Ian Mathews

• Ph.D. Electrical and Electronic Engineering, B.Eng. Civil Engineering
• Fellow at Massachusetts Institute of Technology

Billions of everyday objects could become part of the Internet of Things (IoT) by augmentation with low-cost, long-range, maintenance-free wireless sensors. Radio Frequency Identification (RFID) is a low-cost wireless technology that could enable this vision, but it is constrained by short communication range and lack of sufficient energy available...

E-mobility, especially electric cars, has been scaling up rapidly because of technological advances in lithium-ion batteries (LIBs). However, LIBs degrade significantly with service life cycles. With the current increase in the adoption of electric vehicles (EVs), a large volume of retired LIB packs, which can no longer provide satisfactory perform...

The use of micro‐transfer printing presents a huge opportunity to decrease the cost of fabricating self‐powered sensors, by enabling heterogeneous integration of III‐V devices at the foundry wafer level. In article number 2000048, Brian Corbett and co‐workers demonstrate a GaAs laser power converter integrated on silicon, for power‐over‐fiber appli...

Here, the development of high‐efficiency microscale gallium arsenide (GaAs) laser power converters, and their successful transfer printing onto silicon substrates is reported, presenting a unique, high power, low‐cost, and integrated power supply solution for implantable electronics, autonomous systems, and Internet of Things (IoT) applications. 30...

The rapid proliferation of electric vehicles is creating a fleet of millions of lithium-ion batteries that will be deemed unsuitable for the transportation industry once they reach 80% of their original capacity. The repurposing and deployment of these batteries as stationary energy storage provides an opportunity to reduce the cost of solar-plus-s...

Here we report the development of high-efficiency microscale GaAs laser power converters, and their successful transfer printing onto silicon substrates, presenting a unique, high power, low-cost and integrated power supply solution for implantable electronics, autonomous systems and internet of things applications. We present 300 {\mu}m diameter s...

This paper investigates the suitability of CdTe photovoltaic cells to be used as power sources for wireless sensors located in buildings. We fabricate and test a CdTe photovoltaic cell with a transparent conducting oxide front contact that provides for high photocurrents and low series resistance at low light intensities - and measure the photovolt...

While the use of energy storage combined with grid-scale photovoltaic power plants continues to grow, given current lithium-ion battery prices, there remains uncertainty about the profitability of these solar-plus-storage projects. At the same time, the rapid proliferation of electric vehicles is creating a fleet of millions of lithium-ion batterie...

The significant capital expense of photovoltaics manufacturing has made it difficult for new cell and module technologies to enter the market. We present two technoeconomic models that analyze the sustainable growth of perovskite manufacturing for an R2R single-junction technology and a perovskite-silicon tandem module, focusing on the impacts of e...

High efficiencies of >30% are predicted for series-connected tandem solar cells when current-matching is achieved between the wide-bandgap top cell and silicon bottom cell. Sub-cells are typically optimized for current-matching based on the standard AM1.5G spectrum, but in practice, the incident radiation on a solar cell can be very different from...

A new approach to ubiquitous sensing for indoor applications is presented, using low‐cost indoor perovskite photovoltaic cells as external power sources for backscatter sensors. Wide‐bandgap perovskite photovoltaic cells for indoor light energy harvesting are presented with the 1.63 and 1.84 eV devices that demonstrate efficiencies of 21% and 18.5%...

Photovoltaic (PV) cells have the potential to serve as on-board power sources for low-power IoT devices. Here, we explore the use of perovskite solar cells to power Radio Frequency (RF) backscatter-based IoT devices with a few {\mu}W power demand. Perovskites are suitable for low-cost, high-performance, low-temperature processing, and flexible ligh...

Communication range in passive Radio-Frequency Identification (RFID) front-end devices is a critical barrier in the real-world implementation of this low-cost technology. Purely passive RFID tags power up by harvesting the limited RF energy transmitted by the interrogator, and communicate by backscattering the incident signal. This mode of communic...

