« Back Paving the way for a solar future with Perovskite Photovoltaic Modules

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  • Solar energy without CO₂ emission is a powerful option for controlling abnormal weather caused by global warming.
  • The world’s most efficient perovskite solar cell, which is light, thin and flexible, can be applied in unprecedented locations such as cities and agriculture.
  • Perovskite solar cells contribute to a society where we can all enjoy a cleaner, safer and more sustainable future and a circular economy.

 

 

It is necessary to reduce greenhouse gas emissions in order to control abnormal weather caused by global warming. Solar power is the one of the most effective and important solutions of clean energy. Thin, light and flexible perovskite solar cells are a powerful option. Toshiba has developed the world’s most efficient large scale film-based perovskite solar cell and in doing so, will contribute to a society where we can all enjoy a cleaner, safer and more sustainable future. In this story, we’ll dig deeper into the details and significance of their technology.

 

 

Social problem we face; global warming and abnormal weather

Across the world, countries and organisations are striving to reduce their carbon emissions and meet ambitious sustainability goals. The recent United Nations Climate Change Summit (COP26) in Glasgow placed a magnifying glass on the current situation, and it is vitally important in the coming months and years that sustainability efforts continue to intensify both at a geopolitical, enterprise and societal level.

As carbon emissions are reduced, the emphasis must be placed on transitioning to renewable energy sources to replace them. Steady progress is being made here – according to the International Energy Agency (IEA), renewables made up 29% of global electricity generation in 2020. While hydropower is currently responsible for much of this, both wind and solar power are also growing in usage and expected to contribute to two-thirds of total growth in renewables. The concern is that, with over 70% of energy still being generated by non-renewable sources, the rate at which the transition to sustainable power generation is achieved needs to exponentially increase.

 

The rise of solar

Solar itself offers significant potential, but is one such renewable energy source yet to be maximised. There are several ways in which solar energy can be generated, including concentrated solar energy (CSP) and thermal, but currently photovoltaic (PV) modules are the primary source. Global electricity generation by this method is rapidly growing – it is expected to have increased by almost 18 per cent in 2021.

Yet even with this significant forward step, greater progress is required. As the IEA states, while “policy deadlines led to a PV deployment boom in 2020…more effort is needed to reach 2030 Net Zero levels.” Put simply, increasing usage of PV power generation will be essential to achieving carbon neutrality.

 

Maximising the potential of PV modules depending on the application

Today’s most widely used PV modules are made with crystalline silicon – a heavy and rigid composition which limits where they can be installed. For example, as of today mega-solar power plants have generally been installed on vacant sites or in mountains, but there are fewer places where conventional silicon mega-solar power plants can be installed. Yet given the need for more rapid acceleration towards solar, there is a growing need for large-scale electricity generation in urban areas. Local production for local consumption will be the key in the future.

Classification by material of solar cell

 

It is for this reason that the polymer film-based Perovskite PV module offers an attractive next-generation alternative, boasting a number of benefits over the widely-used crystalline silicon PV modules. Thinner, lighter and more flexible, Perovskite PV modules can be installed in locations where it is too difficult to use silicon PV modules, such as low load-bearing roofs and office windows. Within urban environments where space is at a premium, this offers a game-changing solution for solar power generation – significantly expanding the number of existing locations where PV modules can be installed. This also means we can fully utilize solar power of limited resource. One need only imagine the financial or business district of any major city, filled with glass-fronted buildings, to realise the opportunity for such technology.

While polymer film-based Perovskite PV modules have the potential to drive solar power generation to the levels needed to meet carbon net-zero targets, the current issue with them when compared to the silicon modules is their comparably inefficient power conversion efficiency (PCE) rates. That is to say, they cannot yet generate as much energy from a set amount of sunlight as their counterparts.

 

Innovation paving the way to change & widespread implementation

“Yet” is the crucial word in the previous sentence – the potential for Perovskite PV modules to deliver similar PCE rates to silicon versions is very much real, and Toshiba has made significant steps in achieving this through its innovative new one-step meniscus coating method. The coating method for Perovskite PV modules has been a stumbling block until now, as a previous two-step method led to a low-coating rate which often resulted in unreacted sections in the Perovskite layer – and subsequently a lower PCE.

