Periodic Reporting for period 1 - OPVStability (Understanding, Predicting and Enhancing the Stability of Organic Photovoltaics)
Okres sprawozdawczy: 2023-09-01 do 2025-08-31
Photovoltaics is today a major pillar for a sustainable and clean electricity generation and contributes significantly to the reduction of carbon dioxide emission. The current technology is based on inorganic semiconductors, mainly crystalline silicon but also alternative thin film technologies. Organic photovoltaics (OPV) could possibly contribute to this, as OPV can be manufactured in efficient and low-cost roll-to-roll processes. OPV modules have reached power conversion efficiencies above 20%. However, in order to have a large impact, the long-term stability of OPV has to be improved.
OPVStability aims to develop an in-depth understanding of the degradation mechanisms and stability-promoting factors of organic photovoltaic materials and solar cells, to develop tools to predict the lifetime of devices and to identify stable structural motifs and device architectures as well as to develop strategies for efficient and stable OPV of the next generation.
OPVStability combines partners with a background in OPV and/or specialized scientific methods by combining theoretical calculations and simulations, experimental degradation studies on single materials, materials combinations and interfaces, accelerated aging and outdoor stability measurements, advanced analytics, high-throughput experiments and machine learning approaches. Within OPVStability, ten PhD-students work on this interdisciplinary research project accompanied with an excellent training program comprising scientific skills as well as a set of soft and transferable skills.
OPVStability aims to develop an in-depth understanding of the degradation mechanisms and stability-promoting factors of organic photovoltaic materials and solar cells, to develop tools to predict the lifetime of devices and to identify stable structural motifs and device architectures as well as to develop strategies for efficient and stable OPV of the next generation.
OPVStability combines partners with a background in OPV and/or specialized scientific methods by combining theoretical calculations and simulations, experimental degradation studies on single materials, materials combinations and interfaces, accelerated aging and outdoor stability measurements, advanced analytics, high-throughput experiments and machine learning approaches. Within OPVStability, ten PhD-students work on this interdisciplinary research project accompanied with an excellent training program comprising scientific skills as well as a set of soft and transferable skills.
WWithin the first reporting period, the main focus was set on the training activities. Besides these activities, each doctoral candidate has started with their individual research projects.
Work package 1: Stability of devices
The objective of WP 1 is an in-depth analysis of the ageing parameters on the lifetime of complete OPV devices including high-throughput screening, accelerated ageing tests and detailed device characterization. This allow a fast identification of suitable materials combinations and determination of the major degradation triggers. Materials and architectures are clustered according to their degradation trends, in order to select the most stable materials.
Activities were directed towards (accelerated) stability tests under controlled indoor as well as outdoor conditions with devices based on a set of high performing OPV materials, e.g. PM6/Y6, L8-BO/D18, and others. The initial test series already gave a first insight into the differences in stability of the materials, together with additional trends regarding the influence of film thickness and process parameters on the stability. These data are currently analyzed and will be used as input for further stability tests and input for the other scientific work packages.
Work package 2: Stability of materials, morphology and interfaces
WP2 focuses on the intrinsic stability of organic semiconductors and degradation pathways of materials, interfaces and absorber layer morphology. These are investigated by systematic studies at the nanoscale in order to understand degradation caused by the interactions of all components in a solar cell and to unveil hidden degradation triggers. This is combined with theoretical modelling and chemical space sampling to identify stable and weak structural components in OPV absorber materials.
Structural changes: Here, selected materials systems are studied under controlled ageing conditions, i.e. under dark conditions as well as under illumination in inert and ambient atmosphere. Changes in the absorption and emission spectrum give information on the bleaching of the conjugated system. These investigations are supported with resonant Raman spectroscopy showing structural changes of the chemical backbone.
Morphological changes: The nanophase morphology of the donor and acceptor in the active layer is of crucial importance for the efficiency. Thus, the thermal stability of the morphology was investigated using wide and small angle X-ray scattering methods on samples after different stages of thermal annealing.
Work package 3: Strategies toward next generation OPV
WP 3 is based on the results of the other WPs and will implement the findings in order to get highly efficient and stable solar cells. Additionally, the effect of antioxidants (e.g. additives known to inhibit degradation of organic (polymeric) materials) on the stability will be elaborated.
In this context, first test series with antioxidants have been carried out and yielded promising results.
Work package 4: Simulation, big-data analysis & machine learning
WP4 will implement big data mining, machine learning and simulations to analyze data generated via high throughput experiments in order to identify stable materials and to develop predictive models for next generation OPV devices.
Thus, work focused on the implementation of data management and processing guidelines, in order to make the project data usable. Furthermore, first machine learning models as well as simulation tools have been elaborated.
