Underwater Perovskite Solar Cells Could Generate Power Deep Below the Surface

In one episode of the Hanna-Barbera cartoon Birdman, the superhero struggles to fight the evil Dr. Shark aboard a submarine without solar energy to recharge his powers. Birdman might appreciate a new development from researchers at Yunnan University: perovskite solar cells designed to operate underwater.

Why use perovskite solar cells underwater?

Solar cells made from perovskites instead of silicon involve several important trade-offs. They are inexpensive to manufacture, can be produced in unusual forms such as thin, flexible, and transparent films, and can convert substantially more incoming solar energy into electricity. Their major weakness is durability: perovskite materials can deteriorate quickly.

Perovskites can be tuned for underwater light

Perovskites may seem like an unusual choice for underwater solar panels because moisture is particularly harmful to them. However, the materials have another key advantage: their light-absorbing properties can be tuned to target different wavelengths.

Water quickly blocks many of the wavelengths absorbed by conventional silicon solar panels. Carefully designed perovskite solar cells, however, can generate electricity from the deep blue light that remains available in ocean water. Lower light levels and cooler temperatures underwater could also help the cells last longer.

Protecting the cells from water damage

Tuning perovskites requires adjusting their chemistry during production, making it possible to create cells that absorb wavelengths found at depths of several meters. The greater challenge was making the cells durable enough for underwater use.

Led by Simin Ma at Yunnan University, the research team identified a particularly effective additive called polyhexamethylene guanidine hydrochloride. The additive helps create a water-repellent layer around the perovskite material. Some of its compounds also become part of the perovskite crystal lattice, encouraging the formation of larger crystals and preventing ions from moving through the structure.

By limiting several common pathways of perovskite degradation while improving power production, the additive could help make underwater perovskite solar cells more practical.