Publications de Hoi Nok Tsao | EPFL Graph Search

Optoelectronic and/or electrochemical learning device

The present invention concerns photoelectronic and/or optoelectronic learning device and/or memory device. In an embodiment, the device is a dye- sensitized solar cell. The short circuit photocurrent density (Jsc) of the device, and wherein a degree of a J ...

2018

A Stable Blue Photosensitizer for Color Palette of Dye-Sensitized Solar Cells Reaching 12.6% Efficiency

Shaik Mohammed Zakeeruddin, Hoi Nok Tsao, Yiming Cao

2018

Organic dyes containing fused acenes as building blocks: Optical, electrochemical and photovoltaic properties

Joël Teuscher, Hoi Nok Tsao, Peng Gao

2018

Illumination Time Dependent Learning in Dye Sensitized Solar Cells

Michael Graetzel, Hoi Nok Tsao

Learning through vision is an essential skill for intelligent machines. In an attempt to implement this highly complex feature at low energy cost, a dye-sensitized solar cell is proposed that learns using illumination time as a cue. Particularly, the devic ...

AMER CHEMICAL SOC2018

Enhancing the Stability of Porphyrin Dye-Sensitized Solar Cells by Manipulation of Electrolyte Additives

Michael Graetzel, Shaik Mohammed Zakeeruddin, Paul Joseph Dyson, Chenyi Yi, Hoi Nok Tsao, Pui Shan Genevieve Lau

The use of porphyrin-based photosensitizers with superior light-harvesting properties has enabled the power conversion efficiency of dye-sensitized solar cells (DSCs) to reach 13% under full sun illumination. However, a major limitation of such devices cor ...

Wiley-V C H Verlag Gmbh2015

Redox couple for electrochemical and optoelectronic devices

Michael Graetzel, Mohammad Khaja Nazeeruddin, Shaik Mohammed Zakeeruddin, Jun Ho Yum, Aswani Yella, Hoi Nok Tsao

The present invention provides an improved redox couple for electrochemical and optoelectronic devices. The redox couple is based on a complex of a first row transition metal, said complex containing at least one mono-, bi-, or tridentate ligand comprising ...

2014

Extended pi-Bridge in Organic Dye-Sensitized Solar Cells: the Longer, the Better?

Michael Graetzel, Mohammad Khaja Nazeeruddin, Chenyi Yi, Hoi Nok Tsao, Peng Gao

The elongation of pi-conjugated bridges between the donor (D) and the acceptor (A) represents a feasible strategy towards enhancement of light-harvesting in both breadth and depth of organic D-pi-A dyes suitable for nanocrystalline TiO2-based dye-sensitize ...

Wiley-VCH Verlag Berlin2014

Highly Stable Dye-Sensitized Solar Cells Based on Novel 1,2,3-Triazolium Ionic Liquids

Michael Graetzel, Shaik Mohammed Zakeeruddin, Paul Joseph Dyson, Hoi Nok Tsao, Pui Shan Genevieve Lau

We describe the design and synthesis of novel low viscosity bicyclic 1,2,3-triazolium ionic liquids. These new salts are applied as nonvolatile electrolytes in dye-sensitized solar cells, affording efficiencies up to 7.07% at low light intensities, and 6.0 ...

Amer Chemical Soc2014

Influence of Structural Variations in Push-Pull Zinc Porphyrins on Photovoltaic Performance of Dye-Sensitized Solar Cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, Chenyi Yi, Hoi Nok Tsao, Fabrizio Giordano

We designed and synthesized two new zinc porphyrin dyes for dye-sensitized solar cells (DSCs). Subtle molecular structural variation in the dyes significantly influenced the performance of the DSC devices. By utilizing these dyes in combination with a coba ...

Wiley-VCH Verlag Berlin2014

Dithieno[2,3-d;2 ',3 '-d ']benzo[1,2-b;4,5-b ']-dithiophene based organic sensitizers for dye-sensitized solar cells

Michael Graetzel, Mohammad Khaja Nazeeruddin, Hoi Nok Tsao, Peng Gao, Xin Guo

We report two novel D-pi-A type organic dyes with a coplanar dithieno[2,3-d; 2',3'-d']benzo[1,2 b;4,5-b']dithiophene (DTBDT) as pi-spacer for dye-sensitized solar cells. A best device performance with a power conversion efficiency of 6.32% is achieved, mak ...

