Periodic Reporting for period 1 - HYTEM (Organic-inorganic hybrid thermoelectric materials through a new concept of simultaneous vapor phase coating and infiltration (VPI/SCIP))
Periodo di rendicontazione: 2021-11-08 al 2023-11-07
The goal of HYTEM was to develop advanced organic-inorganic hybrid thermoelectric materials by applying a concept of vapour phase infiltration (VPI) of polymers with inorganics. I developed thermoelectric materials with chemically linked organic/inorganic interfaces. The originality and a main result of this work lies in a newly developed materials set, where hierarchical superlattice structures of different inorganic materials are simultaneously grown in the subsurface of a polymer and on its top (as shown on the logo of the project), which allowed to obtain a superior thermoelectric performance. The success of HYTEM is of great importance for the EU as it created new options for the waste-to-energy industry. This goal was reached through following three specific objectives (SOs):
1. VPI-synthesis of Me nanoparticles inside the polymer bulk. (WP1)
2. VPI/SCIP synthesis of a hybrid TE. (WP2)
3. Characterization of the material and its TE properties. (WP3)
1. VPI-synthesis of Me nanoparticles inside the polymer bulk. (WP1)
2. VPI/SCIP synthesis of a hybrid TE. (WP2)
3. Characterization of the material and its TE properties. (WP3)
On the first stage of the project, I focused the work on monitoring the hybridization process in situ, using a Quartz Crystal Microbalance (QCM). QCM was integrated into the reactor dedicated for vapor phase infiltration of thermoelectric (TE) materials. The in situ monitoring allowed studying the saturation behaviour of the VPI process and quantitatively controlling the loading of inorganic precursors into a polymer. The combination of my experience in in situ QCM analysis of vapor-phase processes and the host´s expertise in polymer infiltration allowed investigations of infiltration. When the chemical and physical mechanistic behind these processes was understood, I moved to second stage of the project.
In the second stage of HYTEM, VPI was applied to the conducting polymers to grow hierarchical inorganic nanostructures and defect sites in the polymer bulk to increase the phonon scattering. I developed VPI of conductive polymers with n- and p-type semiconducting materials like Bi2S3, Sb2S3, Sb2Se3, Sb2Te3, Bi2Se3. Using VPI, I obtained a great control over the size distribution and gradient of the inorganic fraction and the overall composition of the designed hybrid materials.
In the third stage, during the secondment at Leibniz Institute for Solid State and Materials Research, I was doing full thermoelectric characterization of the obtained samples. Due to the better performance, later the work had been focused on p-type polymers and therefore on p-type inorganic materials respectively: Sb2S3, Sb2Se3, Sb2Te3. Sufficient TE activity at from room temperature considering their relatively small bandgap was achieved. The strategy of rational engineering of semiconductor interfaces allowed to enhance the ZT performance in TE materials with heterostructures.
Interesting results were obtained by doping p-type polymer PEDOT:PSS with n-type Bi2S3 to investigate how much we can impact on the nature of carriers and they mobility and whether we can measure that. As a result of the experiment- both, electrical and thermal conductivities decreased, that showed that the introduced n-type carriers compensated intrinsic p-type carriers, impacting carrier transport in PEDOT:PSS -Bi2S3 film. The measurement results for the Seebeck coefficient indicated transformation from p to n-type conductivity. That showed that we can impart properties, opposite to the intrinsic transport properties of the polymer using VPI infiltration with inorganic materials of different nature.
Unique results are obtained for PEDOT:PSS-Sb2Te3 hybrid film. The thermal conductivity of the film increased during first two temperature cycling stages, but within the third run when semiconducting behaviour transformed to metallic, thermal conductivity went down to a value of 0.3 W/mK. It could be that with the cooling, the degree of disorder increases by out of the plane orientated Sb2Te3 crystals formation, reducing thermal conductivity. For a typical material, when electrical conductivity is going up, thermal conductivity is also going up. Here I observed the unique case, that was the goal of my project- to decouple electrical from thermal conductivity. The maximum obtained ZT thermoelectric performance was 0.16 at 150 ˚C.
