Chemical Composition and Phase Evolution in DMAI-Derived Inorganic Perovskite Solar Cells

Abstract

Inorganic CsPbI 3 is promising to enhance the thermal stability of perovskite solar cells. The dimethylamine iodide (DMAI) derived method is currently the most efficient way to achieve high efficiency, but the effect of DMAI has not been fully explained. Herein, the chemical composition and phase evolution of the mixed DMAI/CsPbI 3 layer during thermal treatment has been studied. The results demonstrate that, with the common DMAI/CsI/PbI 2 recipe in DMSO solvent, a mixed perovskite DMA 0.15 Cs 0.85 PbI 3 is first formed through a solid reaction between DMAPbI 3 and Cs 4 PbI 6 . Further thermal treatment will transform the mixed perovskite phase directly to γ-CsPbI 3 and then spontaneously convert to δ-CsPbI 3 . It has been also demonstrated that the DMA 0.15 Cs 0.85 PbI 3 phase is thermodynamically stable and shows a bandgap of 1.67 eV, which is narrower than 1.73 eV of γ-CsPbI 3 . The device efficiency of the mixed DMA 0.15 Cs 0.85 PbI 3 perovskite is therefore highly improved in comparison with the pure inorganic γ-CsPbI 3 perovskite.

Managing Phase Purities and Crystal Orientation for High‐Performance and Photostable Cesium Lead Halide Perovskite Solar Cells

“…By integrating the organic cation dimethylammonium (DMA + ) into the precursor solution of CsPbI 3 perovskite, crystallization of the tetragonal ( β ) phase of CsPbI 3 perovskite can be improved, and the phase better stabilized . DMA + in CsPbI 3 would beneficially increase the Goldschmidt tolerance factor, however, whether it remains in the resultant film is still debated and is likely annealing temperature‐dependent . An alternative strategy to achieve stability is through halide alloying with bromide in CsPbI 3 − x Br x compositions, which has the further advantage of optical bandgap tenability across a range of phase‐stable perovskite compositions (in an inert atmosphere at room temperature) .…”

Chemically Stable Black Phase CsPbI3 Inorganic Perovskites for High‐Efficiency Photovoltaics

“…Therefore, several works suggested that the CsPbI 3 inorganic perovskite fabricated by the HPbI 3 method may lead to the formation of the hybrid perovskite of Cs 1− x DMA x PbI 3 . [ 55–57 ] However, the UV–vis absorbance spectra of these Cs 1− x DMA x PbI 3 with different claimed DMA contents are similar to each other. Recently, Wang et al.…”

Efficient and Stable All‐Inorganic Perovskite Solar Cells

“…Finally, the device with HI delivered a high PCE of 17.3%. As the intermediate phase was DMAPbI 3 or DMAI/DMAPbI x after HI was introduced, Pang and coworkers [77] directly incorporated DMAI into CsPbI 3 precursor solution to prepare phase-stable and high-quality perovskite films. As shown in Figure 10a, it was revealed that DMAPbI 3 and Cs 4 PbI 6 were first formed when films were annealed at 100 C for 10 min and then converted into mixed-cation perovskite phase DMA 0. was directly transformed into γ-CsPbI 3 and then was spontaneously converted into δ-CsPbI 3 .…”

“…However, the influence mechanism of DMAI residue for device stability was not revealed in this work, which remains investigated deeply in the subsequent research work. Although huge progresses have been achieved on DMAI, inconsistent conclusions were obtained on its role of DMAI as an additive [12,22,117] or dopant, [77,109] which could be ascribed to different annealing temperatures and times along with different amounts of DMAI and preparation condition (e.g., humidity, oxygen, etc. ).…”