Solar cells are capable of efficiently harnessing energy from indoor light. Keyboards, remote controls, alarms, sensors, and all other devices could soon be battery-free.
Research team at University College London (UCL) has discovered a new generation of perovskite solar cells that has set a world record for indoor light conversion efficiency. The cells have achieved 37.6% at 1,000 lux, comparable to the brightness of a well-lit office. Tuned with a 1.75 eV bandgap for optimal indoor performance, the cells are expected to be around six times more efficient than the best currently available indoor solar cell alternatives. The cells are claimed to have an expected operational life exceeding five years.
As per experimental tests, the engineered cells maintained 92% of their initial efficiency even after 100 days, while unengineered control devices retained only 76%. The cells preserved 76% of their power output when subjected to 300 hours of continuous high-intensity illumination at 55°C, while other control samples dropped to just 47%.
Perovskite, the material which is used in the product development, is normally used in outdoor solar panels. The composition inside the cells is kept flexible so as to better absorb the specific wavelengths of indoor light.
The only key limitation, as per the research team, of perovskite lies in microscopic flaws in the form of tiny defects within its crystal lattice, called traps. Traps can capture electrons before they harness energy. This flaw hinders electrical flow and accelerates the material’s long-term deterioration.
However, researchers incorporated rubidium chloride, which promoted more uniform crystal growth with minimal internal strain, significantly lowering trap density. They also introduced two additional chemicals to stabilize iodide and bromide ions. This helped in preventing them from separating and clustering into different phases. These steps contributed in making perovskite indoor solar panels viable.
Lead author Siming Huang, said, “The solar cell with these tiny defects is like a cake cut into pieces. Through a combination of strategies, we have put this cake back together again, allowing the charge to pass through it more easily. The three ingredients we added had a synergistic effect, producing a combined effect greater than the sum of the parts.”
