Beam Geometry-Controlled Nonequilibrium Formation of WS2/CsPbBr3 Hybrids and Interfacial Carrier Dynamics

TL;DR

This study introduces a scalable laser ablation method using Gaussian and Bessel beams to synthesize WS2/CsPbBr3 nanocomposites with controlled defect levels and interfacial carrier dynamics, advancing low-dimensional optoelectronic materials.

Contribution

It demonstrates geometry-dependent femtosecond laser ablation for defect-controlled WS2 exfoliation and hybrid formation, revealing how beam profile influences carrier dynamics and interfacial properties.

Findings

Bessel beams reduce defect formation and enhance excitonic stability.

Hybrid structures exhibit Type-I band alignment and efficient interfacial carrier injection.

Transient absorption shows prolonged carrier lifetime in Bessel-processed samples.

Abstract

Perovskite based nanocomposites provide a versatile platform for tailoring light matter coupling and carrier injection in low dimensional optoelectronics. In particular hybrid structures incorporating transition metal dichalcogenides (TMDCs) enable tunable band alignment and excitonic dynamics. However, the central challenge lies in the scalable synthesis of defect controlled layered TMDCs suitable for coherent interfacial coupling. Here we demonstrate geometry dependent femtosecond (fs) laser ablation in liquid as a scalable strategy for defect controlled exfoliation of WS2 and in situ formation of WS2/CsPbBr3 nanocomposite. Using 50 fs pulses at identical fluence, we directly compare Gaussian and Bessel beam profiles to elucidate how spatial energy distribution governs nonlinear carrier generation, Coulomb stress and electron-lattice energy transfer. Multiphysics modeling combining nonlinear absorption, Coulomb instability criteria and two temperature dynamics reveals that the axially extended, weakly diffracting Bessel profile excites carrier densities above the electronic destabilization threshold while reducing the peak lattice heating. In contrast, Gaussian excitation concentrates energy within the focal volume, promoting rapid thermalization and defect formation. Spectroscopic analysis reveals reduced trap assisted recombination and enhanced excitonic stability in Bessel processed samples. Transient absorption spectroscopy (TAS) further demonstrates prolonged carrier lifetime. Extending this approach, single step ablation yields WS2/CsPbBr3 hybrids exhibiting Type-I band alignment and geometry dependent interfacial carrier injection, evidenced by photoluminescence quenching and modified ultrafast decay dynamics.