A density functional theory study on the interface stability between CsPbBr3 and CuI

Eric W Welch,Luisa Scolfaro,Young-Kwang Jung,Aron Walsh,Alex Zakhidov

doi:10.1063/5.0018925

Eric W Welch, Luisa Scolfaro + Show 3 more

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https://doi.org/10.1063/5.0018925

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Abstract

This paper assesses the interface stability of the perovskite CsPbBr3 and transport layer CuI using density functional theory and band offset calculations. As a low-cost, more stable alternative to current hole transport materials, CuI may be used to template the epitaxial growth of perovskites such as CsPbBr3 owing to a 1% lattice constant mismatch and larger bulk modulus. We compare all eight atomic terminations of the interfaces between the (100) low-energy facet for both CsPbBr3 and CuI, increasing material thickness to consider charge density redistribution and bonding characteristics between surface and bulk-like regions. A low energy atomic termination is found to exist between these materials where alternating charge accumulation and depletion regions stabilize bonds at the interface. Band offset calculations reveal a type I straddling gap offset in the bulk shifting to a type II staggered gap offset as the thickness of the materials is increased, where the built-in potential changes as layer thickness increases, indicating the tunability of charge separation at the interface. CuI may, thus, be used as an alternative hole transport layer material in CsPbBr3 optoelectronic devices.

Highlights

Hybrid perovskites (HPs) are promising emissive layer materials in optoelectronic devices (OEDs)
We report here on density functional theory calculations of the (100) surface energies, interface energies, charge density differences, local potential differences, and valence band offset (VBO) and conduction band offset (CBO) for the novel system of CuI as a hole transport layer (HTL) in a CsPbBr3 light emitting device
A Birch–Murnaghan39 fit to the data reveals a near perfect agreement between experiment and theory for the equilibrium lattice constant in CsPbBr3 (5.88 Å) and a 2% difference between the experimental and theoretical equilibrium lattice constant in CuI (5.95 Å); this discrepancy is attributed to the use of semi-local exchange-correlation functionals in this study

Summary

Introduction

Hybrid perovskites (HPs) are promising emissive layer materials in optoelectronic devices (OEDs). Their inclusion in photovoltaics, light emitting diodes, lasers, and photodetectors has revolutionized each respective field. HP OEDs do, require the inclusion of charge transport layers to inject/remove requisite mobile electrons/holes, as HPs are intrinsic semiconductors with no majority free charge carrier. The current hole transport layer materials in use, are expensive (e.g., Spiro-OMETAD) or acidic (e.g., PEDOT:PSS) and potentially contribute to device instability without added processing steps such as acidity suppression; it should be noted that there are numerous candidates for inexpensive and stable electron transport layer materials. Density functional theory studies on interfaces between perovskites and transport layers may be used to predict stable, efficient materials for HP OEDs. To combat the high cost and acidity issues inherent in current

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