AI Article Synopsis
- Low-dimensional hybrid perovskites are receiving attention for their adjustable optoelectronic properties and stability, with the organic spacer playing a crucial role in their optimization.
- The study focuses on the effects of substituting hydrogen with fluorine in alkylammonium organic cations, specifically observing optical changes in 2D perovskite films resulting in a 0.2 eV blue-shift in excitonic position.
- Findings indicate that fluorination enhances structural rigidity and stability at room temperature, reducing the likelihood of phase transitions, which suggests that small structural changes can significantly impact the robustness and performance of 2D perovskites for future optoelectronic applications.
Article Abstract
Low-dimensional hybrid perovskites have triggered significant research interest due to their intrinsically tunable optoelectronic properties and technologically relevant material stability. In particular, the role of the organic spacer on the inherent structural and optical features in two-dimensional (2D) perovskites is paramount for material optimization. To obtain a deeper understanding of the relationship between spacers and the corresponding 2D perovskite film properties, we explore the influence of the partial substitution of hydrogen atoms by fluorine in an alkylammonium organic cation, resulting in (Lc)PbI and (Lf)PbI 2D perovskites, respectively. Consequently, optical analysis reveals a clear 0.2 eV blue-shift in the excitonic position at room temperature. This result can be mainly attributed to a band gap opening, with negligible effects on the exciton binding energy. According to Density Functional Theory (DFT) calculations, the band gap increases due to a larger distortion of the structure that decreases the atomic overlap of the wavefunctions and correspondingly bandwidth of the valence and conduction bands. In addition, fluorination impacts the structural rigidity of the 2D perovskite, resulting in a stable structure at room temperature and the absence of phase transitions at a low temperature, in contrast to the widely reported polymorphism in some non-fluorinated materials that exhibit such a phase transition. This indicates that a small perturbation in the material structure can strongly influence the overall structural stability and related phase transition of 2D perovskites, making them more robust to any phase change. This work provides key information on how the fluorine content in organic spacer influence the structural distortion of 2D perovskites and their optical properties which possess remarkable importance for future optoelectronic applications, for instance in the field of light-emitting devices or sensors.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6999157 | PMC |
| http://dx.doi.org/10.3389/fchem.2019.00946 | DOI Listing |
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