The Emergence of Hybrid-Perovskites for Low-cost, High-efficiency Optoelectronic Devices

Abstract:
Hybrid (inorganic-organic) perovskites have demonstrated an extraordinary potential for clean sustainable energy technologies and low-cost optoelectronic devices such as solar cells; light emitting diodes, detectors, sensors, ionic conductors etc. In spite of the unprecedented progress in the past six years, one of the key challenges that exist in the field today is the large degree of processing dependent variability in the structural and physical properties. This has limited the access to the intrinsic properties of hybrid perovskites and led to to multiple interpretations of experimental data. In addition to this, the stability and reliability of devices has also been strongly affected and remains an open question, which might determine the fate of this remarkable material despite excellent properties. In this talk, I will describe our recently discovered approach for thin-film crystal growth as a general strategy for growing highly crystalline, bulk-like thin-films of both three-dimensional (3D) and layered two-dimensional (2D) hybrid perovskites that overcomes the above issues by allowing access to the intrinsic charge and energy transport processes within the perovskite thin-films and results in reproducible and stable high performance optoelectronic devices. Briefly, photovoltaic devices fabricated using 3D hybrid perovskites show hysteresis-free response, with high degree of reproducibility, with an average efficiency of planar devices approaching ~18%. Photo-physical, electrical characterization and theoretical modeling attribute the improved performance to reduced defects (bulk and interface) and improved charge-carrier mobility in large-grain devices. Furthermore, our most recent efforts on understanding and controlling photo-degradation in these systems demonstrate that the large grain-size perovskite thin-films are not limited by detrimental effects such as ion migration or defect assisted trapping generally reported for perovskite thin-film devices allowing us to probe true photo-physical processes that lead to the degradation of PCE in perovskite solar cells and control the light-induced degradation in these materials. Finally, I will also describe some new results on Ruddlesden-Popper phase perovskites based devices. In our first few attempts, we fabricated solar cells with efficiency approaching 13% as compared to the previous best of 4.5%. This phenomenal increase in efficiency is attributed to the near single-crystalline quality thin-films with a strongly preferential out-of-plane alignment of the inorganic perovskite component that facilitates efficient charge transport. Photovoltaic devices exhibit no hysteresis or degradation in performance under continuous operation and withstand an illumination intensity up to 4-Suns. Importantly, these devices with layered perovskites exhibit extraordinary, technologically relevant stability with no loss in performance with for ~2000 hours under humidity and 1-SUN full spectrum illumination.

Biography:
Aditya Mohite is the PI of the Light-to-Energy team and directs an energy and optoelectronic devices lab working on understanding and controlling charge and energy transfer processes occurring at interfaces created with organic and inorganic materials for thin-film clean energy technologies. His research philosophy is applying creative and “out-of-the-box” approaches to solve fundamental scientific bottlenecks and demonstrate technologically relevant performance in devices that is on par or exceeds the current state-of-the-art devices. He has published more than 80 peer reviewed papers in journals such as Science, Nature, Nature Materials, Nature Nanotechnology, Nano Letters, ACS Nano, Chemical Society Reviews, Applied Physics Letters and Advanced Materials amongst others. He has also delivered more than 50 invited talks.