In the second stage of HYTEM, VPI was applied to the conducting polymers to grow hierarchical inorganic nanostructures and defect sites in the polymer bulk to increase the phonon scattering. I developed VPI of conductive polymers with n- and p-type semiconducting materials like Bi2S3, Sb2S3, Sb2Se3, Sb2Te3, Bi2Se3. Using VPI, I obtained a great control over the size distribution and gradient of the inorganic fraction and the overall composition of the designed hybrid materials.
In the third stage, during the secondment at Leibniz Institute for Solid State and Materials Research, I was doing full thermoelectric characterization of the obtained samples. Due to the better performance, later the work had been focused on p-type polymers and therefore on p-type inorganic materials respectively: Sb2S3, Sb2Se3, Sb2Te3. Sufficient TE activity at from room temperature considering their relatively small bandgap was achieved. The strategy of rational engineering of semiconductor interfaces allowed to enhance the ZT performance in TE materials with heterostructures.
Interesting results were obtained by doping p-type polymer PEDOT:PSS with n-type Bi2S3 to investigate how much we can impact on the nature of carriers and they mobility and whether we can measure that. As a result of the experiment- both, electrical and thermal conductivities decreased, that showed that the introduced n-type carriers compensated intrinsic p-type carriers, impacting carrier transport in PEDOT:PSS -Bi2S3 film. The measurement results for the Seebeck coefficient indicated transformation from p to n-type conductivity. That showed that we can impart properties, opposite to the intrinsic transport properties of the polymer using VPI infiltration with inorganic materials of different nature.
Unique results are obtained for PEDOT:PSS-Sb2Te3 hybrid film. The thermal conductivity of the film increased during first two temperature cycling stages, but within the third run when semiconducting behaviour transformed to metallic, thermal conductivity went down to a value of 0.3 W/mK. It could be that with the cooling, the degree of disorder increases by out of the plane orientated Sb2Te3 crystals formation, reducing thermal conductivity. For a typical material, when electrical conductivity is going up, thermal conductivity is also going up. Here I observed the unique case, that was the goal of my project- to decouple electrical from thermal conductivity. The maximum obtained ZT thermoelectric performance was 0.16 at 150 ˚C.
HYTEM presents an interdisciplinary and cross-thematic project, combining process technology, materials science, and energy conversion. Thus, many users stand to benefit from the research results.
With the rise of energy consumption and environmental pollution, the demand for clean and renewable energy sources and for minimizing the energy loss is of critical importance. Better energy efficiency can contribute to a better environment by reducing greenhouse gas emissions. Besides, there are economic impacts like reducing exploitation and transport of fossil fuels, which by themselves pose an environmental and economic issue. The EU made energy efficiency a pillar of its Energy Roadmap, which aims to reduce greenhouse gas emissions by 80-95% by 2050 (compared to 1990 levels).
One strategy towards improved efficiency involves capturing and recycling the “waste” heat from all energy conversion processes. A conversion of these heat losses into useful energy is an important energy source by itself.
The result of HYTEM – newly developed materials set: n- and p-type conductive polymers infiltrated with Bi2S3, Sb2S3, Sb2Se3, Sb2Te3, Bi2Se3, with a superior thermoelectric performance is of great importance for the EU, as it created new options for the waste-to-energy industry.
With the rise of energy consumption and environmental pollution, the demand for clean and renewable energy sources and for minimizing the energy loss is of critical importance. Better energy efficiency can contribute to a better environment by reducing greenhouse gas emissions. Besides, there are economic impacts like reducing exploitation and transport of fossil fuels, which by themselves pose an environmental and economic issue. The EU made energy efficiency a pillar of its Energy Roadmap, which aims to reduce greenhouse gas emissions by 80-95% by 2050 (compared to 1990 levels).
One strategy towards improved efficiency involves capturing and recycling the “waste” heat from all energy conversion processes. A conversion of these heat losses into useful energy is an important energy source by itself.
The result of HYTEM – newly developed materials set: n- and p-type conductive polymers infiltrated with Bi2S3, Sb2S3, Sb2Se3, Sb2Te3, Bi2Se3, with a superior thermoelectric performance is of great importance for the EU, as it created new options for the waste-to-energy industry.