How Methylammonium Cations and Chlorine Dopants Heal Defects in Lead Iodide Perovskites
Despite rapid progress in the efficiency of organohalide perovskite based solar cells, physical mechanisms underlying their efficient charge separation and slow charge recombination still elude us. Using a newly developed computational tool, we showed in this work that lead and iodine vacancies in lead tri-iodide methylammonium (MAPbI3) perovskite could yield deep trap states. Remarkably, these detrimental trap states could be healed by dynamics of the methylammonium cations, rotating in response to point charges, as well as slight changes in chemical composition with a tiny amount of chlorine dopants. The theoretical findings were confirmed by photoluminescence experiments and paved the way toward the design of defect-free perovskite materials with optoelectronic performance approaching the theoretical limits. The work suggests that treating electron–hole and electron–nuclei interactions on the same footing is crucial to elucidating photo-physics of the perovskite materials.
Publication: G. Nan, et al. Adv. Energy Mater. 8, 1702754 (2018).
Computational Research and Education for Emergent Materials
(Left) CSUN PREM students participated the REU program at Princeton in the summer 2017. These students were housed on the Princeton campus and benefitted both from formal REU program events and from interaction with a larger group of REU students. The CSUN students were supervised by Princeton faculty members and their graduate students to carry out various research projects in Materials Science and Engineering.
(Below) We have organized a research symposium hosted by the Department of Physics and Astronomy at CSUN in March 2018 where the PREM students presented their research results in the form of posters. The goal of the symposium was to showcase the research accomplishments of the PREM program, exchange ideas, and foster collaborations.