Organic-2D Material Heterostructures: A Promising Platform for Exciton Condensation and Multiplication

Abstract

We predict that high temperature Bose−Einstein condensation of charge transfer excitons can be achieved in organic-two-dimensional (2D) material heterostructures, at ∼50− 100 K. Unlike 2D bilayers that can be angle-misaligned, organic-2D systems generally have momentum-direct low-energy excitons, thus favoring condensation. Our predictions are obtained for ZnPc−MoS 2 using state-of-the-art first-principles calculations with the GW-BSE approach. The exciton energies we predict are in excellent agreement with recent experiments. The lowest energy charge transfer excitons in ZnPc−MoS 2 are strongly bound with a spatial extent of ∼1−2 nm and long lifetimes (τ 0 ∼ 1 ns), making them ideal for exciton condensation. We also predict the emergence of inter-ZnPc excitons that are stabilized by the interaction of the molecules with the 2D substrate. This novel way of stabilizing intermolecular excitons by indirect substrate mediation suggests design strategies for singlet fission and exciton multiplication, which are important to overcome the Shockley-Queisser efficiency limit in solar cells.

Twisting Enabled Charge Transfer Excitons in Epitaxially Fused Quantum Dot Molecules

“…Figure b). This large exciton size is comparable to the recently reported CT exciton size (∼10–20 Å) realized in the organic-2D material heterostructures, therefore making the excitons ideal for exciton condensation. We find that the dimer molecule exhibits the same dimerization energies at different twisted angles (θ = 30° and 60°) and therefore equal stability (cf.…”

Tuning moiré excitons in Janus heterobilayers for high-temperature Bose-Einstein condensation

“…The critical Mott density n c can be determined by the exciton Bohr radius R via nc≈1normalπR2 ( 15 , 17 , 29 , 30 ). Here, we estimate the exciton Bohr radius R by the root mean square (RMS) radius of the exciton wave function defined as ( 17 )R2=normal〈RMSnormal〉=∫∣r−r0∣2normalρfalse(rfalse)italicdr∫normalρfalse(rfalse)italicdr…”

Two‐dimensional Transition metal Dichalcogenides as an Emerging Platform for Singlet Fission Solar Cells

“…revealed that singlet energy transfer from tetracene to WSe 2 occurred in 3 ps, followed by hole transfer contrariwise in 16.5 ps (Figure 6c) [48] . The rapid charge or energy transfer observed in aforementioned heterostructures is a result of a strong intermolecular electronic coupling or hybridization between organic and TMD semiconductors [49] …”

“…[48] The rapid charge or energy transfer observed in aforementioned heterostructures is a result of a strong intermolecular electronic coupling or hybridization between organic and TMD semiconductors. [49] Researchers have recently exploited TMDs as viable inorganic counterparts for populating the triplet exciton states of organic semiconductors. For example, Kafle et al studied MoS 2 as a triplet sensitizer for zinc phthalocyanine (ZnPc).…”