We present a new approach to ubiquitous sensing for indoor applications, using high-efficiency and low-cost indoor perovksite photovoltaic cells as external power sources for backscatter sensors. We demonstrate wide-bandgap perovskite photovoltaic cells for indoor light energy harvesting with the 1.63eV and 1.84 eV devices demonstrate efficiencies...

Photovoltaic (PV) cells have the potential to serve as on-board power sources for low-power IoT devices. Here, we explore the use of perovskite solar cells to power Radio Frequency (RF) backscatter-based IoT devices with few µW power demand. Perovskites are suitable for low-cost, high-performance, lowtemperature processing, and flexible light energ...

Photovoltaic (PV) cells have the potential to serve as on-board power sources for low-power IoT devices. Here, we explore the use of perovskite solar cells to power Radio Frequency (RF) backscatter-based IoT devices with few \mu \text{W} power demand. Perovskites are suitable for low-cost, high-performance, low-temperature processing, and flexible...

The substantial capital expense of PV manufacturing has made it difficult for new technologies and companies to enter the market and compete on price with incumbents manufacturing modules at massive scale. We present a technoeconomic model that evaluates the start-up phase of a new PV manufacturing company by looking at the following question-how d...

Indoor photovoltaic cells have the potential to power the Internet of Things ecosystem, including distributed and remote sensors, actuators, and communications devices. As the power required to operate these devices continues to decrease, the type and number of nodes that can now be persistently powered by indoor photovoltaic cells are rapidly grow...

Communication range in passive Radio-Frequency Identification (RFID) front-end devices is a critical barrier in the real-world implementation of this low-cost technology. Purely passive RFID tags power up by harvesting the limited RF energy transmitted by the interrogator, and communicate by backscattering the incident signal. This mode of communic...

Indoor photovoltaic cells have the potential to power the Internet of Things ecosystem, including distributed and remote sensors, actuators, and communications devices. As the power required to operate these devices continues to decrease, the type and number of nodes that can now be persistently powered by indoor photovoltaic cells are rapidly grow...

Indoor photovoltaic cells have the potential to power the Internet of Things ecosystem, including distributed and remote sensors, actuators, and communications devices. As the power required to operate these devices continues to decrease, the type and number of nodes that can now be persistently powered by indoor photovoltaic cells is rapidly growi...

High efficiencies of >30% are predicted for series-connected tandem solar cells when current-matching is achieved between the wide-bandgap top cell and silicon bottom cell. Sub-cells are typically optimised for current-matching based on the standard AM1.5G spectrum, but in practice, the incident radiation on a solar cell can be very different from...

Integrated silicon photonics has emerged as a scalable optoelectronic platform to meet the demands for increased bandwidth in communication networks. However, integration introduces new thermal challenges to achieving the required system performance. Here we present the design of a micro thermoelectric temperature controller integrated around a III...

In the paper, we aim to solve the thermal problems appearing in integrated silicon photonics by using high thermal conductivity Aluminium Nitride (ALN) as a thermal spreading layer located around the ridge of a hybrid III–V laser on silicon in comparison to the existing encapsulation material benzocyclobutene (BCB). Here, to facilitate the design o...

Energy-harvesting systems provide power autonomy to individual wireless sensor nodes, allowing simpler deployment, as compared with wired nodes and longer lifetimes than battery-powered ones. Indoor light energy is an abundant source in many applications where solar cells are used to convert the radiant energy to electricity. To allow the greatest...

Integrated silicon photonics has emerged as a scalable solution to meet the demands for increased bandwidth in communication networks. However, integration introduces new thermal challenges for active photonic device performance. Traditionally, temperature sensitive devices have been isolated and cooled using centimeter-scale thermoelectric modules...

Mechanically stacked solar cells formed using adhesive bonding are proposed as a route to high-efficiency devices as they enable the combination of a wide range of materials and bandgaps. The concept involves adhesive bonding of subcells using polymeric materials widely used in semiconductor processing and outlines how the absolute efficiency can b...

