Tandem solar cell technology promises to be the future of efficient and economical energy production. Tandem solar cells are optimized for a wider range of the sun's spectrum than traditional panels, and can generate more power from the same amount of space. Higher energy production per panel implies that you need less of most components of a solar generation system to generate the same amount of energy - less land area, fewer solar panels, and less labor and mounting systems to install them; this way, tandem solar panels can reduce energy generation costs across the board in many applications such as residential rooftops and utility scale solar farms. Higher efficiency tandem panels also make solar energy more practical for growing applications such as electric vehicles and satellites - thus, they can accelerate the production of renewable energy.
The Limitations of Traditional Solar Cells
The solar cells that you typically see on rooftops today are what are called “single junction” solar cells - where a single slab of material absorbs all the sunlight that shines on it. But as you can see in a rainbow, sunlight contains a variety of colors (or wavelengths of light), and a single material cannot be simultaneously optimized for all of the colors in sunlight’s spectrum: tailoring it to the blue light wastes some energy from the red end of the spectrum, but tailoring it to the red light wastes some energy on the blue end. This imposes a fundamental limit on how much of sunlight’s energy can be harvested by a single junction solar cell.
Tandem Solar Cells
Tandem solar cells are the most viable proven way to increase efficiency of solar cells beyond this limit. In a tandem solar cell, we stack one solar cell on top of another - to create multiple solar cells that work in tandem. The top cell can be optimized to absorb the blue end of the spectrum, while the longer wavelengths - the red end of the spectrum - go straight through the top cell and on to the bottom cell, which is optimized for these colors. This way, tandem solar cells are optimized for a wider range of the sun’s spectrum, which lets them achieve significantly higher efficiencies than traditional single-junction cells. This makes them promising candidates for the next generation of efficient solar panels.
Perovskite Materials for Efficient and Economical Solar Cells
A major scientific advance in solar energy research in the past decade is the advent of a new family of materials, known as metal halide perovskites, which have emerged as highly effective light absorbers in solar cells. A key advantage of perovskite materials is that they are highly tolerant to tiny defects that might form when they are made. Because of this tolerance to defects, they can be manufactured by fast and inexpensive methods and yet reach very high solar cell performance. This stands in contrast to other materials previously used to make efficient tandem solar cells - which need to be fabricated nearly perfectly in order to achieve their potential solar cell performance. This need for perfect fabrication has meant that they usually are slow and expensive to make. Because of this, tandem solar cells using more traditional materials have largely been limited to the most high-value of applications - such as high-budget satellites - where cost is not a dominant factor. With perovskites, however, we are able to use fast and inexpensive methods to make solar cells that are nonetheless highly efficient.
Unlocking the Future of Solar Energy
Perovskites also happen to be tunable, and we are able to tune them to absorb the right parts of the solar spectrum to be a perfect complement to existing silicon solar cells in a tandem solar cell. At Swift Solar, we make tandem solar cells with perovskite materials to create highly efficient solar cells that can be manufactured at scale and at reasonable cost. This promises to accelerate solar energy adoption by:
As research continues and manufacturing capabilities expand, perovskite tandem solar cells promise to play a crucial role in future energy systems. By making highly efficient solar power more accessible and affordable, we expect perovskite tandem cells to unlock the full potential of solar energy and accelerate our transition to affordable and sustainable power generation.
