The U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) has created an environmentally stable, high-efficiency perovskite solar cell, bringing the emerging technology a step closer to commercial deployment.
There are estimates that perovskite solar panels could cost just 10 to 20 cents per watt, compared to 75 cents per watt for traditional silicon-based panels — anywhere from 3X to 8X cost savings.
* The ingredients used to create perovskite are widely available and inexpensive to combine, since it can be done at relatively low temperatures (around 100ºC). Silicon cells need to be heated to high temperatures (as high as 900ºC) to remove defects, which is a costly process.
* Silicate perovskite may form up to 93% of the lower mantle, and the magnesium iron form is considered to be the most abundant mineral in Planet Earth, making up 38% of its volume.
* Versatility: Perovskite rolls have a thin, flexible and lightweight structure due to this processing, unlike silicon wafers, which tend to be thick, heavy and rigid. Because of this versatility, perovskite could theoretically be placed on roof shingles, windows or pretty much any surface imaginable. This versatility is what could enable solar to reach a scale that eventually eliminates dependence on fossil fuels entirely.
* Efficiency: As mentioned above, perovskite’s conversion efficiency has increased at an astounding rate over the last five years — from 4 percent to nearly 20 percent. And this is just the beginning — the theoretical limit of perovskite’s conversion efficiency is about 66 percent, compared to silicon’s theoretical limit of about 32 percent
Over the past decade, perovskites have rapidly evolved into a promising technology, now with the ability to convert about 23 percent of sunlight into electricity, but work is still needed to make the devices durable enough for long-term use. NREL’s unencapsulated solar cell—a cell used for testing that doesn’t have a protective barrier like glass between the cell’s conductive parts and the elements—held onto 94 percent of its starting efficiency after 1,000 hours of continuous use under ambient conditions.
Long-term device stability is the most pressing issue that impedes perovskite solar cell commercialization, given the achieved 22.7% efficiency. The perovskite absorber material itself has been heavily scrutinized for being prone to degradation by water, oxygen and ultraviolet light. To date, most reports characterize device stability in the absence of these extrinsic factors. Here we show that, even under the combined stresses of light (including ultraviolet light), oxygen and moisture, perovskite solar cells can retain 94% of peak efficiency despite 1,000 hours of continuous unencapsulated operation in ambient air conditions (relative humidity of 10–20%). Each interface and contact layer throughout the device stack plays an important role in the overall stability which, when appropriately modified, yields devices in which both the initial rapid decay (often termed burn-in) and the gradual slower decay are suppressed. This extensively modified device architecture and the understanding developed will lead towards durable long-term device performance.