RSC Publishing2014

Organic Sensitizers with Bridged Triphenylamine Donor Units for Efficient Dye-Sensitized Solar Cells

Michael Graetzel, Hoi Nok Tsao, Wei Zhang

Bridged triphenylamine was chosen as the donor unit for metal-free organic sensitizers in dye-sensitized solar cells (DSSCs). The easily constructed alkene linkage between the donor and the spacer improves the molecule's delocalization and causes a large r ...

Wiley-VCH Verlag Berlin2013

High Open-Circuit Voltages: Evidence for a Sensitizer-Induced TiO2 Conduction Band Shift in Ru(II)-Dye Sensitized Solar Cells

Michael Graetzel, Mohammad Khaja Nazeeruddin, Thomas Moehl, Hoi Nok Tsao, Kuan-Lin Wu, Filippo de Angelis

Dye-sensitized solar cells (DSC) represent a valuable, efficient, and low-cost alternative to conventional semiconductor photovoltaic devices. A deeper understanding of the interactions at the dye/semiconductor heterointerface is fundamental for future pro ...

American Chemical Society2013

Avoiding Diffusion Limitations in Cobalt(III/II)-Tris(2,2'-Bipyridine)-Based Dye-Sensitized Solar Cells by Tuning the Mesoporous TiO2 Film Properties

Pascal Comte, Michael Graetzel, Chenyi Yi, Hoi Nok Tsao

Dye-sensitized solar cells based on electrolytes containing cobalt complexes as redox shuttles typically suffer a major limitation in terms of slow diffusion of those couples through the mesoporous TiO2 film. This results in a drop of the photocurrent dens ...

Wiley-Blackwell2012

Fine-tuning the Electronic Structure of Organic Dyes for Dye-Sensitized Solar Cells

Michael Graetzel, Mohammad Khaja Nazeeruddin, Hoi Nok Tsao, Peng Gao

A series of metal-free organic dyes exploiting different combinations of (hetero)cyclic linkers (benzene, thiophene, and thiazole) and bridges (4H-cyclopenta[2,1-b:3,4-b']dithiophene (CPDT) and benzodithiophene (BDT)) as the central pi-spacers were synthes ...

American Chemical Society2012

Bistriphenylamine-based organic sensitizers with high molar extinction coefficients for dye-sensitized solar cells

Michael Graetzel, Mohammad Khaja Nazeeruddin, Hoi Nok Tsao, Filippo de Angelis

A series of novel bistriphenylamine-based organic sensitizers (coded as RC-dyes) with high molar extinction coefficients (>5.0 x 10(4) M-1 cm(-1)) have been synthesized for dye-sensitized solar cells (DSSCs). By changing the length of the pi-conjugation br ...

2012

Improved redox couple for electrochemical and optoelectronic devices

Michael Graetzel, Mohammad Khaja Nazeeruddin, Jun Ho Yum, Aswani Yella, Hoi Nok Tsao

The present invention provides an improved redox couple for electrochemical and optoelectronic devices. The redox couple is based on a complex of a first row transition metal, said complex containing at least one mono-, bi-, or tridentate ligand comprising ...

2012

Influence of the interfacial charge-transfer resistance at the counter electrode in dye-sensitized solar cells employing cobalt redox shuttles

Michael Graetzel, Mohammad Khaja Nazeeruddin, Julian Burschka, Chenyi Yi, Hoi Nok Tsao

We highlight the effect of the interfacial charge-transfer resistance at the counter electrode in dye-sensitized solar cells based on two cobalt redox shuttles, namely cobalt(III/II) tris(2,2'-bipyridine) and cobalt(III/II) tris(1,10-phenanthroline). Highl ...

2011

Porphyrin-Sensitized Solar Cells with Cobalt (II/III)-Based Redox Electrolyte Exceed 12 Percent Efficiency

Michael Graetzel, Mohammad Khaja Nazeeruddin, Shaik Mohammed Zakeeruddin, Aravind Kumar Chandiran, Aswani Yella, Chenyi Yi, Hoi Nok Tsao

The iodide/triiodide redox shuttle has limited the efficiencies accessible in dye-sensitized solar cells. Here, we report mesoscopic solar cells that incorporate a Co((II/III))tris(bipyridyl)-based redox electrolyte in conjunction with a custom synthesized ...

American Association for the Advancement of Science2011

Cyclopentadithiophene Bridged Donor-Acceptor Dyes Achieve High Power Conversion Efficiencies in Dye-Sensitized Solar Cells Based on the tris-Cobalt Bipyridine Redox Couple

Michael Graetzel, Mohammad Khaja Nazeeruddin, Shaik Mohammed Zakeeruddin, Jun Ho Yum, Thomas Moehl, Chenyi Yi, Hoi Nok Tsao

2011