Transparent organic photovoltaic glass façade

Prof Raymond Wong: metallopolymers for an energy efficient future

10 February 2018

Metallopolymers are interesting multifunctional materials with emerging applications in energy production and optical power limiting. Prof Raymond Wong explains.

Professor Raymond Wai-Yeung Wong (Croucher Senior Research Fellowship 2009, Fellowship 1996, Scholarship 1994 and Studentship 1992) is the Chair Professor of the Department of Applied Biology and Chemical Technology, and Associate Dean of the Faculty of Applied Science and Textiles at the Hong Kong Polytechnic University.

Known for his research in metallopolymers and metallo-organic molecules with photofunctional properties, Wong has spent decades advancing energy science with a specialism in developing technologies to promote efficient generation and consumption of energy.

Metallopolymers are metal-containing synthetic polymers which combine the processing advantages of polymers with the functionality provided by the presence of metal centres. Recent advances have found wide applications of metallopolymers in areas such as electrocatalysis, nanolithography, nano-electronics, and photonic crystal displays. Metallopolymers can also be used as optical power limiters; emitters in light-emitting devices, polymer precursors to magnetic metal alloy nanoparticles with potential to be utilised in fabricating magnetic data storage system, and as semiconductors in organometallic photovoltaic cells.

OLEDS and efficient energy consumption

Wong explains, “metal-based small molecules and polymeric compounds have a wide range of applications, especially in optoelectronics. One of our major interests is making Organic Light Emitting Devices (OLEDs); devices that are able to convert electrical energy into light energy.”

OLEDs have been hailed as the next generation of solid-state energy-saving lighting technology. They are currently being used in digital displays, from computer and laptop monitors to television and mobile phone screens. The development of white OLED devices; based on both polymeric and small-molecule organic materials, is the next phase of development. As well as being highly efficient, OLEDs provide ultra-thin large-area light sources, with high efficiency, colour-tunability, and colour-quality.

The conjugated functional organic chromophores are coupled with the phosphorescent properties of heavy transition metals to increase the phosphorescence emission efficiency, which in turn produces highly efficient light emitters, unlike purely organic molecules.

“Point of fact,” explains Wong, “OLEDs are energy saving devices. White OLEDs are a green technology with huge interest because as well as their high efficiency, they also consume much lower levels of power.”

Organic solar cells and energy generation

Wong also works within the field of photovoltaics, with a particular interest in organic solar cells. While OLEDs convert electrical energy into light energy, an organic solar cell is an organic photovoltaic device that uses carbon-based molecules, or polymers, to transform energy from sunlight into electrical power.

The main limitation of organic solar cells, historically, has been their efficiency (only 14% for single cells) and long-term reliability. Researchers and authorities worldwide have been focusing on the development of organic photovoltaics, intensively, for a number of years. Compared to conventional inorganic silicon-based solar cells; which are expensive and heavy, organic solar cells have low manufacturing costs, are flexible and light, and require lower energy to manufacture. Importantly, organic materials used in solar cells also allow researchers to tailor the molecular properties to fit the application.

“For our research purposes, we are making both efficient OLEDs and organic solar cells. While OLEDs reduce energy consumption and improve efficiency, organic solar cells work to generate renewable, efficient energy. Both of these are significant for the advancement of energy science,” explains Wong.

Other applications of metallopolymers

Wong expands, “Apart from the optoelectronic applications, we also continue to investigate other potential applications of metallopolymers. In particular, we have studied their optical power limiting applications.”

Laser beams emit light with high intensity which can cause damage to the human eye, as well as optical devices. The function of the optical limiter is to reduce the intensity of the original beam by transmitting low intensity light. A typical optical limiter consists of a nonlinear material, that is transparent at low light intensity. The optical limiter absorbs most of the high-level radiation, which can cause lasting damage.

The main idea of using metallopolymers is to develop optical limiters which are highly transparent, resulting in minimal absorption in the receptacle region, so that the material reduces the intensity of the laser beam, while allowing most of the colour from the original laser to pass through. This means that they are more suitable for making eye and optical device protectors.

Recently, metallopolymers have been used to make magnetic metal nanoparticles. The synthesis of iron-platinum alloy (FePt magnetic nanoparticles) has a high potential to be utilised in realising the ultra-high density magnetic data storage system.

Collaboration and challenges

Wong, who has spent decades trying to advance the field of metal complex chemistry, believes that collaboration between different disciplines is paramount, and he has worked closely with medical experts on applications within cancer research, and to develop several anti-bacterial agents, and light-emitting materials for bio-imaging studies.

Costly heavy transition metals, used by scientists in their research studies, continue to be a challenge in the field of synthetic chemistry. Wong argues that an alternative to these needs to be found; cheaper metals that are environmentally friendly in order to lower costs, maintain high performance, efficiency, and increase life span.

Despite the challenges of the field, Wong still devotes much of his time to carrying out research and mentoring his students. “I would like to help society develop methods that can solve the energy crisis, and at the same time, train talented early-career scientists to continue in this path.”

Professor Raymond Wai-Yeung Wong is currently the Chair Professor of Chemical Technology and Associate Dean of the Faculty of Applied Science and Textiles at the Hong Kong Polytechnic University. From 1998 to 2016, he served as the Chair Professor and Head of Department of Chemistry at the Hong Kong Baptist University.Wong obtained his B.Sc. (Hons) and Ph.D. from the University of Hong Kong, and did his postdoctoral research at the University of Cambridge, UK, and Texas A&M University, USA. With a distinguished career, Wong was the recipient of a Croucher Senior Research Fellowship Award in 2009. He received the Chemistry of the Transition Metals Award from the Royal Society of Chemistry in 2010. In 2012, he was awarded the Distinguished Lectureship Award from the Chemical Society of Japan, and was the recipient of the Japanese Photochemistry Association Lectureship Award for Asian and Oceanian Photochemistry, and the Second Class prize of the State Natural Science Award in 2013 and 2014. Wong was also listed as one of Thomson Reuters’ Highly Cited Researchers from 2014 to 2017.

To view Prof Wong's Croucher profile, please click here