Collaborative Research: Robotic Assembly of Multi-Dimensional Perovskite Thin Films for Breakthrough Light-Emitting Devices

As the Internet of Things and the emergence of smart materials proliferate, the demand for inexpensive, long-lasting, and efficient electroluminescent devices will continue to increase. Perovskites are solution-processible and Earth-abundant crystalline materials exhibiting high efficiency, attracting significant industrial attention. We have recently demonstrated simple light-emitting devices constructed from a single perovskite layer termed light-emitting electrochemical cells, which utilize battery-like charging to achieve high brightness and efficiency. Taking advantage of their simple architecture and facile construction, we will leverage robotic fabrication to rapidly produce arrays of varied perovskite thin film devices for optimized performance. To begin, we will precisely tune the lithium-ion charging of these devices for enhanced efficiency and stability. Next, we will robotically fabricate films and devices with a continuous range of colors, green through red, by tuning the chemical composition of the perovskite crystals. Finally, we will utilize robotic fabrication to tailor the crystal structures of these films, resulting in crystalline sheets that exhibit high-efficiency blue emission. This work will train undergraduate and graduate researchers for competitive careers in semiconductor technologies. The project will develop new technologies suitable for commercialization and provide insight into existing approaches. The program will create a new instrument for high-throughput device fabrication and testing. Finally, we will engage the public at large with an interactive color mixing and perception laboratory. A surge in the efficiency of perovskite light-emitting devices (PeLEDs) and light-emitting electrochemical cells (PeLECs) offers the potential for high-efficiency, low-cost, long-lived, and mechanically flexible light-emitting devices. Recently, we have demonstrated perovskite light-emitting electrochemical cells, devices that leverage differential ion motion to produce high performance in a simple, single-layer device. Through robotic fabrication of thin films and devices, we will achieve the following: -Robotic fabrication will enable fine-tuning of lithium doping concentration for optimized performance. Lithium doping has been shown to significantly improve the lifetime and performance of this class of devices. It is hypothesized that the lithium cation and counterions serve as surrogate mobile ions in these devices, replacing the parent ions of the perovskite. Additionally, these additive ions fill traps and passivate voids, thereby limiting nonradiative energy losses and stabilizing the perovskite crystallites. -Yellow to deep red electroluminescence will be achieved by robotically balancing the I− /Br− concentration ratio. Commercial LEDs have suffered from wide spectra with impure colors, particularly in the green-to-orange portion of the color gamut. Color tuning with a mixed iodine/bromine solution offers a pathway to address this, but the system is highly concentration dependent. Robotic assembly will enable consistently color-tuned and efficient devices for commercially underperforming LED colors. -3D-2D films will be robotically produced that incorporate small stacking number quasi-2D phases. The most promising perovskite devices, those with high efficiencies and world-leading lifetimes, have utilized multi-phase blends of perovskites. Two-dimensional phases blended with standard three-dimensional perovskite (3D-2D devices) are an emerging area for achieving breakthrough performance through quantum confinement in quasi-2D phases, utilizing spacer and coupling additives. This approach creates both an exciting opportunity and a significant challenge: Several 3D-2D fabrication methods are possible due to spacer and coupler molecules and their relative concentrations, but the throughput of traditional fabrication is highly rate-limiting. Robotic assembly will greatly boost the exploration of this exciting experimental landscape. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.