| 1. |
- Cai, Weidong, 1991-, et al.
(författare)
-
Chirality Induced Crystal Structural Difference in Metal Halide Composites
- 2022
-
Ingår i: Advanced Optical Materials. - : Wiley-V C H Verlag GMBH. - 2162-7568 .- 2195-1071. ; 10:16
-
Tidskriftsartikel (refereegranskat)abstract
- Incorporating chiral organic compounds into metal halide frames is a common and useful method to introduce chirality in metal halide composites. The structures of resulting racemic and chiral composites are usually considered to be nearly identical owing to similar chemical bonding. In this work, by incorporating chiral MBABr (bromide methylbenzylamine) into an inorganic frame, a significant crystallization difference between the resulting racemic and chiral metal halide composites is observed, as confirmed by both structural and spectroscopic measurements. In addition, the structural transformation in the chiral composites can also be induced by moisture, ascribed to the asymmetric hydrogen bonding in chiral materials. These results provide new insights for the future synthesis of chiral materials and open up new possibilities to advance the materials functionalities.
|
|
| 2. |
- Cai, Weidong, 1991-
(författare)
-
Tunning Multicolor Light Emission in Lead-free Materials
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Perovskites are a class of compounds with the general formula ABX3 and becoming increasingly attractive recently. Because this kind of material possesses various advantages such as abundant raw materials, easy synthesis, excellent photoelectric properties, and short production process. As one of the applications for lead-based perovskites, the perovskite solar cells have quickly enhanced their PCE from 3.8% in 2009 to over 25% within a short period. However, the problems, such as instability of the ionic crystal nature and toxicity of lead, largely hinder the lead-based perovskites towards commercialization. Therefore, it is necessary to develop new lead-free materials as alternative to lead-based perovskites, where similar structures can be formed to inherit the excellent optoelectronic properties. Moreover, new properties can be achieved due to more abundant metal candidates in lead-free materials. Based on this, we develop different kinds of perovskite-structure-like lead-free materials such as organic inorganic hybrid materials, chiral materials and double perovskites. In addition to physical and chemical properties like photoluminescence, absorption, structure, etc., we further demonstrate their potential applications according to their unique properties such as multicolor light emission.We incorporate chiral MBA (methylbenzylamine) in inorganic metal system to obtain chiral lead-free organic inorganic hybrid materials, where significant crystallization difference is observed between rac and chiral halide compounds for the first time. Such difference is confirmed by spectrum and structural results. What’s more, we find that moisture can cause the structural transfer in chiral compounds, attributed to the asymmetric hydrogen bonding of chiral compounds. Our achievements open up new chance to improve our material property and provide new horizon for synthesis of chiral materials in the future.Then, we obtained blue emission center in Mn-based organic and inorganic compounds by choosing organic molecule MBA. The method has basic difference with the emissions in Mn based compounds. The coexisting two emission centers of our Mn based samples is verified by spectral results. Because two emission centers can induce different PL excitation responses, so that the excitation wavelengths are capable of manipulating the emission color. Specifically, we achieve CIE coordinates of (0.33, 0.35) with a white emission. The potential of our materials in anti-counterfeiting and multicolor lighting technology are further demonstrated. Our accomplishments explore a new approach for multicolor emission in Mn based materials.We finally obtained Sb3+/Cu+ co-doped Cs2NaInCl6 (CNIC) double perovskite by hydrothermal reaction which exhibits tunable dual emissions with PL quantum efficiency (PLQE) of 78%. Depending on different photoluminescence excitation (PLE) spectra between two emissions, multiple emission colors can be got by manipulating excitation wavelength. Interestingly, emission color gamut can be further tuned through manipulating the feeding ratio of CuI dopant, where warm color and cool color can be achieved separately. We further illustrated the application potential of our co-doped materials in the fileds of multicolor lighting devices and anti-counterfeiting. Our achievements open up a brand-new strategy for wider spectral luminescence of double perovskites and pace up the road for a series of new applications.
|
|
| 3. |
- Qin, Jiajun, et al.
(författare)
-
From optical pumping to electrical pumping: the threshold overestimation in metal halide perovskites
- 2023
-
Ingår i: Materials Horizons. - : ROYAL SOC CHEMISTRY. - 2051-6347 .- 2051-6355. ; 10:4, s. 1446-1453
-
Tidskriftsartikel (refereegranskat)abstract
- The threshold carrier density, conventionally evaluated from optical pumping, is a key reference parameter towards electrically pumped lasers with the widely acknowledged assumption that optically excited charge carriers relax to the band edge through an ultrafast process. However, the characteristically slow carrier cooling in perovskites challenges this assumption. Here, we investigate the optical pumping of state-of-the-art bromide- and iodine-based perovskites. We find that the threshold decreases by one order of magnitude with decreasing excitation energy from 3.10 eV to 2.48 eV for methylammonium lead bromide perovskite (MAPbBr(3)), indicating that the low-energy photon excitation facilitates faster cooling and hence enables efficient carrier accumulation for population inversion. Our results are then interpreted due to the coupling of phonon scattering in connection with the band structure of perovskites. This effect is further verified in the two-photon pumping process, where the carriers relax to the band edge with a smaller difference in phonon momentum that speeds up the carrier cooling process. Furthermore, by extrapolating the optical pumping threshold to the band edge excitation as an analog of the electrical carrier injection to the perovskite, we obtain a critical threshold carrier density of similar to 1.9 x 10(17) cm(-3), which is one order of magnitude lower than that estimated from the conventional approach. Our work thus highlights the feasibility of metal halide perovskites for electrically pumped lasers.
|
|
