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Metal halide perovskite materials are considered to be one of the most promising semiconductor materials and have broad application prospects in the fields of light-emitting diodes (LED), solar cells, and lasers
.
In the field of perovskite optoelectronic devices, the introduction of additives for defect passivation (such as passivation of vacancy defects: similar to a crystal with some missing parts, which can be filled by additive molecules) is an effective strategy to achieve high-quality perovskite materials.
However, there is still a lack of in-depth understanding about the influence of additives on the formation process of perovskite crystals
In view of the unclear status of how additives induce perovskite materials to form high-quality crystals, the research team found through research that the crystallization process of perovskite is determined by the interaction between the additive and the formamide iodide (FAI) in the precursor solution.
Of
.
"Additives containing amino groups (-NH₂) can form an intermediate structure with FAI and deplete the free FAI in the precursor.
This will facilitate the growth of perovskite crystals from the surface of the solution in the initial stage of the solution method, and finally the annealing During the process (that is, the process of volatilizing the liquid in the film during high-temperature heating), vertically-oriented perovskite crystals with high crystallinity and few grain boundaries are formed
.
" Professor Wang Nana said, on the contrary, it interacts more with formamide iodine.
Weak additives, such as carboxyl molecules, have little effect on the crystallization process, mainly to passivate the defects of the halide vacancies and fill some missing parts on the crystal
Based on this knowledge, the researchers designed a new type of additive molecule with amino and carboxyl bifunctional groups, and the prepared near-infrared perovskite LED device has an external quantum efficiency of 22.
2%, which once again refreshed the efficiency record of the perovskite LED
.
"By adding a new type of multifunctional additive, the crystallization process can be controlled and various defects on the crystal can be filled, thereby greatly improving the efficiency of the device
.
More importantly, this research also provides a universal method for additive screening, which is of great significance to the realization of high-performance perovskite optoelectronic devices.
The functional groups that passivate defects, on the other hand, need to have functional groups similar to amino groups to allow the perovskite crystals to grow vertically, so that the quality of the crystal growth can be higher
.
" Professor Wang Jianpu said
.
