First-principles study on photovoltaic properties of 2D Cs₂PbI₄-black phosphorus heterojunctions

Abstract

Both 2D perovskite Cs 2 PbI 4 and phosphorus are significant optoelectronic semiconductor materials, the optical-electrical characters between both contact interfaces are interesting topics. In present work, we demonstrate comparative investigation of optoelectronic properties for two kinds of electrical contact interfaces. i.e. Pb-I and Cs-I interfaces with black phosphorus contacts. The carrier transport, charge transferring and optical properties for both cases are investigated by using first principle calculation. Both contact interfaces exhibit type II band alignment with direct band gap. Charge carrier migration from Cs-I interface to black phosphorus is more strong than that of Pb-I interface by considering differential charge density and bader charge between distinct electrical contact interfaces. Besides, electron-hole effective masses of heterojunctions for both cases along different direction are investigated. Optical absorption coefficients of both cases are compared with those of free-standing Cs 2 PbI 4 and black phosphorus in the visible spectrum. We systematically compared advantages and disadvantages of two kinds of contact interfaces for photovoltaic application, and the results reveal interfacial engineering of 2D heterojunction plays a important role in tuning optoelectronic properties.

First-principles study on optoelectronic properties of Cs2PbX4–PtSe2 van der Waals heterostructures

“…In order to nd out the effect of halogen elements on Cs 46,47 With the halogen varying from Cl to I, the interface binding energies of Cs 2 PbX 4 -PtSe 2 heterostructures decrease rapidly and heterostructures become more stable in energy due to the lower interface binding energy. 48,49 .02 eV, and 1.29 eV, which approach optimal bandgap (1.34 eV) for solar cells. 54 Furthermore, the Mott-Wannier theory has been used to approximate exciton binding energies in 2D.…”

“… 46,47 With the halogen varying from Cl to I, the interface binding energies of Cs 2 PbX 4 –PtSe 2 heterostructures decrease rapidly and heterostructures become more stable in energy due to the lower interface binding energy. 48,49 Above all, the interlayer distance ranging from 2.76 Å to 2.91 Å belong to vdW and small interface binding energy revealed that 2D Cs 2 PbX 4 –PtSe 2 heterostructures are formed by vdW contact. The lattice mismatches of the 2D Cs 2 PbCl 4 –PtSe 2 , Cs 2 PbBr 4 –PtSe 2 and Cs 2 PbI 4 –PtSe 2 heterostructures in the a and b directions are less than 7.25%, 4.86% and 5.54%.…”

“…Correspondingly, the holes accumulate in Cs 2 PbX 4 monolayer and the electrons accumulate in PtSe 2 monolayer, leading to an increase of interface electric potential in Cs 2 PbX 4 monolayer and a decrease of this in PtSe 2 monolayer. 48,49 Therefore, the band edges of Cs 2 PbX 4 interface are bent upward and those of PtSe 2 interface are bent downward aer the contact of monolayer Cs 2 PbX 4 and PtSe 2 . The difference between the Fermi level and the vacuum level is dened as the work function, representing the binding capacity of electrons.…”

“…A larger DEP implies a powerful built-in electrostatic eld which could lead to carrier dynamics and charge transfer. 47,48 The DEP of Cs The optical properties of perovskites have an important inuence on the perovskite optoelectronic devices besides electronic structure. The optical absorption coefficients of single-layer PtSe 2 , single-layer Cs 2 PbX 4 , and corresponding heterostructures were calculated, as represented in Fig.…”

“…The Cs 2 PbBr 4 –PtSe 2 heterostructure is type-II level alignment which is conducive to spontaneously drive the holes and electrons generated by the photoelectricity to move forward in opposite directions. 48,49,57 However, the Cs 2 PbCl 4 –PtSe 2 and Cs 2 PbI 4 –PtSe 2 heterostructures are type-I level arrangement. Due to the type-II level alignment of Cs 2 PbBr 4 –PtSe 2 heterostructure, it is useful to charge separation and improve PCE performance of Cs 2 PbX 4 solar cells.…”