Periodic Reporting for period 2 - HYTEC (Hybrid Organic Thermoelectrics: an Insight into Charge Transport Physics towards High-Performance Organic Thermoelctric Generators)
Période du rapport: 2019-07-01 au 2020-06-30
1. Importance for society
Thermoelectric generators (TEGs) are solid-state devices that directly convert heat to electricity. TEGs could be a valuable contributor to the world’s increasing demand for renewable energy, particularly when considering the amount of energy loss in terms of heat during our daily life. For instance, around 67% of the energy generated from hydrocarbon sources is lost as waste heat. In a silicon solar cell, approximately 50% of incident solar energy is lost by thermalisation and absorption. What is more, if we consider human body as a heat engine, it releases about 100W of thermal energy under basal metabolic condition, in which the energy loss is far sufficient to power most of microelectronic devices. In this case, TEGs provide a solution to tackle such a challenge of harvesting electrical energy from this significant amount of waste heat. One key advantage of TEGs is their scalability. TEGs are able to harness waste heat through various scales of sources: from something as big as industrial or geothermal sources, medium size such as home water heater, to even micro scale for instance microchips and human body. Thus, TEGs offer unlimited potential in various applications, such as co-generation, spacecraft, automotive, electronic skins, and Internet of Things (IoT).
2. Problem being addressed
Although demonstration of a bright future in wide applications, TEGs have long been too inefficient to be cost-effective in most applications. Fundamental to the thermoelectric field is the need to optimize a variety of conflicting properties of thermoelectric materials (TEMs). For TEMs, the efficiency of the heat-electricity conversion is dictated by a dimensionless figure of merit zT=P/κ, where P (P=α2×σ) is power factor and T is temperature. In order to fully implement the capacity of a TEG, its materials need to equip with high electrical conductivity (σ), large thermopower (α) and low thermal conductivity (κ). As these transport characteristics depend on interrelated material properties, a number of parameters such as carrier concentration, effective mass, and thermal conductivity, need to be optimized. Thermoelectrics require a rather unusual material: a ‘phonon-glass electron-crystal’. In order to achieve above behaviour, fundamental understanding of transport physics in TEMs is extremely important for both materials and process design. However, the transport processes has not yet been well understood since it is complicated by experimental evidence that clearly does not follow a single transport mechanism.
3. Overall objectives with Conclusions of the action
Three Objectives out of four were achieved:
Objective (i): to understand the charge transport of TEMs
Outcome: two models have been developed to understand the charge transport of TEMs, one has been published in Advanced Functional Materials ( https://doi.org/10.1002/adfm.201910079(s’ouvre dans une nouvelle fenêtre)). Another has been submitted and currently is under review in Nature Energy.
Objective (ii) to optimize their thermoelectric performance
Outcome: A grain boundary engineering approach has been developed to optimise the thermoelectric performance. The manuscript containing the relative results is under review in Nature Energy
Objective (iii) to fabricate the hybrid TEMs with optimised thermoelectric performance
Outcome: the fabricated TEM with maximum zT of 1.7 which meet original goal (zT>1.5). The manuscript containing the relative results is under review in Nature Energy
Objective (iv) to fabricate a prototype hybrid TEGs and demonstrate its application
Outcome: this objective has been severely disturbed by the Convid-19 pandemic. Both the labs in host organisation and the collaboration organisation were closed
Thermoelectric generators (TEGs) are solid-state devices that directly convert heat to electricity. TEGs could be a valuable contributor to the world’s increasing demand for renewable energy, particularly when considering the amount of energy loss in terms of heat during our daily life. For instance, around 67% of the energy generated from hydrocarbon sources is lost as waste heat. In a silicon solar cell, approximately 50% of incident solar energy is lost by thermalisation and absorption. What is more, if we consider human body as a heat engine, it releases about 100W of thermal energy under basal metabolic condition, in which the energy loss is far sufficient to power most of microelectronic devices. In this case, TEGs provide a solution to tackle such a challenge of harvesting electrical energy from this significant amount of waste heat. One key advantage of TEGs is their scalability. TEGs are able to harness waste heat through various scales of sources: from something as big as industrial or geothermal sources, medium size such as home water heater, to even micro scale for instance microchips and human body. Thus, TEGs offer unlimited potential in various applications, such as co-generation, spacecraft, automotive, electronic skins, and Internet of Things (IoT).
