Tailoring Optoelectronic Processes in Metal Halide Perovskite via Piezoelectric and Piezo-Phototronic Effects

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Nontechnical:Metal halide perovskites represent an emerging class of materials for next-generation solar cells. The power conversion efficiency of perovskite solar cells has increased from 4% to 24% over the past ten years. These advances have come through controlling the crystallization of thin films, chemical modification, and interface engineering in devices. Although tandem devices with two different sub-cells could further improve efficiency, their manufacturing is complicated. This project uses a different strategy. The piezo-photonic effect couples mechanical stress, light absorption, and electricity. The project will use this effect to produce perovskite-based solar cells and photodetectors with markedly improved performance. Knowledge generated by this project will broadly impact applications of this class of interesting materials with applications in solar cells, photodetectors, and other electronic devices. This work will also strength nanoscience research. Summer research opportunities for high school teachers will provide a medium for transferring nanomaterials science and technology knowledge to high school classrooms. Underrepresented female undergraduate students will participate in the research and the experience of high school students will be enriched.Technical:This project aims to tailor the optoelectronic processes in the metal halide perovskite-based optoelectronic devices by capitalizing on the piezoelectric effect and piezo-phototronic effect. This will enhance the performance of metal halide perovskites, i.e., increased photocurrent and photovoltage in solar cells and improved sensitivity in photodetectors. (1) The crystal morphology and crystal orientation as well as electrical properties of perovskite thin films upon poling by an external electric field will be interrogated. (2) The effect of poling-induced changes in crystal morphology and crystal orientation via the application of an external electric field on the performance of perovskite solar cells and photodetectors will be explored. (3) The piezo-phototronic effect on the alternation of energy band under piezopotential at the perovskite/carrier transport layer interfaces enabled by the application of external strain will be scrutinized. The significance of this project lies in judicious exploration of piezoelectric effect on perovskite crystal morphology and crystal orientation as well as energy band alternation at perovskite/carrier transport layer interfaces to render the tailoring of photo-induced exciton dissociation, charge carrier transport, and charge carrier collection for high-performance piezo-phototronics-modulated perovskite-based devices. The resulting solar cells and photodetectors will exhibit greatly improved performance due to the piezo-phototronic coupling between polarization charges and photogenerated carriers, thereby transitioning fundamental scientific discoveries into useful technologies that benefit society.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.