Its overarching goal was to provide a unified theoretical understanding of excitonic and charge transport in organic materials by identifying how structural and electronic parameters control energy migration and optical response. Through the study of representative organic crystals and supramolecular aggregates, the project aimed to establish general design principles that guide the development of materials with enhanced transport properties.
TECTESA builds upon the recognition that excitons — bound electron-hole pairs generated upon light absorption — play a central role in the operation of organic devices. Their ability to migrate efficiently determines the performance of solar cells, light-emitting devices, and other optoelectronic components. However, exciton transport depends sensitively on the degree of electronic coupling between molecules, the presence of dynamic disorder, and the strength of vibronic interactions. Understanding how these factors interact requires simulations and theoretical analyses that capture the balance between electronic delocalization and vibrational effects.
The project addressed this challenge by employing atomistic and semiclassical models to investigate how microscopic features — such as molecular packing, electronic couplings, and vibrational reorganization energies — influence exciton mobility and optical spectra. By systematically exploring a broad range of conditions, TECTESA aimed to identify the transition regimes between coherent, incoherent, and mixed transport behavior, and to define the structural motifs that promote efficient energy transfer. These insights enable the formulation of general rules that can be applied across different families of organic materials, extending beyond specific chemical systems to provide predictive guidelines for molecular design.
Ultimately, the project provides not only new scientific insights but also a conceptual framework to guide future research. By elucidating the key parameters governing exciton and charge migration, TECTESA contributes to the rational design of materials that can accelerate Europe’s transition toward sustainable and high-performance optoelectronic technologies.
The TECTESA project set out to understand how energy moves through organic materials — a key step in creating the next generation of flexible and sustainable technologies such as organic solar cells and light-emitting devices. These materials are made of individual molecules that self-assemble into ordered structures held together by weak, non-covalent forces. Because their components are soft and dynamic, energy and charge move through them in a far more complex way than in conventional semiconductors such as silicon. The project’s main goal was to uncover the microscopic rules that determine how efficiently this energy can travel, and how molecular structure and motion influence the process.
Throughout the fellowship, Dr. Jesús Cerdá combined state-of-the-art computational chemistry and theoretical physics to follow the journey of electronic excitations—known as excitons—across different types of organic materials. These excitons are created when light is absorbed and are responsible for transferring the absorbed energy to regions where it can be converted into electricity or re-emitted as light. Understanding how far and how fast they can move is crucial for improving device performance.
The research began by studying how the way molecules pack together affects their ability to share electronic energy. Using atomistic models of representative organic crystals and supramolecular aggregates, the project explored how slight variations in stacking, molecular orientation, or distance modify the strength of electronic coupling between neighboring molecules. This analysis revealed that even small structural changes can drastically alter the pathways through which energy flows, highlighting the importance of controlling molecular organization during material fabrication.
TECTESA then examined how this molecular organization translates into measurable optical properties. By simulating how the materials absorb and emit light, the project established direct links between the microscopic arrangement of molecules and the color, intensity, and efficiency of their optical response. These results contribute to explaining why certain materials behave as efficient light harvesters or bright emitters, while others with similar compositions perform poorly.
A central achievement of the project was clarifying how molecular vibrations and dynamic disorder influence energy transport. In soft organic materials, atoms are constantly moving, and these vibrations can either assist or hinder the migration of excitons. The simulations performed in TECTESA demonstrated that a moderate level of molecular motion can actually enhance energy transport by temporarily delocalizing the excitation across several molecules. Conversely, strong disorder or overly flexible structures tend to localize the excitation, slowing down or even trapping the energy. This finding provides valuable guidelines for designing materials that strike the right balance between rigidity and flexibility to achieve optimal performance.
By exploring a wide range of conditions, the project was able to identify different regimes of energy transport—from coherent, wave-like motion where the excitation spreads rapidly, to incoherent, hopping-like motion dominated by disorder. The results showed that most realistic materials operate in an intermediate regime where both behaviors coexist, and where fine control of molecular packing and vibration is essential to tune performance. This unified picture offers a conceptual bridge between the quantum-mechanical and classical descriptions of transport, helping to rationalize diverse experimental observations within a single theoretical framework.