2. Problem being addressed
Although demonstration of a bright future in wide applications, TEGs have long been too inefficient to be cost-effective in most applications. Fundamental to the thermoelectric field is the need to optimize a variety of conflicting properties of thermoelectric materials (TEMs). For TEMs, the efficiency of the heat-electricity conversion is dictated by a dimensionless figure of merit zT=P/κ, where P (P=α2×σ) is power factor and T is temperature. In order to fully implement the capacity of a TEG, its materials need to equip with high electrical conductivity (σ), large thermopower (α) and low thermal conductivity (κ). As these transport characteristics depend on interrelated material properties, a number of parameters such as carrier concentration, effective mass, and thermal conductivity, need to be optimized. Thermoelectrics require a rather unusual material: a ‘phonon-glass electron-crystal’. In order to achieve above behaviour, fundamental understanding of transport physics in TEMs is extremely important for both materials and process design. However, the transport processes has not yet been well understood since it is complicated by experimental evidence that clearly does not follow a single transport mechanism.
3. Overall objectives with Conclusions of the action
Three Objectives out of four were achieved:
Objective (i): to understand the charge transport of TEMs
Outcome: two models have been developed to understand the charge transport of TEMs, one has been published in Advanced Functional Materials ( https://doi.org/10.1002/adfm.201910079(s’ouvre dans une nouvelle fenêtre)). Another has been submitted and currently is under review in Nature Energy.
Objective (ii) to optimize their thermoelectric performance
Outcome: A grain boundary engineering approach has been developed to optimise the thermoelectric performance. The manuscript containing the relative results is under review in Nature Energy
Objective (iii) to fabricate the hybrid TEMs with optimised thermoelectric performance
Outcome: the fabricated TEM with maximum zT of 1.7 which meet original goal (zT>1.5). The manuscript containing the relative results is under review in Nature Energy
Objective (iv) to fabricate a prototype hybrid TEGs and demonstrate its application
Outcome: this objective has been severely disturbed by the Convid-19 pandemic. Both the labs in host organisation and the collaboration organisation were closed
Overview of results
1. Understand in charge transport of the TEMs
a. All thermoelectric testing and modeling skills needed for the project were acquired.
b. Modeling work was done in several TEMs to simulate and predict thermoelectric performance of the thermoelectric systems based on acquired data
2. Develop nano-engineering approach to engineer TEMs
a. With fundamental understanding in charge transport through above modelling work, a specialised grain boundary engineering approach was developed to engineer TEMs
3. Optimise thermoelectric performance of a TEM
a. the grain boundary engineering approach was applied to engineer the TEM, of which the performance was optimised to a maximum of 1.7
Exploitation and dissemination.
1. Publications:
(i) Lin, Y. et al.; Graphene/Strontium Titanate: Approaching Single Crystal–Like Charge Transport in Polycrystalline Oxide Perovskite Nanocomposites through Grain Boundary Engineering, Adv. Funct. Mater. 2020, 30, 1910079. DOI:
10.1002/adfm.201910079
(ii)Lin, Y. et al.; Expression of Interfacial Seebeck Coefficient through Grain Boundary Engineering with Multi-Layer Graphene Nanoplatelets, Energy Environ. Sci. 2020, DOI: 10.1039/D0EE02490B
2. Conferences:
(i)Lin, Y. et al.; Energy Filtering Effect in Mg3Sb2 through Grain Boundary Engineering, North American Thermometric Workshop, Evanston, USA, (2019)
(ii)Lin, Y. et al.; Graphene/ Perovskite Oxides: Approaching Single-Crystal like Charge Transport in Polycrystalline Nanocomposites through Grain Boundary Engineering, The 38th International Conference on Thermoelectrics (ICT 2019), Gyeongju, Korea
(2019)
(iii)Lin, Y. et al.; Graphene Incorporation: An Effective Strategy to Enhance Performance of Thermoelectric Matrices, ICT2019
(iv)Lin, Y. et al.; Nano-Incorporation: An Effective Strategy to Enhance Performance of Thermoelectric Matrices, 2019 Nankai-Cambridge International Symposium on Advanced Materials, Tianjing, China (2019)
1. Understand in charge transport of the TEMs
a. All thermoelectric testing and modeling skills needed for the project were acquired.
b. Modeling work was done in several TEMs to simulate and predict thermoelectric performance of the thermoelectric systems based on acquired data
2. Develop nano-engineering approach to engineer TEMs
a. With fundamental understanding in charge transport through above modelling work, a specialised grain boundary engineering approach was developed to engineer TEMs
3. Optimise thermoelectric performance of a TEM
a. the grain boundary engineering approach was applied to engineer the TEM, of which the performance was optimised to a maximum of 1.7
Exploitation and dissemination.
