Catalyst Project: Age and temperature-dependent millimeter-wave charge carrier dynamics in hybrid perovskite films

Catalyst Projects provide support for Historically Black Colleges and Universities (HBCU) to work towards establishing research capacity of faculty to strengthen science, technology, engineering, and mathematics (STEM) undergraduate education and research. It is expected that the award will further the faculty member's research capability, improve research and teaching at the institution, and involve undergraduate students in research experiences. This award to North Carolina Central University supports faculty and undergraduate research experiences investigating the effects of aging and temperature on hybrid organic-inorganic perovskites to predict charge carrier density. Specifically, the project seeks to utilize high-throughput testing and a machine learning algorithm for data analyses to understand aging related stability and the causes of degradation of organometallic halide perovskites.Perovskite in 3-D form is a very attractive material for applications such as a field-effect transistor (FET), light-emitting diodes (LED), photo- and radiation detection, scintillation, biochemical applications, and has direct industrial application for hydrogen production. Since monomolecular (trap-assisted) recombination trends in methylammonium lead-halide (MAL3I) and its cation engineered variants can be directly measured using the time-resolved microwave conductivity (TRMC) measurements, this project aims to use a free-space time-resolved millimeter-wave conductivity apparatus (TR-mmWC), developed at NCCU, to observe the age-peak voltage and non-radiative age-recombination decay trends in MAL3I and its structural variants at different exposure temperature regimes. The experimental data collection and analysis will help inform two questions: (1) Does the sample develop shallow defects over time for a better charge transport with aging, or does the reverse process hold? and (2) How do the positive peak and negative photoconductivity behave in an hybrid organic (MA) – inorganic (L3I) system? These studies have the potential to reveal the frequency dependence of electromagnetic interaction with material dielectric properties and conductivity, and the systematical collection of frequency-swept absorption profiles in a large temperature range, demonstrating how the charge dynamical properties at millimeter-wave frequencies change by age at different temperatures.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.