Researchers develop new predictive model for designing 2D perovskites

A study conducted by researchers at the Hanbat National University (HNU) in Daejeon, South Korea, has revealed a predictive model that enables rational design of two-dimensional perovskites after researchers examined how the dielectric screening environment governs excitonic properties.

The ‘Exciton Binding Energy Modulation in 2D Perovskites: A Phenomenological Keldysh Framework’ study published in Advanced Functional Materials, outlines their new insights into separating dielectric-screening effects from structural distortion, addresses a longstanding challenge in perovskite materials design.

HNU Department of Materials Science and Engineering Research Lead Professor Ki-Ha Hong said the study addresses a long-standing challenge in 2D pervoskite research.

“When the organic spacer is changed, the dielectric environment and the inorganic lattice structure often change at the same time, making it difficult to determine which factor actually controls the excitonic properties,” Hong said.

“To disentangle these effects, we used a homologous series of organic spacers and focused on a structurally consistent set of 2D perovskites in which the Pb–I framework remains nearly unchanged. This allowed us to isolate the role of dielectric screening in modulating the quasiparticle bandgap and exciton binding energy.” 

The study

The researchers isolated the effect of dielectric screening by fabricating structurally consistent 2D lead-iodide perovskites with systematically varied organic spacer lengths while minimising lattice distortions.

Direct spectroscopic measurements showed that quasiparticle bandgaps increased with spacer length, whereas exciton energies remained nearly constant, demonstrating that dielectric screening predominantly controls excitonic behaviour.

By introducing a modified Keldysh model incorporating a phenomenological dielectric function, the team achieved close agreement between theoretical predictions and experimental data, providing an experimentally validated framework for predicting excitonic properties.

“Our model offers a practical design rule for predicting how organic spacer length controls excitonic properties of 2D perovskites. This provides a molecular-level design rule for tuning exciton binding energy and energy levels in 2D perovskites, which can guide future design of light-emitting, photovoltaic, and other optoelectronic materials,” Hong said.