New flexible solar cells made from non-toxic materials by a team at the University of NSW are sparking excited talk about 'zero-energy' buildings which generate as much power as they consume.
Until now, the promise of ‘zero-energy’ buildings been held back by two hurdles: the cost of the thin-film solar cells (used in façades, roofs and windows), and the fact they’re made from scarce, and highly toxic, materials.
The UNSW team, led by Dr Xiaojing Hao of the Australian Centre for Advanced Photovoltaics, is claiming the world’s highest efficiency rating for a full-sized thin-film solar cell using a competing thin-film technology, known as CZTS.
These cells are made from abundant materials: copper, zinc, tin and sulphur and recent test results in the US recorded a 7.6% efficiency in a 1cm square area cell.
Dr Hao said there is still some work to be done to catch up to its two thin-film rivals, CdTe (cadmium-telluride) and CIGS (copper-indium-gallium-selenide), both in terms of efficiency and cell size, but they are well on the way.
“This is the first step on CZTS’s road to beyond 20% efficiency, and marks a milestone in its journey from the lab to commercial product,” she said.
“I’m quietly confident we can overcome the technical challenges to further boosting the efficiency of CZTS cells, because there are a lot of tricks we’ve learned over the past 30 years in boosting CdTe and CIGS and even silicon cells, but which haven’t been applied to CZTS.”
Hao said thin-film technologies such as CdTe and CIGS are attractive because they are physically flexible, which increases the number of potential applications, such as curved surfaces, roofing membranes, or transparent and translucent structures like windows and skylights.
However, the toxicity of cadmium and selenium has made the construction industry – mindful of its history with asbestos – wary of using them. And the scarcity of elements like Tellurium and Indium also renders them unattractive, as price spikes are likely as demand rises.
Hao believes CZTS’s cheapness, benign environmental profile and abundant elements may be the trigger that finally brings architects and builders onboard to using thin-film solar panels more widely in buildings. The global market for so-called Building-Integrated Photovoltaics (BIPV) is already valued at US$1.6 billion.
Dr Xiaojing Hao with her CZTS solar cells. Photo: UNSW