Overall, TECTESA provided a clearer and more general understanding of how microscopic molecular interactions give rise to macroscopic optical and transport properties in organic materials. The insights gained establish guiding principles for the rational design of more efficient and sustainable optoelectronic materials. Beyond advancing fundamental knowledge, the outcomes of TECTESA contribute to the broader European effort to develop clean and low-impact technologies, supporting the goals of the Green Deal and Horizon Europe.
The project’s findings have been disseminated through scientific publications, conference presentations, and open-access resources, ensuring that the knowledge generated is available to the wider research community and industry. In doing so, TECTESA has strengthened Europe’s leadership in the theoretical understanding of organic materials and has paved the way for new advances in energy-efficient and environmentally friendly technologies.
Throughout the fellowship, Dr. Jesús Cerdá combined state-of-the-art computational chemistry and theoretical physics to follow the journey of electronic excitations—known as excitons—across different types of organic materials. These excitons are created when light is absorbed and are responsible for transferring the absorbed energy to regions where it can be converted into electricity or re-emitted as light. Understanding how far and how fast they can move is crucial for improving device performance.
The research began by studying how the way molecules pack together affects their ability to share electronic energy. Using atomistic models of representative organic crystals and supramolecular aggregates, the project explored how slight variations in stacking, molecular orientation, or distance modify the strength of electronic coupling between neighboring molecules. This analysis revealed that even small structural changes can drastically alter the pathways through which energy flows, highlighting the importance of controlling molecular organization during material fabrication.
TECTESA then examined how this molecular organization translates into measurable optical properties. By simulating how the materials absorb and emit light, the project established direct links between the microscopic arrangement of molecules and the color, intensity, and efficiency of their optical response. These results contribute to explaining why certain materials behave as efficient light harvesters or bright emitters, while others with similar compositions perform poorly.
A central achievement of the project was clarifying how molecular vibrations and dynamic disorder influence energy transport. In soft organic materials, atoms are constantly moving, and these vibrations can either assist or hinder the migration of excitons. The simulations performed in TECTESA demonstrated that a moderate level of molecular motion can actually enhance energy transport by temporarily delocalizing the excitation across several molecules. Conversely, strong disorder or overly flexible structures tend to localize the excitation, slowing down or even trapping the energy. This finding provides valuable guidelines for designing materials that strike the right balance between rigidity and flexibility to achieve optimal performance.
By exploring a wide range of conditions, the project was able to identify different regimes of energy transport—from coherent, wave-like motion where the excitation spreads rapidly, to incoherent, hopping-like motion dominated by disorder. The results showed that most realistic materials operate in an intermediate regime where both behaviors coexist, and where fine control of molecular packing and vibration is essential to tune performance. This unified picture offers a conceptual bridge between the quantum-mechanical and classical descriptions of transport, helping to rationalize diverse experimental observations within a single theoretical framework.
Overall, TECTESA provided a clearer and more general understanding of how microscopic molecular interactions give rise to macroscopic optical and transport properties in organic materials. The insights gained establish guiding principles for the rational design of more efficient and sustainable optoelectronic materials. Beyond advancing fundamental knowledge, the outcomes of TECTESA contribute to the broader European effort to develop clean and low-impact technologies, supporting the goals of the Green Deal and Horizon Europe.
The project’s findings have been disseminated through scientific publications, conference presentations, and open-access resources, ensuring that the knowledge generated is available to the wider research community and industry. In doing so, TECTESA has strengthened Europe’s leadership in the theoretical understanding of organic materials and has paved the way for new advances in energy-efficient and environmentally friendly technologies.
