Nanoscale and Bulk Perovskite Single-Crystals: Surface Engineering for Efficient LEDs, Photodetectors, and Solar Cells
Osman M. Bakr a
a Materials Science and Engineering, King Abdullah University of Science and Technology (KAUST), Saudi Arabia
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)
Roma, Italy, 2019 May 12th - 15th
Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo
Invited Speaker, Osman M. Bakr, presentation 045
Publication date: 11th February 2019

In colloidal nanocrystal form, lead halide perovskites possess high photoluminescence quantum yields, while in bulk single-crystal form they exhibit long charge-carrier diffusion lengths. However, without proper strategies to diminish crystal surface defects and manage surface quality, the desired characteristics of perovskites cannot be effectively exploited for photovoltaic and optoelectronic devices. Here I discuss novel strategies to passivate the surface defects and improve the surface quality of perovskite nanocrystals and bulk single-crystals, enabling the fabrication of efficient devices. We demonstrate the passivation of CsPbX3-type nanocrystals with molecular ligands and metal dopants leading to stable near-unity quantum yield emitters, as well as efficient blue and red light-emitting diodes (LEDs). We also show the importance of designing crystal growth conditions, such as solvent, temperature, and substrate in order to grow bulk single-crystals with low-defect densities and good surface quality. Depending on the composition, MAPbX3-type single crystals grown (tens of microns thick) under optimal conditions were used to realize: a) very sensitive visible-blind UV-photodetectors with nanosecond response time; and b) single-crystal solar cells with ~21% power conversion efficiency. Unlike thin film polycrystalline solar cells, efficient cells with a grain-free single-crystal absorber are an ideal unobstructed system for investigating the device physics and chemistry of perovskites.

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