These new semiconductors could revolutionize the solar energy industry
Halide perovskites
Our lab in Cambridge, England, is working with a promising new family of materials known ashalide perovskites. They are semiconductors, conducting charges when stimulated with light. Perovskite inks are deposited onto glass or plastic to make extremely thin films – around one-hundredth of the width of a human hair – made up of metal, halide, and organic ions. When sandwiched between electrode contacts, these films makesolar cells or LED devices.
Amazingly, the color of light they absorb or emit can be changed simply by tweaking their chemical structure. By changing the way we grow them, we can tailor them to be more suitable for absorbing light (for a solar panel) or emitting light (for an LED). This allows us to make different color solar cells and LEDs emitting light from the ultra-violet, right through to the visible and near-infrared.
Despite their cheap and versatile processing, these materials have been shown to be remarkably efficient as both solar cells and light emitters. Perovskite solar cells hit25.2% efficiency in 2019, hot on the heels of crystalline silicon cells at 26.7%, and perovskite LEDs are alreadyapproachingoff-the-shelf organic light-emitting diode (OLED) performances.
These technologies arerapidly being commercialized, particularly on the solar cell front. UK-based Oxford Photovoltaics hasbuilt a production lineand is filling its first purchase ordersin early 2021. Polish company Saule Technologies released prototype products at the end of 2018, including aperovskite solar façade pilot. Chinese manufacturer Microquanta Semiconductor expects to produce more than200,000 square metersof panels in its production line before year-end. The US-based Swift Solar (a company I co-founded) is pioneeringhigh-performancecells with lightweight, flexible properties.
Betweenthese and other companies, there is rapid progress being made.
Solar windows and flexible panels
Unlike conventional silicon cells, which need to be very uniform for high efficiency, perovskite films are comprised ofmosaic “grains”of highly variable size (from nanometers to millimeters) and chemistry – and yet they perform nearly as well as the best silicon cells today. What’s more, small blemishes ordefectsin perovskite films do not lead to significant power losses. Such defects would be catastrophic for a silicon panel or a commercial LED.
Although we are still trying to understand this, these materials are forcing the community to rewrite the textbook for what we consider as an ideal semiconductor: they can have very good optical and electronic properties in spite of – orperhaps even because of – disorder.
We could hypothetically use these materials to make “designer” colored solar cells that blend into buildings or houses, or solar windows that look like tinted glass yet generatepower.
But the real opportunity is to develop highly efficient cells beyond the efficiency of silicon cells. For example, we can layer two different colored perovskite films together in a“tandem” solar cell. Each layer would harvest different regions of the solar spectrum, increasing the overall efficiency of the cell.
Another example is what Oxford PV are pioneering: adding a perovskite layer on top of a standard silicon cell, boosting the efficiency of the existing technologywithout significant additional cost. These tandem layering approaches could quickly create aboost in the efficiencyof solar panels beyond 30%, which would reduce both the panel and system costs while also reducing theirenergy footprint.
These perovskite layers are also being developed to manufacture flexible solar panels that can be processed to roll like newsprint, furtherreducing costs. Lightweight, high-power solar also opens up possibilities for powering electric vehicles and communication satellites.
For LEDs, perovskites can achieve fantasticcolor qualitywhich could lead to advancedflexible display technologies. Perovskites could also give cheaper, higher qualitywhite lightingthan today’s commercial LEDs, with the “color temperature” of a globe able to be manufactured to give cool or warm white light or any desired shade in between. They are also generating excitement as building blocks forfuture quantum computers, as well asX-Ray detectorsfor extremely low dose medical and security imaging.
Although the first products are already emerging, there are still challenges. One key issue is demonstratinglong-term stability. But the research is promising, and once these are resolved, halide perovskites could truly propel the transformation of our energy production and consumption.
This article is republished fromThe ConversationbySam Stranks, Lecturer in Energy and Royal Society University Research Fellow,University of Cambridgeunder a Creative Commons license. Read theoriginal article.
Story byThe Conversation
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