The breakthrough one-step coating method boosts PCE to 15.1 per cent for a 703cm2 sized module – the world’s highest for any large, polymer film-based Perovskite photovoltaic module.*1 This is because Toshiba uses improved ink, as well as enhanced film drying processes and production equipment, to form a uniform Perovskite layer over the entire area. A further benefit is the speed at which the coating is applied, it now being 25 times faster than Toshiba’s previous two-step process. This results in the wider process being 50 times faster, given there is a need for just one layer of coating, and subsequently means the solution now achieves a rate that meets the requirements for mass production. In turn, this both simplifies and reduces the costs of production, making the technology a commercially viable option for the future.

*1: Based on a Toshiba survey of 100cm2 or larger film-based perovskite solar modules with a plastic substrate (As of 10th September, 2021)

“The characteristics of perovskite solar cells are determined by a wide range of conditions regarding materials and device structures. Therefore, I believe that all accumulation of knowledge from each development member contributes to improvement of characteristics.

In addition, I am very proud of the creativity and efforts by them who worked on the one-step method, which was thought to be much difficult, while it was common to form the film by the two-step method in a large-area perovskite solar cell.”

 

Isao Takasu
Fellow, Nano Materials and Frontier Research Laboratories Transducer Technology Laboratory, Corporate Research & Development Center, Toshiba Corporation

 

While these latest advancements are significant, there are further challenges ahead within the research and development phase before such technologies are ready to be commercialised, with Toshiba aiming to bring its modules to market in 2025. Within the next three years, there is a need to achieve even greater levels of conversion efficiency, as well as higher durability levels. It’s also important to bring down the manufacturing costs of the panels through the use of more cost-effective materials.

 

Applications from urban to rural environments

Coupled with the aforementioned benefits of Perovskite, Toshiba’s innovation paves the way for potential wide-scale implementation of next-generation solar panel technology. It’s estimated that the new technology could generate enough power to cover two-thirds of the annual power consumption by homes in Tokyo if installed on a roof area of 164.9km2 – roughly equal to the roof surface area of all buildings in Tokyo. Application examples aren’t just limited to metropolitan areas though, with the technology potentially beneficial across industries such as manufacturing and agriculture too.

 

 

Take the latter of these as an example. As you can control the transparency of Perovskite solar cells by how thin you make the layer of Perovskite, they can be used to cover greenhouses – enabling farmers to let in the correct amount of light as is required for the crops, while also generating the energy needed to power the farming process. When considering that agriculture was directly responsible for 8.5 per cent of all greenhouse gas emissions in 2019, according to the Intergovernmental Panel on Climate Change (IPCC), it’s clear that such technologies can have a major impact in helping some of the worst performing sectors work towards carbon net-neutrality and contribute towards a circular economy. The same applies to the buildings and building construction sectors, which, the IEA reports, combine to be “responsible for over one-third of global final energy consumption and nearly 40 per cent of total direct and indirect CO₂ emissions.”

 

A global effort towards net-zero

As society looks to navigate the numerous and varied environmental problems it now faces, including climate change and the depletion of energy resources, the role of solar energy alongside other renewables is of paramount important to building a sustainable future. Toshiba’s shares this vision, aiming to reduce greenhouse gas emissions by 70 per cent across its value chain by 2030, and closely aligning itself and its solutions to the UN’s Sustainable Development Goals (SDGs).

As a result, it’s commitment to developing innovative technologies such as polymer film-based Perovskite PV modules which help contribute to a circular economy is of paramount importance, and it will be interesting to see how the technology evolves in the future as more countries and organisations look towards a solar future. Aligned with this direction, Toshiba is now aiming to further improve the performance of perovskite PV modules. By gathering these much efforts, we may be able to expect society where we can all enjoy a cleaner, safer and more sustainable future and a circular economy.

The newly developed coating technology and the perovskite solar modules that apply it are research results under a New Energy and Industrial Technology Development Organization  (NEDO) project, Development of Technologies to Promote Photovoltaic Power Generation as a Main Power Source.

 

2022