Light fixes defects in perovskite solar cells

Light’s not only used by solar cells to produce electricity. It appears it can also sweep away minor defects.

Researchers from the US and UK, led by Dane deQuilletes from the University of Washington, claim tiny imperfections in perovskite solar cells can be “cleaned” with intense light.

While silicon is still king in the world of solar cells, there are other contenders. A promising family of minerals – perovskites – may one day lay claim to the throne.

Perovskites are fairly simple in terms of ingredients: usually lead, iodide and organic material. One type, organic-inorganic metal halide perovskites, is particularly efficient in solar cells. At the moment their production is too variable: various batches – even parts of the same organic-inorganic metal halide perovskite cell – can perform differently.

The secret to perovskites’ success is their neat crystalline structure. Electrons, bumped by incoming photons, trickle down through the crystalline perovskite to areas where their motion can be harnessed.

But if there are tiny defects in the perovskite, electrons are able to recombine with other atoms and their energy can’t be used. Efficiency, then, drops.

DeQuilletes and colleagues noticed when a blast of intense light is shone onto an organic-inorganic metal halide perovskite cell, its iodine ions – positively charged iodine atoms – behave strangely. They move away from the light – and, in doing so, clean up any defects in the perovskite crystal they encounter along the way.

Light’s cleaning effects tend to drop over time, co-author Samuel Stranks says, so “the challenge now is to maintain the effect” long enough to make it practical.

The work was published in Nature Communications.