Photocapacitors for Ambient Energy Applications

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Intelligent wireless devices are rapidly evolving into indispensable assistants in numerous facets of our world. Merged with machine learning, wireless sensor networks are poised to advance the interchange of information in smart homes, offices, cities and factories. By 2030, an estimated 30 billion IoT (Internet of Things) devices are expected to be installed, the vast majority of which are to be placed indoors or in diffuse light conditions. IoT devices and wireless sensor nodes (WSN) will need to harvest energy from the environment for long-term deployment and operation. Indoor photovoltaic cells have the potential to provide the required energy. The power needed to operate these devices continues to decrease, while conversion efficiencies and hence the power output of indoor photovoltaic (IPV) cells is rapidly increasing. When located indoors with no access to solar irradiance, IPV cells harvest the energy emitted by artificial light sources, with the illumination intensity typically several orders of magnitude less than sunlight. Dye-sensitized IPV cells have shown considerable progress in terms of light to electricity conversion efficiency of late, with values over 30% measured under 200-1,000~lux light intensity. The collection of ambient light offers vast universally available energy, which can be used to design near-perpetual smart IoT devices. I have already developed the most efficient ambient light photovoltaic technology allowing one to implement artificial intelligence and image classification on self-powered IoT devices. In this proposal, I introduce a new design and energy paradigm to IoT devices, to maximize their ability to sense, communicate, and predict, powered by a dual-function device, an Energy-Storable Dye-sensitized Solar cell (ES-DSC). This device is a combination of energy harvester (Indoor Photovoltaic) and energy storage (a chemical supercapacitor). The chemical supercapacitor, a device that stores electrical energy in molecules, is based on organic redox materials, which are not only very efficient, but also sustainable and non-toxic. The intermittent character of the energy generation in IPVs will be bridged with the use of chemical supercapacitors to enable the overall IoT device to intermittently bridge periods of darkness for continuous operation. The proposed research focuses on innovating and implementing charge storing electrodes. I will focus on polyviologens, which have the ideal properties for IPV cells, are sustainable for electrical storage, and have not yet been applied in these emerging technologies. Funding from EPSRC will enable me to translate the favourable properties of polyviologens, firstly, by exploiting the high volumetric capacity of chemical supercapacitors to improve the performance, durability, and functionality of photovoltaic devices. Secondly, I will manipulate the backbone of the polymers to maximise the amount of charge that can be stored within the materials. Consequently, I will be able to fulfil my ambition of developing a new system that uses organic molecules, polyviologens, to integrate energy storage capabilities into solar cells to produce a single device capable of continuously powering electronic equipment during the day and at night. Success in this project will enable high efficiency light harvesting devices to be assembled at low-cost using roll-to-roll assembly, which would have enormous potential for societal and economic impact, including national and local jobs, supply chains, skills, and in reducing carbon emissions and fuel poverty.