The United States Air Force Research Laboratory (AFRL), headquartered at Wright-Patterson Air Force Base in Ohio (US), is using aerosol jet technology to more efficiently print perovskite solar cells directly onto arbitrary 3D structures. The new 3D-printing method could provide the needed universal platform for the lab-to-fab process transfer of solution-based perovskite photovoltaics and enable many new designs for embedded structural power applications.
To develop their manufacturing method, the research group atomized perovskite materials that can be 3D-printed with the aerosol jet machine. Coating a flat surface with droplets resulted in a device with 15.4% efficiency, showing that aerosol jet technology can enable scalable fabrication of high-quality printed thin-film perovskite, potentially ready to leave the lab soon.
The researchers then expanded the method by jet-printing the atomized perovskite directly onto three-dimensional surfaces. “Using direct-write aerosol jet technology, we further made 3D-printed perovskite solar cells directly onto a three-dimensional curved surface,” says project leader Santanu Bag, PhD, who nevertheless prefers not to discuss what vendor’s aerosol-jet technology they are using. Though the resulting solar cells were less efficient at 5.4%, the researcher does see potential for solar-powered 3D structures and projects such non-conventional methods for fabricating solar cells directly on the surface of arbitrary three-dimensional objects could enable many embedded structural power applications. “To date, a transfer process of fully manufactured solar panels has been primarily used to conform to non-planar form factors of three-dimensional objects,” he notes. “Our direct-printed 5.4%-efficient solar cell on a curved surface marks the first demonstration in the field of printed photovoltaics.”
Bag considers the application potentials “enormous” for the new printing process. “The method can be used to print flexible solar cells on clothing, to create self-powered robotics and light-emitting devices, and even to make flexible, self-powered sensors, to name a few.”
Advancing perovskite solar cells
“A high level of automation is desirable to facilitate the lab-to-fab process transfer of the emerging perovskite based solar technology,” the research scientist says. “To date, most demonstrations of this technology are limited to lab scale and based on an extremely labor intensive manual process in an inert atmosphere.”
He says a lot more research focused on the ‘lab-to-fab’ translation of the fabrication methods is required before the technology can evolve beyond the academic environment and become commercially viable at scale. “Unfortunately, the transfer of device results derived from a standard laboratory setup to fabrication level devices is non-trivial due to the enormous complexity of the thin-film perovskite growth dynamics and the lack of a generic protocol for fabricating high-quality, high-performing films that would ultimately lead to efficient solar cell devices,” he says. “Our autonomous approach could form a universal platform for the lab-to-fab process transfer of solution-based perovskite photovoltaics and steer development of new design strategies for numerous embedded structural power applications.”
Refining the process
“The major challenge of this project is the proper tuning of the materials crystallization process in order to get films with desired optoelectronic properties,” Bag says, reporting that without proper growth engineering, several types of defects are formed in the films. Large pinholes, impurities and small grains are a few examples he names. Nevertheless, with their own new materials crystallization growth technology they have developed, the AFRL team was able to overcome that barrier. “We had used a small mobile ion additive (e.g., sodium) in the ink to mitigate defects created during the process.”
The next step for Bag and his colleagues is to ramp up the speed of the process by “cleaner means,” he says. “Right now, the process is still slow and uses a layer-by-layer approach of depositing one component of the material at a time, and this makes the whole process quite lengthy.” He also notes that the inks they use contain hazardous solvents, which his team will be working on eliminating in the coming months.
Written by Sandra Henderson, Research Editor, Novus Light