No abstract

Controlling effective separation of carriers at the interface is a key element to realize highly efficient halogenated perovskite-based optoelectronic devices. Here, a comprehensive study of interfacial properties for CsPbBr 3 nanocrystals (NCs)/graphene heterostructure is performed by the combination of theoretical and experimental methods. Enhanced visible light absorption is observed experimentally in the CsPbBr 3 NCs/graphene heterostructure. The strong photoluminescence quenching phenomenon and improved photoresponse prove the efficient interfacial charge transfer from the perovskite CsPbBr 3 NC layer to the graphene side. Significantly, theoretical calculations suggest that an intrinsic built-in electric field, pointing from graphene toward CsPbBr 3 , promotes the separation of photoinduced carriers at the CsPbBr 3 NCs/graphene interface and simultaneously inhibits the recombination of electron−hole pairs. Thus, the high optoelectronic performance can be obtained in the CsPbBr 3 NCs/ graphene heterostructure, as shown in our experiment. Moreover, the CsPbBr 3 NCs/graphene heterostructure exhibits smaller effective mass than that of CsPbBr 3 NCs, indicating that the heterostructure does possess a high carrier mobility, which can further accelerate the separation of photogenerated carriers. Furthermore, the calculated results reveal that, accounting for the presence of the stronger built-in electric field, larger band bending value, and smaller effective mass, the PbBr 2 /graphene interface can realize the separation of the photoinduced carriers more effectively than the CsBr/graphene interface and thus more efficiently facilitate electron transfer from the perovskite optical absorber side to the graphene electronic transport side. Our findings provide valuable insight into perovskite/graphene-based photodetector devices via the interface engineering project.

The NO gas adsorption properties of the monolayer, bilayer and trilayer MoS2 has been studied based on the first-principles calculation. The interaction between NO and MoS2 layers is weak physical adsorption, which is evidenced by the large distance (>3 Å), small adsorption energies (<0.9 eV) and deformation electron density. Moreover, the effect of the NO adsorption on the charge transfer and the electronic properties are also discussed. For all the NO adsorption cases, 0.04 e charge transfer exists by Mulliken/Hirshfeld analysis and and the charge density difference between NO molecular and MoS2 layers. The NO adsorption can obviously induces new impurity states at about 0.5 eV in the band gap that can lead to the change of the transport properties of the MoS2 layers and then it could detect the NO gas. We also performed semi-quantitatively theoretical analysis from the carrier concentration n and carrier mobility μ to obtain the effect of the NO adsorption on electrical conductivity. Our results provide a theoretical basis for the application of MoS2 layers as gas sensors for important NO polluting gases in air.

No abstract

Stacking sequences, external strain and a vertical electric field can be used to effectively modulate the electronic structures of graphyne-based homo- and hetero-structures.