Lateral epitaxial grown of two-dimensional halide perovskite heterostructures
Cheng-Rui Shao Wei Hu
School of Physics and Electronics,Hunan University
作者简介：*Wei Hu e-mail:huwei@hnu.edu.cn;
Lateral epitaxial grown of two-dimensional halide perovskite heterostructures
Cheng-Rui Shao Wei Hu
School of Physics and Electronics,Hunan University
In last decade,the halide perovskite materials have been widely explored all over the world for their excellent optoelectronic properties.The perovskite solar cells in particular are reshaping the landscape of photovoltaic.Meanwhile,the perovskites have remarkable performance in photon detection,light-emitting,medical detection and other optoelectronic devices
[
1,
2]
.However,there are lots of deeper research works requiring to be performed in order to realize perovskite materials commercial applications in near future.For example,the controllable preparation of perovskite heterostructure is essential urgently for an optoelectronic device construction.At present,the preparation processes for polycrystalline and single crystal perovskite materials have been generally discussed.The synthesis of polycrystalline perovskite is relatively easy to operate and achieve
[
3]
.The growth of perovskite single crystal is usually carried out in supersaturated solutions,and the perovskite crystals owning single component only have been studied by many researchers
[
4]
.In the solution containing different precursors,a perovskite crystal with fixed ion hybridization ratio is obtained in generally.A perovskite heterostructure with different components can also be obtained,but it cannot exist stably due to the strong ion migration in perovskite materials.It is a great challenge for the controllable growth of a perovskite heterostructure at atomic level.
Recently,the different perovskite structures were achieved in a research work reported by Dou et al.
[
5]
They presented new cationic groups 2T+(bithiophenylethylammonium),which own larger organic cationic aiming to form the quasitwo-dimensional perovskite structure (Fig.1 a,b).This design is similar to a number of cationic groups (BA+,EA+,PEA+)reported before
[
6,
7]
.During growth of the low-dimensional perovskite,a thin layer of quasi-two-dimension structure is firstly formed,which is closely attached to the substrate surface.The researchers then used a larger organic ion (2T+)skeleton to form a more rigid thin coating.Compared with B A+,this organic ion forms a more powerful restric tion on the lateral ion migration of the crystal structure.As a result,the precipitation sequence was successively pided due to the solubility difference between the two perovskite components.The heterostructure perovskite was spontaneously formed finally,as shown in Fig.1f,which was well stabilized by the organic skeleton.The authors mentioned in the paper that after heating at 100℃over 1 h,the heterojunction still maintains a very good interface sharpness (Fig.1g).The corresponding BA+components with a small organic skeleton did not maintain the sharpness of the interface under the same conditions (Fig.1h).The researchers carried out the following theoretical simulation in order to understand the superior of the synthesized material.After calculation,the results shew that the constructed perovskite crystal with 2T skeleton had a larger energy barrier to form halogen vacancy,and fewer halogen vacancies compared with the perovskite crystal with BA skeleton (Fig.1i).Hence,the ion migration in this perovskite crystal was found to be greatly limited.At the end of this work,the researchers used this idea to grow many times and obtained many different lattice structures,which is a major breakthrough for the growth of traditional perovskite crystals.
In the study of perovskite single crystal growth,the strategy is usually complex and difficult because of the mixed precursor solution system.In this work,the researchers successfully investigated the inhibition of growth and ion migration of perovskite heterojunction by using a combination of simulation and experimental results.A novel fabrication direction is given for the regulation of perovskite growth,which can be used for reference in device design and practical application in the future.At the same time,the addition of long-chain macromolecular organic groups will also sacrifice the photoelectric efficiency of many perovskites and the larger lattice dislocation,which will also be one of the challenges that perovskites will face in the future.
Fig.1 Schematic illustrations and proposed band alignments of a (2T)2PbBr4-2T2PbBr4 and b (BA)2PbBr4-BA2PbBr4 lateral heterostructures;c optical and d photoluminescence images of a (2T)2PbBr4-2T2PbBr4 lateral heterostructure;e optical and f photoluminescence images of a (BA)2PbBr4-BA2PbBr4 lateral heterostructure;g and h photoluminescence image of (2T)2PbBr4-2T2PbBr4 and (BA)2PbBr4-BA2PbBr4;i free energy for removing a halide atom from an apical position to vacuum to generate a halide vacancy (Reproduced from Ref.
[5].Copyright Spring Nature)