Work package 1: Stability of devices
The objective of WP 1 is an in-depth analysis of the ageing parameters on the lifetime of complete OPV devices including high-throughput screening, accelerated ageing tests and detailed device characterization. This allow a fast identification of suitable materials combinations and determination of the major degradation triggers. Materials and architectures are clustered according to their degradation trends, in order to select the most stable materials.
Activities were directed towards (accelerated) stability tests under controlled indoor as well as outdoor conditions with devices based on a set of high performing OPV materials, e.g. PM6/Y6, L8-BO/D18, and others. The initial test series already gave a first insight into the differences in stability of the materials, together with additional trends regarding the influence of film thickness and process parameters on the stability. These data are currently analyzed and will be used as input for further stability tests and input for the other scientific work packages.
Work package 2: Stability of materials, morphology and interfaces
WP2 focuses on the intrinsic stability of organic semiconductors and degradation pathways of materials, interfaces and absorber layer morphology. These are investigated by systematic studies at the nanoscale in order to understand degradation caused by the interactions of all components in a solar cell and to unveil hidden degradation triggers. This is combined with theoretical modelling and chemical space sampling to identify stable and weak structural components in OPV absorber materials.
Structural changes: Here, selected materials systems are studied under controlled ageing conditions, i.e. under dark conditions as well as under illumination in inert and ambient atmosphere. Changes in the absorption and emission spectrum give information on the bleaching of the conjugated system. These investigations are supported with resonant Raman spectroscopy showing structural changes of the chemical backbone.
Morphological changes: The nanophase morphology of the donor and acceptor in the active layer is of crucial importance for the efficiency. Thus, the thermal stability of the morphology was investigated using wide and small angle X-ray scattering methods on samples after different stages of thermal annealing.
Work package 3: Strategies toward next generation OPV
WP 3 is based on the results of the other WPs and will implement the findings in order to get highly efficient and stable solar cells. Additionally, the effect of antioxidants (e.g. additives known to inhibit degradation of organic (polymeric) materials) on the stability will be elaborated.
In this context, first test series with antioxidants have been carried out and yielded promising results.
Work package 4: Simulation, big-data analysis & machine learning
WP4 will implement big data mining, machine learning and simulations to analyze data generated via high throughput experiments in order to identify stable materials and to develop predictive models for next generation OPV devices.
Thus, work focused on the implementation of data management and processing guidelines, in order to make the project data usable. Furthermore, first machine learning models as well as simulation tools have been elaborated.
DC1 investigated the efficiency and stability of two new acceptor molecules and the results will be published soon. New insights into the thermal stability of high performance OPV materials was obtained.
The focus of DC2 is on a new strategy to investigate the triplet formation processes and their changes during ageing.
Antioxidants are a possible route to more stable organic solar cells, thus this strategy is researched by DC3. High throughput experiments were set up by DC4 focusing on a first study on low-cost and efficient photovoltaic modules for the use in urban environments. High quality outdoor stability data are produced by DC5 yielding key data for the project. The combination of absorption and emission properties with structural information of controlled-aged absorber layers are yielding valuable information to understand the structure-stability-relationship, as demonstrated by DC6.
New analytical tools for a detailed investigation of devices are topic of DC7. Thorough knowledge about changes of the morphology of the absorber layer (donor-acceptor phase separation), molecular packing and orientation due to different ageing conditions will be correlated to device stability by DC8. DC9 will use the large set of stability data from the project in combination with simulations and machine learning approaches. Finally, DC10 will elaborate on predictive models for the lifetime of OPV devices based on simple experimental data.
All these strategies and the combinations of this will yield to high impact publications and presentations and will enhance the knowledge of OPV beyond the state of the art.
The focus of DC2 is on a new strategy to investigate the triplet formation processes and their changes during ageing.
Antioxidants are a possible route to more stable organic solar cells, thus this strategy is researched by DC3. High throughput experiments were set up by DC4 focusing on a first study on low-cost and efficient photovoltaic modules for the use in urban environments. High quality outdoor stability data are produced by DC5 yielding key data for the project. The combination of absorption and emission properties with structural information of controlled-aged absorber layers are yielding valuable information to understand the structure-stability-relationship, as demonstrated by DC6.
New analytical tools for a detailed investigation of devices are topic of DC7. Thorough knowledge about changes of the morphology of the absorber layer (donor-acceptor phase separation), molecular packing and orientation due to different ageing conditions will be correlated to device stability by DC8. DC9 will use the large set of stability data from the project in combination with simulations and machine learning approaches. Finally, DC10 will elaborate on predictive models for the lifetime of OPV devices based on simple experimental data.
All these strategies and the combinations of this will yield to high impact publications and presentations and will enhance the knowledge of OPV beyond the state of the art.