| Work Detail |
An Austrian research team has tested lightweight, flexible and ultra-thin perovskite solar technology on palm-sized autonomous drones, highlighting the technologys stability and energy harvesting potential.
A team at Johannes Kepler University in Linz, Austria, has developed lead halide perovskite solar cells less than 2.5 µm thick with a champion specific photovoltaic power density of 44 W/g, and an average performance of 41 W/g, which they were able to integrate into modules to power palm-sized quadcopter drones.
The technology showed promising stability results in several standard tests, as well as sufficient energy harvesting potential to recharge the vehicles batteries. Details of his research appear in “ Flexible quasi-2D perovskite solar cells with high specific power and improved stability for energy-autonomous drones ,” published in Nature Energy.
The studys large-area photovoltaic module, measuring 24 cm2, enabled autonomous operation of the drone that extended “beyond what is possible with a single battery charge, while eliminating the need for docking, tethered charging or other forms of human intervention. The perovskite solar modules only represented 1/400 of the total weight of the drone.
The group tested various combinations of alpha-methylbenzyl-ammonium iodide (MBA) in the perovskite absorbent top layer, with PEDOT:PSS combining the electrode and hole transport functions. According to the researchers, the longer duration of the different MBA formulations included cesium (Cs), indicating “a reduction in non-radiative recombination pathways due to the presence of MBA and Cs.”
The substrate was a 1.4 µm thick “ultra-thin” transparent non-conductive oxide polymer sheet coated with a 100 nm aluminum oxide layer. It served as a “barrier” against humidity and gases.
“This type of device does not have room for typical encapsulation methods, which are too thick. Instead, the team relied on the formation of large, bulky crystals from the top layer of MBA perovskite to effectively passivate the surface, and for the substrate, the aluminum oxide layer applied with the atomic layer deposition tool ( ALD) serves to protect from external conditions, but while remaining light and flexible,” the research leader, Martin Kaltenbrunner, explained to pv magazine .
In fact, the article notes, for example, that the water vapor transmission rate (WVTR) of the “coated ultrathin substrate was measured to be 35% lower” compared to the reference designs, which were methylammonium iodide devices. and lead (MAPbI3).
Other features of the perovskite cell are an electron transport layer made of phenyl-C61-butyric acid methyl ester (PCBM) with a middle layer of titanium oxide, and a top metal contact, which the group noted could be made either of gold, or chrome/gold, or low-cost aluminum.
“In our research on solar perovskite it is important to use precursors that are synthesized in as few steps as possible. A simple synthesis is key because we want the technology to be scalable and keep material production costs under control,” says Kaltenbrunner.
From cell to module
The small area perovskite solar cell in the study measured 0.1 cm2 with an open circuit of 1.13 V, a short circuit current density of 21.6 mA cm-2, a fill factor of 74.3%, and a power conversion efficiency of 18.1%. The champion cells achieved an open circuit voltage of 1.15 V, a fill factor of 78% and an efficiency of 20.1%.
The largest device had an active area of ??1.0 cm2, with an average open circuit voltage of 1.11 V, a short circuit density of 20.0 mA cm-2, a fill factor of 65.9%, and an efficiency of 14.7%. The champion device achieved an efficiency of 16.3%, the research team stated.
The module to power the drone had 24 interconnected 1 cm2 solar cells. The commercially available autonomous quadcopter-type solar-powered hybrid drone weighed only 13g.
Stability and long-term operability outdoors were tested. For example, small- and large-area unencapsulated solar cells maintained 90% and 74% of their initial performance, respectively, after 50 h of continuous maximum power point tracking (MPPT) in ambient air. Additionally, an external laboratory validated the performance and properties of the perovskite composition.
The team claims that it has demonstrated the “broader advantages of using a quasi-2D perovskite active layer” and that it outperforms “other compositions in this field,” adding that the performance, stability and ease of use of the solar technology ultralight perovskite is a “portable and cost-effective sustainable energy harvesting solution.”
As a drone charging system, it represents a step forward on the path towards the “development of perpetual operating vehicles”, both for aerospace and terrestrial applications.
The team has plans to continue researching along these lines. “We will continue working to develop AlOx barrier substrate technology, scalable deposition techniques, and to scale to even larger modules, measuring at least 10cm X 10cm. Our goal is to develop lightweight and flexible photovoltaic solutions to power all types of robotics and autonomous vehicles,” says Kaltenbrunner. “There is great potential for deployable and flexible solar PV in both terrestrial and space applications.” |
