An Integrated DFT-FDTD Design of Plasmon-Enhanced Lead-Free $CsSn$$_x$$Ge$$_{1-x}$$I$$_3$ Perovskite LEDs

Shoumik Debnath; Sudipta Saha; Khondokar Zahin; Ying Yin Tsui; Md. Zahurul Islam

doi:10.1039/D6MA00110F

paper

An Integrated DFT-FDTD Design of Plasmon-Enhanced Lead-Free $C s S n$ $_{x}$ $G e$ $_{1 - x}$ $I$ $_{3}$ Perovskite LEDs

arXiv:2512.17467 · doi:10.1039/D6MA00110F

Abstract

CsSn $_{x}$ Ge $_{1 - x}$ I $_{3}$ as lead-free perovskites are promising for next generation NIR emitting perovskite LEDs due to their tunable bandgaps and stability. However, they suffer from poor light extraction efficiency, and accurate composition-specific optical data for these materials remain scarce. This study presents a DFT-FDTD framework to optimize light extraction via compositional tuning and plasmonic enhancement. First, DFT calculations were performed to obtain composition-specific complex refractive index and extinction coefficient values for $x = 0, 0.25, 0.5, 0.75$ , and $1$ . Results show bandgap increased from 1.331 eV for CsSnI $_{3}$ to 1.927 eV for CsGeI $_{3}$ with increasing Ge content, while refractive index ranges from 2.2 to 2.6 across compositions. These optical constants were then used as inputs for FDTD simulations of a PeLED structure with optimized Au/SiO $_{2}$ core-shell nanorods for plasmonic enhancement. A 12.1-fold Purcell enhancement was achieved for CsSn $_{0.25}$ Ge $_{0.75}$ I $_{3}$ , while light extraction efficiency reached 25% for CsSn $_{0.5}$ Ge $_{0.5}$ I $_{3}$ . LEE enhancement of 36% was obtained for CsSnI $_{3}$ , and spectral overlap between emitter and plasmon resonance reached 96% for Sn-rich compositions. Design guidelines indicate CsSn $_{0.5}$ Ge $_{0.5}$ I $_{3}$ offers optimal balance of extraction efficiency (25%), Purcell enhancement (5.3 $\times$ ), spectral overlap (93%), and oxidation stability for wearable and flexible optoelectronic applications, while CsSn $_{0.25}$ Ge $_{0.75}$ I $_{3}$ is recommended for applications prioritizing spontaneous emission rate.

An Integrated DFT-FDTD Design of Plasmon-Enhanced Lead-Free CsSnx​Ge1−x​I3​ Perovskite LEDs

Abstract

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An Integrated DFT-FDTD Design of Plasmon-Enhanced Lead-Free $C s S n$ $_{x}$ $G e$ $_{1 - x}$ $I$ $_{3}$ Perovskite LEDs