High‐Temperature Single‐Photon Emission From Covalently Functionalized van der Waals Heterostructures

Covalent diazonium functionalization of graphite‐WSe2 heterostructures produces high‐purity single‐photon emission from WSe2 at T = 90 K, far above the typical T = 10 K limit. The chemical modification reshapes graphite's electronic structure and couples to WSe2 midgap states, stabilizing quantum emitters at elevated temperatures and opening pathways toward practical, thermally robust 2D single‐photon devices. Abstract Two‐dimensional (2D) transition metal dichalcogenides (TMDs) such as tungsten diselenide (WSe2) are attractive nanomaterials for quantum information applications due to single‐photon emission (SPE) from intrinsic atomic defects. Defect and strain engineering techniques have been developed to produce high purity, deterministically placed SPE in WSe2. However, a major challenge in the application of these techniques is the low temperature required to observe defect‐bound TMD exciton emission, typically limiting SPE to T < 30 K. SPE at higher temperatures either loses purity or requires integration into complex devices such as optical cavities. Here, 2D heterostructure engineering and molecular functionalization are combined to achieve high purity (>90%) SPE in strained WSe2 persisting to over T = 90 K. Covalent diazonium functionalization of graphite in layered WSe2/graphite heterostructures maintains high purity up to T = 90 K and single‐photon source integrity up to T = 115 K. This method preserves the best qualities of SPE from WSe2 while increasing working temperature to more than three times the typical range. This work demonstrates the versatility of surface functionalization and heterostructure design to synergistically improve the properties of quantum emission and offers new insights into the phenomenon of SPE from 2D materials. Covalent diazonium functionalization of graphite-WSe 2 heterostructures produces high-purity single-photon emission from WSe 2 at T = 90 K, far above the typical T = 10 K limit. The chemical modification reshapes graphite's electronic structure and couples to WSe 2 midgap states, stabilizing quantum emitters at elevated temperatures and opening pathways toward practical, thermally robust 2D single-photon devices. Abstract Two-dimensional (2D) transition metal dichalcogenides (TMDs) such as tungsten diselenide (WSe 2 ) are attractive nanomaterials for quantum information applications due to single-photon emission (SPE) from intrinsic atomic defects. Defect and strain engineering techniques have been developed to produce high purity, deterministically placed SPE in WSe 2. However, a major challenge in the application of these techniques is the low temperature required to observe defect-bound TMD exciton emission, typically limiting SPE to T < 30 K. SPE at higher temperatures either loses purity or requires integration into complex devices such as optical cavities. Here, 2D heterostructure engineering and molecular functionalization are combined to achieve high purity (>90%) SPE in strained WSe 2 persisting to over T = 90 K. Covalent diazonium functionalization of graphite in layered WSe 2 /graphite heterostructures maintains high purity up to T = 90 K and single-photon source integrity up to T = 115 K. This method preserves the best qualities of SPE from WSe 2 while increasing working temperature to more than three times the typical range. This work demonstrates the versatility of surface functionalization and heterostructure design to synergistically improve the properties of quantum emission and offers new insights into the phenomenon of SPE from 2D materials. Advanced Science, Volume 12, Issue 48, December 29, 2025.