Periodic Reporting for period 4 - p-TYPE (Transparent p-type semiconductors for efficient solar energy capture, conversion and storage.)
Berichtszeitraum: 2021-07-01 bis 2023-06-30
p-TYPE addressed scientific and technological challenges required to transform the use of solar energy by reducing payback time, improving manufacturability, innovating the technology for integration into buildings or devices and solving the energy storage issue. We developed tandem dye-sensitized solar cells, which were a unique way to make a step change in the efficiency of solar cells which function at a molecular level. An efficient tandem DSC has been challenging because p-type DSCs were much less efficient than n-type cells. The goal of this project was to increase the efficiency from < 2% to > 20% by replacing the nickel oxide conventionally used with a new material which was optimised for dye-sensitized photocathodes: a wide band gap to allow the dye to absorb the light; better conductivity for higher photocurrent; a higher ionisation potential for higher voltage. By adding catalysts to the device, we have driven chemical reactions such as carbon dioxide reduction or hydrogen production from water to make fuel, addressing the dual challenges of energy conversion and storage.
n-Type transparent conducting oxides were present in many devices, but their p-type counterparts were not largely commercialized as they exhibit much lower conductivities. The core part of the project focused on making libraries of mixed metal oxides and selecting those which were promising p-type semiconductors. We developed a high-throughput synthesis and screening system to accelerate the discovery and optimisation processes. Promising materials were assembled in tandem DSCs and tested. Our objectives were: A) Improve the efficiency of p-type dye sensitized solar cells and water-splitting cells by incorporating new p-type semiconductors which, for the first time, combine good transparency and high conductivity. B) Drive innovative engineering for the fabrication of high-efficiency low-cost tandem devices incorporating new photocathodes as a means of converting the majority of solar radiation striking the Earth. C) Underpin our research with state-of-the-art techniques for solar cell characterization to connect the fundamental research carried out at the molecular level and the events that take place in the device as a whole. p-TYPE’s findings could guide the optimisation of photoelectrochemical devices for sustainable energy generation and storage in the future.
n-Type transparent conducting oxides were present in many devices, but their p-type counterparts were not largely commercialized as they exhibit much lower conductivities. The core part of the project focused on making libraries of mixed metal oxides and selecting those which were promising p-type semiconductors. We developed a high-throughput synthesis and screening system to accelerate the discovery and optimisation processes. Promising materials were assembled in tandem DSCs and tested. Our objectives were: A) Improve the efficiency of p-type dye sensitized solar cells and water-splitting cells by incorporating new p-type semiconductors which, for the first time, combine good transparency and high conductivity. B) Drive innovative engineering for the fabrication of high-efficiency low-cost tandem devices incorporating new photocathodes as a means of converting the majority of solar radiation striking the Earth. C) Underpin our research with state-of-the-art techniques for solar cell characterization to connect the fundamental research carried out at the molecular level and the events that take place in the device as a whole. p-TYPE’s findings could guide the optimisation of photoelectrochemical devices for sustainable energy generation and storage in the future.
p-TYPE enabled us to develop two rapid and controlled routes to new semiconductor materials and morphologies to obtain libraries of compounds from which those with desired properties can be selected. We conducted a suite of experiments with these materials, including new screening protocols, to determine the structure property relationships which affect electron transfer and hole transport in p-type semiconductors. To make these experiments consistent, it was important that the synthesis routes enabled us to control, reliably and reproducibly, the different electronic and morphological properties of the materials in the library. We used a custom-made co-precipitation reactor where precursor salts were premixed before entering the reactor, where they were hydrolysed to form mixed metal hydroxides, which were collected and formulated into printable inks for applying in solar cells. For some classes of material and for depositing thin, uniform films on electrodes, this route was not always appropriate, so we built an automated ultrasonic spray system. Our third alternative was to automate successive ionic layer adsorption and reaction (SILAR), which can be used to grow or coat thin films of semiconductors This was mostly successful for light absorbing components, such as metal sulfides (Sustainable Energy and Fuels, 2019).
The ability to print metal oxide materials onto flexible substrates, particularly carbon cloth, stimulated the idea of developing wearable solar cells. This successful concept has captured the imagination of the public and Royal Air Force stakeholders. It inspired us to miniaturise our outdoor testing facility so that it could be worn (with the solar cells) by a person to evaluate the power that could be harvested to power a portable electronic device (e.g. for communication). Very few (if any) groups have been able to provide live data in this way that provides information for decision makes regarding how the technology could be developed and implemented. This has been showcased to the public at air shows including The Royal International Air Tattoo in 2022 and 2023 and the Miramar air show (San Diego) in 2022.