Given the tight constraints on the wavelength stability of sources in optical networks, the thermal crosstalk between operating devices in a ten-channel thermally-tunable slotted laser array for DWDM applications has been investigated. It was found experimentally the current standard thermal solution with the laser array chip mounted on an AlN carr...

With the promise of highly integrated, high performance optoelectronic devices for communication applications, silicon photonics has emerged as a scalable solution to meet the demands for increased bandwidth in communication networks. An ultimate vision for silicon photonics realizes the integration of both electronic and photonic functionality in...

Aluminium Nitride (AlN) is proposed as a dual function optical cladding and thermal spreading layer for hybrid ridge lasers, replacing current benzocyclobutene (BCB) encapsulation. A high thermal conductivity material placed in intimate contact with the Multi-Quantum Well active region of the laser allows rapid heat removal at source but places a n...

GaAs solar cells are the highest efficiency single-junction photovoltaic technology. Their wide bandgap lends them to efficient conversion of indoor light. In this paper GaAs solar cells are experimentally compared to Dye Sensitised solar cells, traditionally used for indoor light harvesting. The power density of GaAs solar cells was found to be ov...

We present a low-cost fabrication process to deposit patterned inorganic nanoparticle films with submicrometer thickness and in turn to build higher dimensional structures through sequential multilayer deposition. Oxide nanoparticle films including semiconductors, dielectrics, and conductors have been patterned by moulding or imprinting from their...

Solar Energy is a clean and abundant energy source that can help reduce reliance on fossil fuels around which questions still persist about their contribution to climate and long-term availability. Monolithic triple-junction solar cells are currently the state of the art photovoltaic devices with champion cell efficiencies exceeding 40%, but their...

Thermal management has traditionally been relegated to the last step in the design process. However, with the exponential growth in data traffic leading to ever-greater levels of component integration and ever-higher levels of energy consumption, thermal management is rapidly becoming one of the most critical areas of research within the ICT indust...

A triple-junction cell based on a lattice constant of 5.816 Å using InAlAs -InGaAsP -InGaAs alloys can theoretically outperform those based on the GaAs lattice parameter by 3%. This lattice constant is close to that of InP but ultimately will require growth on a lower cost substrate such as GaAs or Si to have commercial impact. Here we present our...

The EU has set a target of 4% of all energy generated within the community to be generated by Photovoltaic (PV) solar energy by 2020 [1]. Global installations of PV solar energy increased by a factor of almost 15 from 2000 to 2011, helped largely by the development of large scale PV power plants, which now account for more than 50% of the world’s P...

Single junction In0.52Al0.48As solar cells have been grown on a (100) GaAs substrate by employing a 1 μm thick compositionally graded InxGa1−xAs/InP metamorphic buffer layer to accommodate the 3.9% mismatch. Cells processed from the 0.8 μm thick InAlAs layers had photovoltaic conversion efficiency of 5% with an open circuit voltage of 0.72 V, short...

A route to improving the overall efficiency of multi-junction solar cells employing conventional III-V and Si photovoltaic junctions is presented here. A simulation model was developed to consider the performance of several multi-junction solar cell structures in various multi-terminal configurations. For series connected, 2-terminal triple-junctio...

The power output of dual-junction mechanically stacked solar cells comprising different sub-cell materials in a terrestrial concentrating photovoltaic module has been evaluated. The ideal bandgap combination of both cells in a stack was found using EtaOpt. A combination of 1.4 eV and 0.7 eV has been found to produce the highest photovoltaic convers...

The power output of dual-junction mechanically stacked solar cells comprising different sub-cell materials in a terrestrial concentrating photovoltaic module has been evaluated. The ideal bandgap combination of both cells in a stack was found using EtaOpt. A combination of 1.4 eV and 0.7 eV has been found to produce the highest photovoltaic convers...

In response to the need for independent and personalised advice on sustainable design solutions from an easily accessible and centralised source, the Eco Design Advisor (EDA) scheme was initiated by BRANZ Ltd. The Eco Design Advisors are building experts working from the council and provide up to two hours of free eco-design advice on residential b...