Triple Halide Ultrawide Bandgap Metal Halide Perovskites

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

Non-technical Description Metal halide perovskites are solution-processed semiconductors with attractive optical and electronic properties, which have enabled the fabrication of efficient and low-cost devices such as solar cells and light-emitting diodes (LEDs). Perovskites used in the most efficient devices to date absorb light in the red and near-infrared. This corresponds to a band gap of 1.2 to 1.8 electron volts (eV), with an eV being the amount of energy needed to move an electron across an electric potential of one volt. It is desirable to develop high quality materials with higher band gaps to capture more of the sun’s energy in a solar cell or emit green or blue light from an LED. The team hypothesizes that perovskites with three different halide atoms could realize these high-quality materials with increased band gaps. The team will fabricate triple-halide perovskites and thoroughly characterize their structure, composition and properties. In doing so the team will expand the range of viable perovskites for device applications. This work will be done collaboratively between the University of Colorado Boulder and Wellesley College. Wellesley College is a diverse women’s undergraduate college, where a majority of the incoming class identifies as people of color. Wellesley College undergraduates work closely with researchers at major academic institutions and national laboratories. This greatly increases their research opportunities and provides students with exposure to graduate programs. This project will serve to support that population and expand STEM opportunities. Technical Description The goal of this project is to synthesize high performance all-inorganic perovskite semiconductors with bandgaps between 1.9 and 2.1 eV. The performance of current wide bandgap perovskites is limited by non-radiative recombination and environmental instability. Triple halide perovskites are hypothesized to have desirable properties because there will be no opportunity for demixing to occur at the A-site, chlorine will passivate defects, the small lattice parameter will result in strong bonds and there will be no organic cation that could decompose. The team will investigate a range of promising triple halide perovskites, leveraging its expertise to characterize and understand the miscible composition space; map and understand the instabilities in these materials; and ultimately quantify and optimize the optoelectronic properties of select triple halide perovskites. The team will determine how solution chemistry impacts perovskite nucleation, film growth and performance and resultant optoelectronic properties and stability. The team will document improvements using cyclic voltammetry, in situ photoluminescence and absorption spectroscopy, and X-ray diffraction to map defect densities and barriers to degradation. This project is working towards (1) optimized synthesis of novel triple halide perovskites; (2) quantification of the stability of wide bandgap perovskites and optoelectronic performance; and (3) improved interfacial layers for surface passivation and carrier selection in wide bandgap perovskites. 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.