1. Publications:
(i) Lin, Y. et al.; Graphene/Strontium Titanate: Approaching Single Crystal–Like Charge Transport in Polycrystalline Oxide Perovskite Nanocomposites through Grain Boundary Engineering, Adv. Funct. Mater. 2020, 30, 1910079. DOI:
10.1002/adfm.201910079
(ii)Lin, Y. et al.; Expression of Interfacial Seebeck Coefficient through Grain Boundary Engineering with Multi-Layer Graphene Nanoplatelets, Energy Environ. Sci. 2020, DOI: 10.1039/D0EE02490B
2. Conferences:
(i)Lin, Y. et al.; Energy Filtering Effect in Mg3Sb2 through Grain Boundary Engineering, North American Thermometric Workshop, Evanston, USA, (2019)
(ii)Lin, Y. et al.; Graphene/ Perovskite Oxides: Approaching Single-Crystal like Charge Transport in Polycrystalline Nanocomposites through Grain Boundary Engineering, The 38th International Conference on Thermoelectrics (ICT 2019), Gyeongju, Korea
(2019)
(iii)Lin, Y. et al.; Graphene Incorporation: An Effective Strategy to Enhance Performance of Thermoelectric Matrices, ICT2019
(iv)Lin, Y. et al.; Nano-Incorporation: An Effective Strategy to Enhance Performance of Thermoelectric Matrices, 2019 Nankai-Cambridge International Symposium on Advanced Materials, Tianjing, China (2019)
1. Results at the end of the project
With the success in analysis of SrTiO3 (Publication (i)Fig.1) I further analysed some other materials with grain boundary effects, such as PBTTT, P3HT, and Mg3Sb2. A generalized model for analyzing this category of TEMs with grain boundaries was established. A customized nano-engineering technique for each TEM studied was applied to optimize and enhance their thermoelectric performance(Fig.2). By the end of project, a TEM with optimised ZT≥1.5 was demonstrated (Publication (ii) Fig.3)
2. Impacts
Dissemination
Dr. Lin delivered 4 talks in 3 international conferences. One paper has been published in Advanced Functional Materials (impact factor 16.836) with another under review in Nature Energy (impact factor 46.495). One follow up project about development of advanced thermoelectric generator for room temperature applications has been proposed through Royal Society University fellowship scheme under collocation with European Thermodynamic Ltd., Nonwestern University USA, Manchester University UK, and NIMS Japan
The wider societal implications of the project so far
This project created immense social impacts both commercially and environmentally. By Dissemination in four international conferences, huge economic benefits were obtained through capturing massive public attentions with the introduction of efficient and sustainable energy harvesting materials. With support from the Cambridge Enterprise, the generated intelligence properties will be transferred to industry by activities such as licensing of patents. Thus, this project will also generate new markets in the production of TEMs and the exploitation of TEG modules for many energy companies such as European Thermodynamic Ltd.
With the success in analysis of SrTiO3 (Publication (i)Fig.1) I further analysed some other materials with grain boundary effects, such as PBTTT, P3HT, and Mg3Sb2. A generalized model for analyzing this category of TEMs with grain boundaries was established. A customized nano-engineering technique for each TEM studied was applied to optimize and enhance their thermoelectric performance(Fig.2). By the end of project, a TEM with optimised ZT≥1.5 was demonstrated (Publication (ii) Fig.3)
2. Impacts
Dissemination
Dr. Lin delivered 4 talks in 3 international conferences. One paper has been published in Advanced Functional Materials (impact factor 16.836) with another under review in Nature Energy (impact factor 46.495). One follow up project about development of advanced thermoelectric generator for room temperature applications has been proposed through Royal Society University fellowship scheme under collocation with European Thermodynamic Ltd., Nonwestern University USA, Manchester University UK, and NIMS Japan
The wider societal implications of the project so far
This project created immense social impacts both commercially and environmentally. By Dissemination in four international conferences, huge economic benefits were obtained through capturing massive public attentions with the introduction of efficient and sustainable energy harvesting materials. With support from the Cambridge Enterprise, the generated intelligence properties will be transferred to industry by activities such as licensing of patents. Thus, this project will also generate new markets in the production of TEMs and the exploitation of TEG modules for many energy companies such as European Thermodynamic Ltd.