Keenan Wyatt

Keenan Wyatt is a graduate student at the University of Colorado Boulder studying materials science under the guidance of Michael Toney. As an IRES student he will work in Antonio Abate’s group, with Zafar Iqbal as a mentor, investigating all-inorganic perovskite chemistries and how modifying variables in the precursor ink affects the perovskite film quality.

Graduate Advisor: Mike Toney (University of Colorado Boulder)
IRES-Perovskites Host: Antonio Abate (Helmholtz Zentrum Berlin)

Open Air Stability of DMAI Modified CsPbI₃ Perovskite Films

Cesium lead triiodide (CsPbI₃) is a sought-after composition for perovskite solar cells because of its ideal bandgap for tandem applications (~1.7 eV) and its simplified composition for improved homogeneity. The instability of CsPbI₃ metal halide perovskites remains a major obstacle to their commercial deployment in optoelectronic devices. Dimethylammonium iodide (DMAI) is often incorporated to stabilize the crystal structure, but its persistence after annealing and its impact on phase stability remain debated. In this work, we investigate the open-air stability of perovskite films prepared from three DMA-modified chemistries—Cs(DMA)PbI₄, Cs₀.₇DMA₀.₃PbI₃, and Cs₀.₆DMA₀.₄PbI₃—processed under varied solvent systems, antisolvent treatments, and annealing temperatures. Air-exposed control films of Cs(DMA)PbI₄ in DMF rapidly converted to the non-perovskite δ-phase within minutes, with photoluminescence (PL) and XRD data indicating surface-initiated degradation. The Cs₀.₇DMA₀.₃PbI₃ films prepared without antisolvent showed improved stability and phase purity (single PL emission at ~1.688 eV) but suffered from a discontinuous microstructure. Increasing the DMA fraction to 0.4 and lowering annealing temperature yielded further gains in visual air stability, with the most stable film produced at 70 °C for 600 s. While none of the compositions exhibited long-term resistance to oxygen and moisture, compositional tuning combined with solvent and thermal control delayed visual degradation providing insight for processing strategies of CsPbI₃-based devices.