We have shown how combining molecules with metal oxide clusters or nanoparticles can be used to store charge so that it can be used to generate power in a solar cell or fuels from water, carbon dioxide and sunlight. Advanced spectroscopy allowed us to prove how careful control over the composition, structure and environment enabled us to accelerate the separation of charge and slow down charge recombination to improve the performance of devices. We have also been able to increase the performance of light-active electrodes that generate hydrogen or synthesis gas. This approach enables us to store the energy from sunlight over day-night or seasonal cycles and potentially could provide the feedstocks for fossil-free chemicals in the future.
We have presented results at several major national and international conferences including the American Chemical Society, Materials Research Society, Royal Society of Chemistry and Royal Society Meetings. We have also carried out public engagement activities to showcase our research at the Royal Society, Science Museum London and the Great North Museum (Hancock) Newcastle. We also worked on technology transfer and hosted an intern from an international company, who we trained to make flexible solar cells.
The ability to print metal oxide materials onto flexible substrates, particularly carbon cloth, stimulated the idea of developing wearable solar cells. This successful concept has captured the imagination of the public and Royal Air Force stakeholders. It inspired us to miniaturise our outdoor testing facility so that it could be worn (with the solar cells) by a person to evaluate the power that could be harvested to power a portable electronic device (e.g. for communication). Very few (if any) groups have been able to provide live data in this way that provides information for decision makes regarding how the technology could be developed and implemented. This has been showcased to the public at air shows including The Royal International Air Tattoo in 2022 and 2023 and the Miramar air show (San Diego) in 2022.
We have shown how combining molecules with metal oxide clusters or nanoparticles can be used to store charge so that it can be used to generate power in a solar cell or fuels from water, carbon dioxide and sunlight. Advanced spectroscopy allowed us to prove how careful control over the composition, structure and environment enabled us to accelerate the separation of charge and slow down charge recombination to improve the performance of devices. We have also been able to increase the performance of light-active electrodes that generate hydrogen or synthesis gas. This approach enables us to store the energy from sunlight over day-night or seasonal cycles and potentially could provide the feedstocks for fossil-free chemicals in the future.
We have presented results at several major national and international conferences including the American Chemical Society, Materials Research Society, Royal Society of Chemistry and Royal Society Meetings. We have also carried out public engagement activities to showcase our research at the Royal Society, Science Museum London and the Great North Museum (Hancock) Newcastle. We also worked on technology transfer and hosted an intern from an international company, who we trained to make flexible solar cells.
Our approach has enabled us to generate and test a large number of materials with different compositions, structures, morphology and doping. One of the most important outcomes was learning how to control the oxidation state of the metals, e.g. Cu+/Cu2+, while keeping the particle size small enough to make a conductive thin film with a high surface area for the light-absorbing pigments to attach to. Our research in tandem quantum-dot sensitized solar cells has advanced the efficiency beyond what has been achieved with dyes and has demonstrated the potential for flexible devices. We also learned how combinations of materials in layered structures can improve the performance beyond what can be attained with the individual materials. We learned through advanced spectroscopy how the interfaces between the light absorbing component and the p-type metal oxide differed from predictions made from bulk properties. This is key to the performance as the interface is where the most important charge-separation and recombination processes (which either help or hinder device performance) occur.
Towards the end of the project, we developed an outdoor testing facility to benchmark the device performance against different emerging solar cell technologies. Some preliminary results showed the advantages of emerging technologies in providing more power across day night and seasonal cycles due to the extra power generated at dawn and dusk. Finally, we learned how these properties and processes become even more important when developing solid state tandem solar cells, rather than the more traditional liquid-junction tandem dye-sensitized solar cells.
Towards the end of the project, we developed an outdoor testing facility to benchmark the device performance against different emerging solar cell technologies. Some preliminary results showed the advantages of emerging technologies in providing more power across day night and seasonal cycles due to the extra power generated at dawn and dusk. Finally, we learned how these properties and processes become even more important when developing solid state tandem solar cells, rather than the more traditional liquid-junction tandem dye-sensitized solar cells.