“Imagine living or working in a building where nearly every exterior surface can generate renewable energy. Panasonic is pursuing this vision by developing next-generation solar panels based on perovskite, a material that makes solar power generation more practical in environments where conventional silicon has inherent limitations.
Perovskite is a term that has been used to refer both to a crystalline mineral and similar crystal structures in other materials. Gustav Rose, a German mineralogist who lived in the 19th century, found calcium titanate after prospecting in the Ural Mountains. He named its crystal structure “perovskite” after Lev Perovski, a Russian mineralogist and aristocrat.
What makes perovskite structures interesting in the battle against climate change is their ability to efficiently absorb sunlight and offer more sustainable manufacturing potential. In photovoltaic applications, perovskites consist of organic-inorganic hybrid materials with a perovskite structure.
The creation of the perovskite solar cell was important because perovskite solar panels can transcend the limits of silicon. Through thinner and more flexible designs, perovskites permit the expansion of solar power generation in ways that currently do not exist. When applied to the surface of other materials, for example, they can form a power generation layer.
While the use of solar panels has spread rapidly in recent years, accounting for nearly 10% of annual electricity production in Japan in 2021, conventional solar cells face a fundamental limit: most on the market can only capture about 20% of solar energy and convert it into electricity. This ratio has improved over the years, but the theoretical efficiency limit of silicon modules is 29%.
Since the invention of perovskite solar panels, the efficiency has climbed from 3.8% in 2009 to 25.2% in 2020. When used in tandem with silicon, small-scale perovskite cells have achieved efficiencies as high as 32.5%.
“Perovskite solar cells only began appearing in 2009, so it’s a young technology,” says Yukihiro Kaneko, General Manager at the Applied Materials Technology Center, Technology Division, Panasonic Holdings Corporation. “People have been working on small-scale cells to enhance efficiency but now we’re working on large-scale cells.”
At the 2023 Consumer Electronics Show (CES) in Las Vegas, Panasonic showed off 30-centimeter-square perovskite solar modules. Developed with Japan’s New Energy and Industrial Technology Development Organization (NEDO), they have the world’s highest efficiency for a perovskite module of its size, at 17.9%, according to an international ranking by the U.S. National Renewable Energy Laboratory.
The modules differ from conventional solar panels not only because they exclusively use perovskite as a photovoltaic material, and not silicon or silicon in combination with perovskite, but how they are made and can be used. The manufacture of conventional panels requires high heat, and lots of energy. This generates substantial amounts of greenhouse gases and means a relatively longer time for the panels to become carbon neutral.
Perovskite cells, on the other hand, do not require high heat treatment and can be produced with much less energy, making them cheaper and more sustainable. While it takes two to three years of power generation to recoup the energy used to make silicon cells, it only takes three or four months with perovskite cells, according to Kaneko.
Turning the windows and walls of buildings into power plants
Perovskite cells are also more versatile. The layer of perovskite crystals is less than 1 micrometer thick and is deposited on a glass substrate via inkjet printing. In addition to capturing sunlight on rooftops, they could generate power on the outer walls, balconies and other surfaces of homes and offices. They could even be used as windows. Panasonic has developed perovskite glass panels with 20%, 40% and graded transparency.
“Depending on the needs of the customer, we can change the transparency with laser and inkjet printing technology,” says Kaneko.
Thanks to the inkjet printing method, they are free from design limitations and are fully customizable. To demonstrate the design possibilities, at CES Panasonic exhibited a concept Perovskite Tree featuring nearly 1,000 “leaves” that were mockups of circular perovskite cells. This customizable quality could be a game-changing feature in a relatively small, mountainous country like Japan with very limited space for large solar farms.
Panasonic aims to commercialize perovskite panels in the next five years in order to realize Building Integrated Photovoltaics (BIPV), where ordinary architectural glass could be combined with perovskite cells to generate energy.
The concept dovetails with growing popularity of net zero-energy buildings (ZEB) and net zero-energy homes (ZEH). Such structures achieve net energy consumption of approximately zero through energy savings and onsite power generation with photovoltaics. By using normal glass, these panels could resolve reliability issues caused by the degrading effects of moisture on perovskite panels. In addition, architectural glass imparts long-term stability.
“Many people say that the problem of perovskite cells is reliability, but by using an impermeable glass substrate that shuts out moisture, we expect to achieve long-term reliability because structures cannot be rebuilt every 10 or 20 years,” Kaneko says.
The perovskite technology for BIPV is part of Panasonic GREEN IMPACT, an initiative to reduce emissions across the Panasonic value chain and achieve net zero CO2 emissions by 2030. A longer-term goal is to cut CO2 emissions by more than 300 million tons, or about 1% of global emissions of 33.6 billion tons, through group operations and by creating new technologies and businesses in hydrogen energy and other fields. These measures are also expected to help Japan achieve its commitment to become carbon neutral by 2050.
“We at Panasonic believe that the general picture going forward for perovskite solar technology is that it will be used on windows and walls,” says Kaneko. “This will be a great benefit to society through the avoided emissions of greenhouse gases that otherwise would be emitted.”
“Perovskite solar cells are an area where new markets will be created,” says Taisuke Matsui, a section manager of the 1st Division, Applied Materials Technology Center, Technology Division, Panasonic Holdings Corporation. “By integrating solar cells with building materials, they will become more closely connected to life than ever before. In this sense, it is important to continuously improve while reflecting the opinions of customers. We hope to learn about future technologies and receive various opinions that can be leveraged.””