Michael Fayer, Doctoral Dissertation Advisor (AC)
Structured Perovskite Light Absorbers for Efficient and Stable Photovoltaics
Organic-inorganic hybrid lead-halide perovskite materials (ABX3 ) have attracted widespread attention in the field of photovoltaics owing to their impressive optical and electrical properties. However, obstacles still exist in the commercialization of perovskite photovoltaics, such as poor stability, hysteresis, and human toxicity. A-site cation engineering is considered to be a powerful tool to tune perovskite structures and the resulting optoelectronic properties. Based on the selection and combination of A-site cations, three types of perovskite structures, i.e., 3D perovskite, reduced-dimensional (2D/quasi-2D) perovskite, and 2D/3D hybrid perovskite can be formed. Herein, the remarkable breakthroughs resulting from these three perovskite structures are summarized, and their corresponding properties and characteristics, as well as their intrinsic disadvantages, are highlighted. By summarizing recent research progress, a new viewpoint for improving the performance and stability of perovskite photovoltaics is provided.
View details for DOI 10.1002/adma.201903937
View details for Web of Science ID 000533319000001
View details for PubMedID 32419234
Controlling the Dynamics of Ionic Liquid Thin Films via Multilayer Surface Functionalization.
Journal of the American Chemical Society
The structural dynamics of planar thin films of an ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmimNTf2) as a function of surface charge density and thickness were investigated using two-dimensional infrared (2D IR) spectroscopy. The films were made by spin coating a methanol solution of the IL on silica substrates that were functionalized with alkyl chains containing head groups that mimic the IL cation. The thicknesses of the ionic liquid films ranged from ∼50 to ∼250 nm. The dynamics of the films are slower than those in the bulk IL, becoming increasingly slow as the films become thinner. Control of the dynamics of the IL films can be achieved by adjusting the charge density on substrates through multilayer network surface functionalization. The charge density of the surface (number of positively charged groups in the network bound to the surface per unit area) is controlled by the duration of the functionalization reaction. As the charge density is increased, the IL dynamics become slower. For comparison, the surface was functionalized with three different neutral groups. Dynamics of the IL films on the functionalized neutral surfaces are faster than on any of the ionic surfaces but still slower than the bulk IL, even for the thickest films. These results can have implications in applications that employ ILs that have electrodes, such as batteries, as the electrode surface charge density will influence properties like diffusion close to the surface.
View details for DOI 10.1021/jacs.0c03044
View details for PubMedID 32349470
- Conjugated Alkylamine by Two-Step Surface Ligand Engineering in CsPbBr3 Perovskite Nanocrystals for Efficient Light-Emitting Diodes CHEMNANOMAT 2019; 5 (3): 318–22