Light Emission in 2D Silver Phenylchalcogenolates

Abstract

Silver phenylselenolate (AgSePh, also known as “mithrene”) and silver phenyltellurolate (AgTePh, also known as “tethrene”) are two-dimensional (2D) van der Waals semiconductors belonging to an emerging class of hybrid organic–inorganic materials called metal–organic chalcogenolates. Despite having the same crystal structure, AgSePh and AgTePh exhibit a strikingly different excitonic behavior. Whereas AgSePh exhibits narrow, fast luminescence with a minimal Stokes shift, AgTePh exhibits comparatively slow luminescence that is significantly broadened and red-shifted from its absorption minimum. Using time-resolved and temperature-dependent absorption and emission microspectroscopy, combined with subgap photoexcitation studies, we show that exciton dynamics in AgTePh films are dominated by an intrinsic self-trapping behavior, whereas dynamics in AgSePh films are dominated by the interaction of band-edge excitons with a finite number of extrinsic defect/trap states. Density functional theory calculations reveal that AgSePh has simple parabolic band edges with a direct gap at Γ, whereas AgTePh has a saddle point at Γ with a horizontal splitting along the Γ-N1 direction. The correlation between the unique band structure of AgTePh and exciton self-trapping behavior is unclear, prompting further exploration of excitonic phenomena in this emerging class of hybrid 2D semiconductors.

1D Hybrid Semiconductor Silver 2,6-Difluorophenylselenolate

“…Dimensional reduction of organic–inorganic hybrid semiconductors affords dynamic changes in optical, electronic, and vibrational properties . For example, transformation of bulk three-dimensional (3D) halide perovskites into two- (2D), one- (1D), or zero-dimensional (0D) perovskite structures through the modification of organic cations leads to increases in the electronic band gap and exciton binding energy through quantum and dielectric confinement effects. − Metal–organic chalcogenolates (MOCs) are another emerging family of low-dimensional hybrid materials, , finding applications as light emitters, − field-effect transistors, , photoconductors, ,− photonic reflectors, and sensors . MOCs are distinguished from other low-dimensional semiconductors such as halide perovskites and transition metal chalcogenides by the covalent interaction between metals and organic ligands.…”

Dimensionality Engineering of Lead Organic Chalcogenide Semiconductors

“…In addition, the indirect band gaps of LOCs likely caused the prevalence of STE emission over the band edge emission. For example, in terms of the Ag-based MOCs, the PL of AgSePh, which exhibits a direct band gap, is dominated by the free excitons, while a recent report on AgTePh, which has an indirect band gap, was characterized as a barrier-less STE emission with a trapping energy around 50 meV …”

“…For example, in terms of the Ag-based MOCs, the PL of AgSePh, which exhibits a direct band gap, is dominated by the free excitons, while a recent report on AgTePh, which has an indirect band gap, was characterized as a barrier-less STE emission with a trapping energy around 50 meV. 48 Furthermore, we demonstrated the viability of LOCs in optoelectronic devices by the fabrication of a prototypical single crystal photodetector. Exfoliated single crystals were drytransferred to prepatterned gold electrodes with a gap of 3 μm (Figure 5a,c).…”

Controlled Assembly of CdSe Nanoplatelet Thin Films and Nanowires

“…This type of architecture is ideal for 2D materials where charges travel freely in the plane of conduction. Traditional fabrication methods for these 2D materials employ slow and expensive techniques such as molecular beam epitaxy, atomic layer, or chemical vapor depositions, discouraging large-scale utilization. , Recently, this scenario has dramatically shifted with the development of efficient and inexpensive routes for the synthesis of transition-metal dichalcogenide monolayers − and semiconductor nanoplatelets (NPs). − …”