By Katherine Mao
~ 9 minutes
Imagine a world where every surface—the walls, the roof of your car—harnesses the sun to power your surroundings. Not with stiff, bulky solar panels, but with something as simple and inconspicuous as paint.
Thanks to new and evolving technology, this vision inches closer and closer to reality. Perovskite-based photovoltaic paint is a developing technology with the potential to turn any paintable surface into a solar panel.
What are Perovskites?
Perovskites are a class of crystalline materials with the structural formula ABX₃. ABX₃ means that perovskites have a Large Cation(A), a Smaller Cation(B), and an Anion(X₃, often a halide). Their unique structure makes them incredibly efficient at converting sunlight into electricity, with recent developments reaching over 25% efficiency (25% of energy from the sun was converted into electricity), while traditional solar panels usually have 15-25% efficiency.
The Parts of Perovskite Solar Paint:
Perovskite-based solar paint must be applied in multiple layers. The six main layers, in order, are: the transparent conductive layer (front/top electrode), electron transport layer, perovskite absorber layer, hole transport layer, back electrode, and substrate.
The transparent conductive layer functions as the front electrode. It must be transparent, to allow sunlight to pass through, and conductive, to carry the extracted electrons.
Next is the electron transport layer, which extracts and transports electrons from the perovskite layer to the electrode and prevents holes from moving in the wrong direction.
The perovskite absorber layer is located at the center and is made of a perovskite compound that absorbs sunlight to create electron-hole pairs (excitons). It acts as the photoactive layer where sunlight is converted into electricity.
The hole transport layer lies below, which extracts and transports holes (the positive charges) to the back electrode and blocks electrons from going backward, aiding in charge separation.
The back electrode then collects the holes and completes the electrical circuit, allowing current to flow through an external device.
Finally, the substrate is the surface being painted (can be glass, plastic, metal, etc.) and provides structural support.
How Perovskite Solar Paint Works:
Sunlight first hits a perovskite layer, and the perovskite material absorbs photons. This excites electrons from the valence band to the conduction band, creating electron-hole pairs (excitons). In perovskites, excitons require little energy to separate into electrons and holes, which improves efficiency. Electrons are pushed toward the electron transport layer and holes toward the hole transport layer. The front and back electrodes collect the charges, and because oppositely-charged electrons and holes are separated and collected on different sides, a voltage builds up between the two electrodes. When the painted solar surface is connected to a circuit, the voltage drives electrons through the wire, powering a device or charging a battery.
A Game-Changer for Clean Energy
Perovskite-based photovoltaic paint could radically transform the solar energy industry. Unlike traditional silicon, which requires high temperatures and vacuum conditions for production, perovskite materials are cheap and efficient. Perovskite paint can also be applied to a wide variety of surfaces, allowing homeowners to harness solar power in places where solar panels are impossible.
The Challenges to Implementation
As promising as perovskite solar paint is, several significant challenges stand in the way of widespread implementation. Current perovskite materials are highly sensitive to moisture, heat, and UV light, meaning they degrade quickly outdoors. While silicon panels can last 25 years or more, early perovskite prototypes can lose efficiency after months or just weeks. Researchers are working on protective coatings and new formulations to address this, but achieving long-term durability remains a hurdle. Most high-efficiency perovskite formulas also contain lead or other toxic heavy metals, raising concerns about environmental contamination and safe handling.
Efforts to develop lead-free perovskites are ongoing (tin being a promising alternative), though they currently offer lower efficiency and a shorter lifespan. While perovskite solar paint and panels work well in laboratory settings, scaling up to commercial production is complex. A uniform coating that ensures proper perovskite crystallization must be applied over large areas, and surfaces must be treated to ensure adhesion and conductivity. In addition, regulatory bodies are still developing safety and performance standards for perovskite technologies. Gray areas remain about how these materials will be certified/recycled at the end of their lifespan.
Global Progress and Investment
In the U.S., the Department of Energy recently allocated over $40 million to perovskite R&D, focusing on improving durability and scaling up production methods. Startups like SolarPaint, Oxford PV, and Saule Technologies compete to bring the first market-ready products to consumers, while well-known companies like Mercedes-Benz seek to implement solar paint in their newest vehicles.
Conclusion
Perovskite-based photovoltaic paint is still in the early stages, but it represents one of the most exciting frontiers in renewable energy. If challenges like stability and toxicity can be solved, any painted surface could soon become a power source. Keep an eye on your walls—they might power the world someday.
Glossary
Valence Band:
- The highest range of electron energies where electrons are normally present at low energy (ground state)
- Valence electrons reside in the valence shell of atoms
- In any given material, atoms are packed closely together so their valence shells overlap and form the valence band
- Electrons here are bound to their atoms and don’t move freely.
Band Gap:
- The energy gap between the valence band and conduction band.
- Electrons must absorb enough energy (like from sunlight) to jump across this gap.
- The larger the gap, the more energy it takes to jump across, and the less conductive a material is
- Semiconductors like perovskites have a small gap(1-2 electron volts) and can conduct electricity if energy is added(sunlight)
Conduction Band:
- The higher energy band where electrons are free to move through the material.
- Electrons in this band can carry electricity.
Electron-hole pairs:
When a photon(light) hits the perovskite, it transfers energy to an electron, exciting it from the valence band to the conduction band.
- The excited electron in the conduction band moves freely and can conduct electricity.
- The “hole” is the spot the electron left behind—a positive charge in the valence band.
- There is now an electron-hole pair
Exciton:
- An exciton is the state where an electron and a hole are bound together, still attracted to each other by opposing charges
- Formed right after light absorption, before the electron fully separates from the hole/jumps to the conduction band.
- Neutral overall, so they don’t conduct electricity until they break apart.
- Common in some perovskites
Front and Back Electrode:
- They collect and transport electrical charges (electrons and holes) generated by sunlight.
- They’re like the “wires” of the solar paint that let electricity flow out into a usable circuit.
- Front electrode: Lets light in and collects electrons or holes(depends on design, usually electrons)
- Back electrode: Collects the opposite of what the front electrode does(back electrode usually collects holes) and helps drive current through an external circuit
Electron transport layer:
- Extracts and transports electrons to the correct electrode
Hole transport layer:
- Extracts and transports holes to the correct electrode
- The transport layers guide the charges(electrons(-) and holes(+)) to the correct electrodes, helping to prevent recombination (when electrons and holes meet and cancel each other out).
Voltage:
- Voltage is defined as the electric potential difference between two points.
- It tells you how much “push” electrons are getting.
- Measured in volts (V)
- Voltage is like water pressure in a pipe. The higher the pressure, the more push the water (electrons) is getting
Current:
- Definition: Current is the rate at which electric charge flows past a point.
- Measured in amperes (A), or amps
- More current = more electrons moving through the wire per second
- Current is like the amount of water flowing through the pipe. The wider or faster the flow, the higher the current.
Power:
- Definition: Power is the rate at which electrical energy is used or produced
- Measured in watts
- Formula: Power (P) = Voltage (V) × Current (I)
- Power is like how much water pressure × amount of water is turning a waterwheel—how much work is being done.
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