Results Beyond the State of the Art
Before the TECTESA project, theoretical studies of energy transport in organic materials were often based on simplified or static models that could not fully capture the complexity of real systems. These materials are composed of individual molecules interacting through weak forces, and their energy transport is governed by a delicate balance between electronic coupling, molecular vibrations, and structural disorder. Traditional models typically described only one of these aspects at a time, providing a fragmented and sometimes contradictory picture. As a result, researchers lacked general rules to predict how microscopic molecular arrangements determine macroscopic optical and transport properties.
TECTESA has advanced the state of the art by providing a unified theoretical understanding of how excitons—quasiparticles responsible for energy transfer—move through organic materials. By integrating atomistic-level information with semiclassical simulations, the project connected molecular packing, electronic structure, and dynamic fluctuations into a coherent framework capable of explaining and predicting exciton behavior under realistic conditions. This represents a significant conceptual step forward: instead of treating exciton motion as purely coherent (wave-like) or incoherent (hopping-like), TECTESA demonstrated that most organic materials operate in an intermediate, mixed regime where both mechanisms coexist. This insight reconciles previously inconsistent experimental observations and defines a continuum of transport behaviors determined by the relative strength of molecular coupling and vibronic interactions.
One of the key results of TECTESA was the identification of clear structure–property relationships that link molecular arrangement and electronic coupling to exciton delocalization and mobility. The project showed that specific packing motifs—such as slip-stacked or two-dimensional herringbone arrangements—promote partial delocalization, enabling energy to travel more efficiently through the material. Conversely, excessive disorder or strong vibronic coupling leads to localization, reducing transport efficiency. These findings allow researchers to predict, at a design stage, how a given molecular organization will perform, enabling more rational approaches to material synthesis and device engineering.
Another important contribution lies in the quantitative analysis of how molecular vibrations assist or hinder energy transfer. The project revealed that certain vibrational modes can dynamically enhance coupling between molecules, temporarily extending exciton coherence and improving mobility. This effect provides a physical explanation for the high diffusion lengths observed in some organic semiconductors and suggests that controlling vibrational dynamics—through molecular rigidity or chemical substitution—can be an effective strategy to optimize performance.
By establishing these general principles, TECTESA has provided the theoretical foundation for a predictive approach to organic material design. Its results are not limited to specific systems but can be extended to a wide range of soft and hybrid materials, including covalent organic frameworks (COFs), perovskite–organic composites, and molecular aggregates used in light-harvesting or sensing applications. The framework developed during the project can help identify the optimal balance between order and flexibility needed to maximize energy and charge transport, guiding both academic research and industrial innovation.
Potential Impact and Future Needs
The scientific insights from TECTESA have strong potential to influence how organic optoelectronic materials are designed and optimized. By providing clear design rules linking molecular packing to energy transport efficiency, the project can accelerate the discovery of materials for sustainable technologies such as organic photovoltaics, light-emitting diodes, and photodetectors. These applications directly contribute to the European Green Deal objectives of clean energy, circular materials, and reduced environmental impact.
To translate these scientific results into technological progress, several steps are needed. Further research should focus on integrating the theoretical insights into multiscale models that connect molecular behavior with full device performance. Collaboration with experimental and industrial partners will be essential to validate the predicted structure–property relationships and to identify synthetic strategies capable of achieving the optimal molecular arrangements identified by TECTESA.
For broader uptake, access to open and interoperable simulation tools will be important to ensure that the modeling approaches developed are available to researchers and companies across Europe. Supportive frameworks for intellectual property protection, commercialization of high-performance materials, and international cooperation in sustainable energy technologies will also enhance impact. In the long term, the predictive understanding achieved by TECTESA can inform standardization and regulation of new organic materials, ensuring both safety and environmental compliance.
In summary, TECTESA has moved the field beyond case-by-case descriptions toward a general and predictive understanding of exciton and charge transport in organic materials. The project’s scientific achievements strengthen Europe’s position at the forefront of theoretical materials research and lay the groundwork for the next generation of sustainable optoelectronic technologies.
