Hybrid and Organic Thermoelectric Systems

Project Information

HORATES

Grant agreement ID: 955837

DOI

10.3030/955837

Project closed

EC signature date 17 August 2020

Start date 1 March 2021

End date 28 February 2025

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 3 975 704,64

EU contribution

€ 3 975 704,64

Coordinated by

RUPRECHT-KARLS-UNIVERSITAET HEIDELBERG
Germany

Periodic Reporting for period 2 - HORATES (Hybrid and Organic Thermoelectric Systems)

Reporting period: 2023-03-01 to 2025-02-28

Summary of the context and overall objectives of the project

Waste heat is a source of low-quality energy waiting to be harnessed. Low-cost thermoelectric generators (TEG) based on organic materials and hybrid composites have the potential to transform this energy into electricity. The market for ultra-low power TEG is set to exceed 100 million USD, with a potential to reach billions as the Internet of Things (IoT) grows. Triggered by actual market demand for printable TEG, HORATES trains 15 promising early stage researchers (ESRs) in the emerging interdisciplinary field of organic thermoelectrics. ESRs are trained within a focused consortium that jointly cover the full chain from molecular design and synthesis via in-depth characterization and predictive multiscale modeling to large-area printed devices. HORATES integrates these scientific and technological aspects in a complete training package with complementary, transferable skills in order to equip young researchers with a unique toolset that is of relevance in both academia and industry, far beyond the specific topic of this project.

Overall objectives of the project
The ongoing development of the IoT leads to completely new opportunities for thermoelectric generators based on organic materials (OTEG), in which the eminent and unique strengths of organic (semi)conductors are exploited while their relative weaknesses are of less importance. These IoT applications include a wide range of society-relevant applications which would require power levels in the 10 µW range, while they need to be producible on large-scale, with low production costs, in different form factors, non-toxic and with a low price per unit. While all these specific requirements are difficult to fulfil with inorganic-based TEGs, (hybrid) organic materials offer the appropriate prerequisites here.
HORATES mission is to use the large expertise on all aspects of hybrid and organic thermoelectrics that is available in the European Union for (a) the training of excellent young researchers in an emerging, interdisciplinary field and (b) the development of prototype energy harvesters, inspired by actual market demand. To accomplish this mission HORATES reached its objectives as planned:
1) Synthesis of new, thermally and electrochemically stable organic materials and composites with record values significantly beyond the state-of-the-art.
2) Development of a general and basic understanding of the structure-morphology-property nexus.
3) Development of quantitative and predictive multiscale models for all quantities in zT.
4) Design and fabrication of stable printed OTEG modules with a power density p > 1 µW/cm2 at small temperature differences of 10°C.
5) Inclusive library of hybrid/organic printable TE materials as reference for future R&D activities.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Despite the pandemic situation at the beginning of the project, we have implemented all planned activities within the last two reporting periods. Starting with the recruitment of the ESRs and the establishment of a structure for coordination and continuous monitoring, through the development of targeted career plans and the implementation of the planned training activities, to the awarding of PhD degrees to the ESRs (in progress), we were able to achieve all the goals set in the area of management and training.
The planned scientific objectives have also been achieved. More specifically, this includes:
- Large scale synthesis of p- and n-type polymers with top zT values reaching zT > 0.5 (p-type), zT > 0.1 (n-type).
- Published open-access library of organic/hybrid TE materials with ~200 entries for p-type and ~120 entries for n-type materials.
Protocols for:
- ambient stability and solution aggregation of doped polymers as a base for ink formulation.
- degradation studies of materials and devices in a controlled and reproducible way.
- CNT/polymer nanocomposite fabrications.
- reporting of figures of merit (in progress).
Development of:
- methods to align polymers and determine the anisotropic TE properties.
- design rules for organic TE materials based on kinetic Monte Carlo simulations.
- models for the thermal conductivity and electronic properties of doped polymers and device design.
- Printed and textile TEG modules and a printed electronics control unit.
Overall, the HORATES consortium has thus achieved the ambitious goals set at the beginning of the project.
The research success of the last four years is reflected in 62 peer-reviewed publications to date, with more to follow in the coming months. All of this has been presented to the scientific community at numerous conferences and a symposium at E-MRS 2024, as well as to the general public via our website horates.eu a joint Twitter (now X) account and a yearly newsletter. The website also features webinars of recorded lectures on the HORATES topics and make them accessible to the public.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

HORATES has provided 15 promising young researchers with an interdisciplinary training that goes far beyond their specific topic within this project. The training was complemented with transferable skills relevant for a career in both industry and academia, enhancing the employability of the ESRs.
The work performed within HORATES generated scientific results that go beyond the state-of-the-art. Until the end of the project we developed printable organic/hybrid TE materials and inks with high zT’s which can be produced on the multigram scale. The experience gained in ink preparation and polymer processing led to (i) fully printed organic TEG with record normalized power densities, and (ii) large and robust textile generators with a power output that would be sufficient to power sensors based on OECTs.
The protocols and guidelines developed can help to establish a more structured, standardized and reproducible reporting of results and protocols in the field of organic thermoelectrics, as is already the case in other advanced fields of organic electronics. In addition, the database for organic and hybrid thermoelectric materials developed creates for the first time a data pool large enough to analyze thermoelectric parameters with some statistical relevance.
HORATES' close coupling of modelling and experimentation and integration of different scientific disciplines has made it possible to systematically address known problems within the field and, at the same time, to identify new avenues that can lead to a significant boost in thermoelectric power factor. As a consequence, the results obtained within the project can help a more targeted development of efficient organic and hybrid thermoelectric materials and devices, tailored to industrial requirements. With this, HORATES will contribute to the European Commission’s priority to transform the Union into a resource-efficient and competitive economy.

ESR Irene Brunetti measuring a flexible thermoelectic generator she fabricated within HORATES.