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Translation by Claude:
Toyota’s ‘Rear Solar Panel’ that generates electricity from the headlights of the car behind
2026?3?22? 07:00
Summary> During a traffic jam at night, the solar panel on the rear bumper captures the headlights of the car behind and uses that energy to power the tail lamps. The key point is the use of perovskite solar cells, which match the wavelength of LEDs, as standard solar cells cannot capture LED light. A traffic jam, a situation where the following car keeps its lights on for a long time, is the ideal condition for this power generation method.
Publication of patent application: March 11, 2026
When stopped in a traffic jam at night, the headlights of the car behind reflected in the rearview mirror are nothing more than a nuisance. What if that light could be converted into electricity? This patent filed by Toyota proposes a mechanism where solar panels are attached to the rear bumper of a car to recover power from the headlights of following vehicles.
When it comes to vehicle-mounted solar panels, the standard is to place them on the roof or hood to generate power from sunlight. However, there is a limit to the available surface area. This patent focuses on the combination of an unused area—the ‘rear’ of the vehicle body—and ‘light sources other than sunlight’.
Why aren’t standard solar cells sufficient?
You might think that if you want to generate power from the headlights of the car behind, you could just attach standard silicon solar cells. However, it is not that simple. Each solar cell material has a ‘preferred light wavelength.’ Conventional crystalline silicon efficiently converts light in the near-infrared range (800–1050 nm) into electricity, but the energy of LEDs, which are the mainstream of modern headlights, is concentrated in the visible light range (350–700 nm). Because the wavelength bands are misaligned, silicon solar cells cannot effectively capture LED light.
This patent adopts perovskite solar cells. Perovskite is the name of a specific crystal structure, and solar cells made from materials with this structure excel in the 350–800 nm wavelength range. Since this almost overlaps with the emission band of LED headlights, light can be efficiently converted into electricity. The specification even analyzes the compatibility of different light sources, noting that crystalline silicon would be more advantageous if the following car is an older model with halogen lamps.
Uses for the generated electricity
Naturally, the amount of power generated does not compare to sunlight. With the light intensity from just one following car’s headlights during a traffic jam, one cannot expect enough power to charge the driving battery. Therefore, this patent limits the use of the generated electricity to ‘powering the tail lamps’.
The electricity generated by the rear bumper is supplied directly to the tail lamps or brake lamps located right next to it. Since it does not pass through the vehicle battery, the wiring is short and conversion loss is minimal. It is ‘local production for local consumption’ of energy. The specification also describes a control mechanism that monitors the power generation and, if it exceeds the power consumption of the tail lamps, supplies power directly from the solar panel, supplementing only the shortfall from the battery.
When keeping the brake lamps on during a traffic jam, that electricity is covered by the headlights of the car behind. The car in front receives the light and returns it to the car behind. Come to think of it, a traffic jam is an ideal condition for this power generation method, as the following car’s headlights continue to illuminate the rear of one’s own vehicle for a long time.
JP Patent Application 2026-042111 / Toyota Motor Corporation