Before the TECTESA project, theoretical studies of energy transport in organic materials were often based on simplified or static models that could not fully capture the complexity of real systems. These materials are composed of individual molecules interacting through weak forces, and their energy transport is governed by a delicate balance between electronic coupling, molecular vibrations, and structural disorder. Traditional models typically described only one of these aspects at a time, providing a fragmented and sometimes contradictory picture. As a result, researchers lacked general rules to predict how microscopic molecular arrangements determine macroscopic optical and transport properties.
TECTESA has advanced the state of the art by providing a unified theoretical understanding of how excitons—quasiparticles responsible for energy transfer—move through organic materials. By integrating atomistic-level information with semiclassical simulations, the project connected molecular packing, electronic structure, and dynamic fluctuations into a coherent framework capable of explaining and predicting exciton behavior under realistic conditions. This represents a significant conceptual step forward: instead of treating exciton motion as purely coherent (wave-like) or incoherent (hopping-like), TECTESA demonstrated that most organic materials operate in an intermediate, mixed regime where both mechanisms coexist. This insight reconciles previously inconsistent experimental observations and defines a continuum of transport behaviors determined by the relative strength of molecular coupling and vibronic interactions.
One of the key results of TECTESA was the identification of clear structure–property relationships that link molecular arrangement and electronic coupling to exciton delocalization and mobility. The project showed that specific packing motifs—such as slip-stacked or two-dimensional herringbone arrangements—promote partial delocalization, enabling energy to travel more efficiently through the material. Conversely, excessive disorder or strong vibronic coupling leads to localization, reducing transport efficiency. These findings allow researchers to predict, at a design stage, how a given molecular organization will perform, enabling more rational approaches to material synthesis and device engineering.
Another important contribution lies in the quantitative analysis of how molecular vibrations assist or hinder energy transfer. The project revealed that certain vibrational modes can dynamically enhance coupling between molecules, temporarily extending exciton coherence and improving mobility. This effect provides a physical explanation for the high diffusion lengths observed in some organic semiconductors and suggests that controlling vibrational dynamics—through molecular rigidity or chemical substitution—can be an effective strategy to optimize performance.
By establishing these general principles, TECTESA has provided the theoretical foundation for a predictive approach to organic material design. Its results are not limited to specific systems but can be extended to a wide range of soft and hybrid materials, including covalent organic frameworks (COFs), perovskite–organic composites, and molecular aggregates used in light-harvesting or sensing applications. The framework developed during the project can help identify the optimal balance between order and flexibility needed to maximize energy and charge transport, guiding both academic research and industrial innovation.
Potential Impact and Future Needs
The scientific insights from TECTESA have strong potential to influence how organic optoelectronic materials are designed and optimized. By providing clear design rules linking molecular packing to energy transport efficiency, the project can accelerate the discovery of materials for sustainable technologies such as organic photovoltaics, light-emitting diodes, and photodetectors. These applications directly contribute to the European Green Deal objectives of clean energy, circular materials, and reduced environmental impact.
To translate these scientific results into technological progress, several steps are needed. Further research should focus on integrating the theoretical insights into multiscale models that connect molecular behavior with full device performance. Collaboration with experimental and industrial partners will be essential to validate the predicted structure–property relationships and to identify synthetic strategies capable of achieving the optimal molecular arrangements identified by TECTESA.
For broader uptake, access to open and interoperable simulation tools will be important to ensure that the modeling approaches developed are available to researchers and companies across Europe. Supportive frameworks for intellectual property protection, commercialization of high-performance materials, and international cooperation in sustainable energy technologies will also enhance impact. In the long term, the predictive understanding achieved by TECTESA can inform standardization and regulation of new organic materials, ensuring both safety and environmental compliance.
In summary, TECTESA has moved the field beyond case-by-case descriptions toward a general and predictive understanding of exciton and charge transport in organic materials. The project’s scientific achievements strengthen Europe’s position at the forefront of theoretical materials research and lay the groundwork for the next generation of sustainable optoelectronic technologies.