Flexible multijunction solar cell looks to 45% efficiency
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Researchers in the UK have developed a multijunction solar cell technology that can be sprayed onto any surface with an efficiency of 27% and is aiming for 45%.
The team at Oxford University were able to print multiple thin layers of light-absorbing layers into one solar cell to capture more of the energy from the light. At just over one micron thick, it is almost 150 times thinner than a silicon wafer and can be applied to almost any surface. The multiple layers boost the conversion efficiency.
The cell has been independently certified to deliver over 27% energy efficiency, for the first time matching the performance of traditional, single-layer silicon solar cells by Japan’s National Institute of Advanced Industrial Science and Technology (AIST).
“During just five years experimenting with our stacking or multi-junction approach we have raised power conversion efficiency from around 6% to over 27%, close to the limits of what single-layer photovoltaics can achieve today,” said Dr Shuaifeng Hu, Post Doctoral Fellow at Oxford University Physics (above). “We believe that, over time, this approach could enable the photovoltaic devices to achieve far greater efficiencies, exceeding 45%.”
‘By using new materials which can be applied as a coating, we’ve shown we can replicate and out-perform silicon whilst also gaining flexibility. This is important because it promises more solar power without the need for so many silicon-based panels or specially-built solar farms,’ said Dr Junke Wang, Postdoc Fellow at Oxford University Physics.
He works on purely perovskite-based multijunction solar cells where the materials can be spray coated in multiple layers. The complex optical stack in a multijunction solar cell can lead to losses stemming from parasitic absorption and reflection of incident light which aggravates the current mismatch between sub-cells, thereby limiting the short-circuit current density of the tandem.
He previously developed an all-perovskite tandem solar cell that uses surface passivation strategies to reduce non-radiative recombination at the perovskite-fullerene interfaces, yielding a high open-circuit voltage. An optically benign transparent electrode and charge-transport layers boosted the performance to over 23%.
“We can envisage perovskite coatings being applied to broader types of surface to generate cheap solar power, such as the roof of cars and buildings and even the backs of mobile phones. If more solar energy can be generated in this way, we can foresee less need in the longer term to use silicon panels or build more and more solar farms,” said Wang.
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