Data-driven discovery of high performance layered van der Waals piezoelectric NbOI2

TL;DR

This study uses high-throughput calculations to identify NbOI2 as a top layered van der Waals material with exceptional piezoelectric properties, verified experimentally, and explores its atomic origins and potential for flexible devices.

Contribution

It introduces NbOI2 as the highest-performing 2D piezoelectric material discovered through computational screening and experimental validation.

Findings

NbOI2 has the largest piezoelectric stress coefficient among 2D materials.

Experimental studies confirm strong piezoelectric responses exceeding known references.

Atomic insights reveal bond covalency and structural distortions influence piezoelectric and ferroelectric behaviors.

Abstract

Using high-throughput first-principles calculations to search for layered van der Waals materials with the largest piezoelectric stress coefficients, we discover NbOI2 to be the one among 2940 monolayers screened. The piezoelectric performance of NbOI2 is independent of thickness, and its electromechanical coupling factor of near unity is a hallmark of optimal interconversion between electrical and mechanical energy. Laser scanning vibrometer studies on bulk and few-layer NbOI2 crystals verify their huge piezoelectric responses, which exceed internal references such as In2Se3 and CuInP2S6. Furthermore, we provide insights into the atomic origins of anti-correlated piezoelectric and ferroelectric responses in NbOX2 (X = Cl, Br, I), based on bond covalency and structural distortions in these materials. Our discovery that NbOI2 has the largest piezoelectric stress coefficients among 2D materials calls for the development of NbOI2-based flexible nanoscale piezoelectric devices.