8th Forum On New Materials
Plenary Lectures

F:PL1  Integrated Quantum Materials and Devices
R.M. WESTERVELT, Center for Integrated Quantum Materials, Harvard University, Cambridge, MA, USA

The Science & Technology Center for Integrated Quantum Materials joins faculty at Harvard University, Howard University, and MIT with public outreach through the Museum of Science, Boston. Our vision is to create quantum sensors, quantum communication networks and quantum computers based on new types of quantum materials. Quantum sensors exist now, quantum networks can be created in a few years, and quantum computers offer a long-term goal.  Our Center has four research areas: Novel van der Waals Heterostructures, led by Philip Kim, builds devices from atomic layer materials. Single layers of graphene, hexagonal boron nitride and transition-metal dichalcogenides conduct electricity well, even though they are only one atom or molecule thick. By stacking layers, one can couple metals, semi-metals, semiconductors and superconductors to create a wide variety of atomic-scale heterostructures for electronics and photonics.  Discovery of New Topological Crystals, led by Joseph Checkelsky, is creating new types of topological crystals. Topological insulators, discovered a dozen years ago, transmit information through edge states that circle their surface without an applied magnetic field.  Guided by theory, we aim to create topological crystals with a broader range of protection, through crystal growth and characterization.  Topologically Protected Qubits, led by Amir Yacoby and Pablo Jarillo-Herrero, aims to make topologically protected qubits for quantum computing that use topological insulators to guard against outside interference. Quantum Networks with Engineered Solid State Quantum Emitters, led by Marko Loncar, is creating quantum networks based on color center qubits in diamond.  A nitrogen vacancy (NV) center in diamond offers a qubit with coherence time > 1ms at room temperature and optical input/output coupling. Diamond photonics with optical resonators and strategically placed color center qubits are being created for quantum networks.
Supported by NSF grant DMR-1231319
Center website: http://ciqm.harvard.edu


F:PL2  Ultraflexible and Stretchable Electronics for Microvolt Biosignal Monitoring Systems
TSUYOSHI SEKITANI, The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, Japan

We review the recent progress in and future prospects of large-area, ultraflexible, and stretchable electronic sensors. Our work focuses on integration technologies for thin-film electronics comprising ultrasoft gel electrodes, thin-film amplifiers, Si-LSI platforms, thin-film batteries, and information engineering, which are imperceptible active sensors. Here, we discuss the applications of imperceptible sensors for patch-type biosignal monitoring sheets whose measurement accuracy is 0.2 µV. Further, wireless sheet-type electroencephalogram (EEG) and fetal electrocardiogram (ECG) monitoring systems for next-generation telemedicine that take full advantage of this flexible and stretchable electronic technology are detailed. These sheet-type sensors serve as important parts of seamless cyberspace/real-world interfaces that are commonly referred to as the Internet of Things and cyber-physical systems (IoT/CPSs). 
On the basis of our initial work on manufacturing ultraflexible and stretchable TFTs, we developed ultraflexible electronics for applications that use large-area sensors, actuators, memories, and displays. For example, by taking advantage of an ultraflexible and compliant thin-film amplifier that can amplify biological signals by a factor of 3000, we developed sheet-type multichannel EEG and fetal ECG monitoring systems. 
In addition to the abovementioned biomedical applications, we review a wide range of new applications, including the real-time health monitoring of civil infrastructures using all-printed large-area sensor systems.


F:PL3  Mesoscopic Photosystems for the Generation of Electricity and Fuels from Sunlight
M. GRAETZEL, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland

Photosystems using mesoscopic oxides as absorber materials or nanostructured scaffolds for transportation of photogenerated charge carrier have emerged as credible contenders to conventional p-n junction devices [1-3]. Mimicking light harvesting and charge carrier generation in natural photosynthesis, dye sensitized solar cells (DSCs) were the first to use three-dimensional nanaocrystalline junctions for solar electricity production, reaching currently a power conversion efficiency (PCE) of over 14% in standard air mass 1.5 sunlight. Remarkably the PCE increase to 29% in ambient light exceeding the performance of GaAs today’s best photovoltaic. By now, large-scale DSC production and commercial sales have been launched on the multi-megawatt scale for application in building integrated PV and light-weight flexible power sources. Recently, the DSC has engendered the meteoric rise of perovskite solar cells (PSCs) [4-7]. Today’s state of the art devices employ metal halide perovskite of the general composition ABX₃ as light harvesters, where A stands for methylammonium, formamidinium or caesium, B denotes lead or tin and X iodide or bromide. Carrier diffusion lengths in the 100 nm - micron range have been measured for solution-processed perovskites and certified power conversion efficiencies (PCEs) attain over 22.7 %, exceeding the PCE of the market leader polycrystalline silicon solar cells. These photovoltaics show intense electro-luminesence. and Voc values over 1.2 V for a 1.55 eV band gap material. This renders perovskite-based photosystem very attractive for applications in tandem cells and for the generation of fuels from sunlight mimicking natural photosynthesis [8,9]. 

1. B.O’Regan and M. Grätzel. “A Low Cost, High Efficiency Solar Cell based on the Sensitization of Colloidal Titanium Dioxide,” Nature 353 (1991) pp 7377-7381.
2. M. Grätzel, “Photoelectrochemical Cells,” Nature  414 (2001). pp  332-344.
3. A.Yella, H.-W. Lee, H. N. Tsao, C. Yi, A.Kumar Chandiran, Md.K. Nazeeruddin, EW-G .Diau,,C.-Y Yeh, S. M. Zakeeruddin and M. Grätzel, “Porphyrin-based Solar Cell with Co(II/III) Redox Electrolyte Exceed 12% Efficiency,“ Science 629 (2011) pp 334-341.
4. M. Grätzel, Light and Shade of Perovskite Solar Cells, Nature Mat. 13 (2014) pp 838-842.
5. J. Burschka, N. Pellet, S.-J. Moon, R.Humphry-Baker, P. Gao, M K. Nazeeruddin and M. Grätzel, "Sequential deposition as a route to high-performance perovskite-sensitized solar cells“ Nature 499, (2013), pp 316-3199.
6. X. Li, D. Bi, C. Yi, J.-D. Décoppet, J. Luo, S.M. Zakeeruddin, A. Hagfeldt, M. Grätzel, A vacuum flash–assisted solution process for high-efficiency large-area perovskite solar cells, Science 353 (2016), pp 58-62.
7. N. Arora, M.I. Dar, A.Hinderhofer, N. Pellet, F. Schreiber, S.M. Zakeeruddin, M. Grätzel, Perovskite solar cells with CuSCN hole extraction layers yield stabilized efficiencies greater than 20%. Science 2017, 358, 768-771.
8. J. Luo, J.-H. Im, M.T. Mayer, M. Schreier, Md.K. Nazeeruddin, N.-G. Park, S.D.Tilley, H.J. Fan, M. Grätzel, Water photolysis at 12.3% efficiency via perovskite photovoltaics and Earth abundant catalysts Science, 345, (2014), pp 1593-1596.
9. M.Schreier L. Curvat, F. Giordano, L. Steier, A. Abate, S.M. Zakeeruddin, J. Luo, M. Mayer and M:Grätzel, "Efficient photosynthesis of carbon monoxide from CO₂ using perovskite photovoltaics" Nature Commun. 6, (2015), pp 7326-7332.