Efficient Thin Film Solar Cells Inspired by Black Butterfly Wings

Innovation: Academia

CalTech & Karlsruhe Institute of Technology

2017

Image: Muhammad Yasir / Unsplash / CC BY SA - Creative Commons Attribution + ShareAlike

Transform Radiant Energy (Light)

The sun is the ultimate source of energy for many living systems. The sun emits radiant energy, which is carried by light and other electromagnetic radiation as streams of photons. When radiant energy reaches a living system, two events can happen. The radiant energy can convert to heat, or living systems can convert it to chemical energy. The latter conversion is not simple, but is a multi-step process starting when living systems such as algae, some bacteria, and plants capture photons. For example, a potato plant captures photons then converts the light energy into chemical energy through photosynthesis, storing the chemical energy underground as carbohydrates. The carbohydrates in turn feed other living systems.

Search this Function

Modify Light/Color

Color in living systems comes from pigments and the interaction of light with surfaces. Color serves many purposes for living systems, such as attracting prey or mates, providing warnings, or protecting through camouflage. To create the effects needed for each purpose, living systems must control the expression or visibility of pigments and the interactions (such as reflectance and refraction) of light. To do so, they have strategies that modify color or light to increase or decrease the color’s position, intensity, opacity, and more. Male hummingbirds, for example, have brightly colored feather patches on their throats; the coloring comes from pigments, structures that refract light, or a combination of the two. When a male hummingbird hovers near a potential mate, it modifies the angle of these feathers to create a bright, colorful display. However, when it needs to mute the colors to reduce conspicuousness, such as to avoid a predator, it modifies the angle again.

Search this Function

Thin film solar cells from CalTech and Karlsruhe Institute of Technology have disordered nanoholes that reduce light reflection.

Benefits

Efficient
Sustainable
Scalable

Applications

Commercial and industrial energy generation

UN Sustainable Development Goals Addressed

Goal 7: Affordable & Clean Energy

The Challenge

Thin film solar cells are lightweight and require less material to construct, making them a possible option for utility-scale solar projects. However, current thin film solar cells have high rates of light reflection, making them inefficient, as only absorbed light can be converted to energy.

Innovation Details

The high-efficiency thin film solar cells consist of hydrogenated, amorphous silicon sheets. The top layer has tiny holes of various sizes that cause light to scatter and strike the silicon base below. The base then absorbs the light to be used in solar energy generation. This design has proven to be roughly twice as efficient as typical thin film solar cells.

Biomimicry Story

Butterfly wings appear black not because of , but because they are able to absorb light with little to no reflection. This is made possible by a mesh-like surface of ridges and holes on the scales of the butterfly wing, which channels light into the scale’s interior. There, pillar-like beams of tissue scatter light until it is almost completely absorbed.

See Related Content

Biological Strategy

Butterflies Hack Light Waves to Produce Brilliant Color

Morpho butterfly

Wings of morpho butterflies create color by causing light waves to diffract and interfere.

References

Journal article

Bioinspired phase-separated disordered nanostructures for thin photovoltaic absorbers

Science Advances

embedly preview

AskNature