The solution accessibility of hybrid perovskites makes it possible to obtain their large crystals at low cost, which offers opportunities to incorporate crystal out-of-plane anisotropy for polarization-sensitive photodetection. However, limited by the absorption anisotropy of the material structure, polarization sensitivity of such a device remains low. Thus, a new strategy to design 2D hybrid perovskites with large anisotropy for polarization-sensitive photodetection is urgently needed. 

Heterostructures provide a clue to address this issue. On one hand, construction of heterostructures can improve the optical absorption and free-carrier densities of the composite. On the other hand, the built-in electric field at the heterojunction can spatially separate the photogenerated electron-hole pairs, significantly reducing the recombination rate and further enhancing the sensitivity for polarization-sensitive photodetectors. Therefore, constructing single-crystalline heterostructures of anisotropic 2D hybrid perovskites would realize devices with high polarization sensitivity.  

In a study published in National Science Review, the research group led by Prof. LUO Junhua from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences developed a 2D/3D heterostructure crystal, combining the 2D hybrid perovskite with its 3D counterpart, and achieve polarization-sensitive photodetection with record-high performance.  

The researchers developed devices based on the heterostructure crystal which deliberately leverage the anisotropy of 2D perovskite and the built-in electric field of heterostructure, permitting the first demonstration of a perovskite heterostructure-based polarization-sensitive photodetector that operates without the need for external energy supply.  

Notably, the polarization sensitivity of the device surpasses all of the reported perovskite-based devices, and can be competitive with conventional inorganic heterostructure-based photodetectors.  

Further studies revealed that the built-in electric field formed at the heterojunction can efficiently separate those photogenerated excitons, reducing their recombination rate and therefore enhancing the performance of the resulting polarization-sensitive photodetector. 

High polarization sensitivity up to 17.6 is achieved in self-driven polarization-sensitive photodetector based on a single-crystalline 2D/3D hybrid perovskite heterostructure which is grown via a delicate solution method. This study expands the range of choices of materials that can be used for high-performance polarization-sensitive photodetectors, and correspondingly, the design strategies. 

Illustration of the Research (Image by Prof. LUO’s group)