Trap-Filling Magnetoconductance as an Initialization and Readout Mechanism of Triplet Exciton Spins

Abstract

Photoexcited triplet states are promising candidates for hybrid qubit systems, as they can be used as a controlling gate for nuclear spins. But microwave readout schemes do not generally offer the sensitivity needed to approach the single-molecule limit or the scope to integrate such systems into devices. Here, we demonstrate the possibility of electrical readout of triplet spins at room temperature through a specific mechanism of magnetoconductance (MC) in polycrystalline pentacene. We show that hole-only pentacene devices exhibit a positive photoinduced MC response that is consistent with a trap-filling mechanism. Spin and magnetic-field-dependent quenching of photogenerated triplets by holes quantitatively explains the MC response we observe. These results are distinct in both sign and proposed mechanism compared to previous reports on polyacene materials and provide clear design rules for future spintronic devices based on this spin-sensing mechanism.

Charge Concentration Limits the Hydrogen Evolution Rate in Organic Nanoparticle Photocatalysts

“…The model we use, referred to here as the exciton-carrier annihilation (ECA) model, is described in Equation ( 1) and ( 2 been shown to describe the kinetics of other common organic semiconductors. [34][35][36][37][38][39] d…”

Molecular Control of Triplet-Pair Spin Polarization and Its Optoelectronic Magnetic Resonance Probes

“…Both of these possible outcomes (quenching and scattering) might influence current in their own way. Our work has shown that such behavior dominates the magnetoconductance behavior of bulk pentacene devices, making it a potentially useful mechanism for the readout and control of triplet excitons …”

“…The key result is shown in Figure c, giving the magnetoconductance curves in the light (red) and dark (black) regions, which were fit using our quantum kinetic model. The quartet character of the triplet–doublet encounter complex is calculated via the stochastic Liouville equation (SLE), and the magnetoconductance is modeled by solving a system of kinetic equations at steady-state with the SLE populations as an input parameter . We invoke a trap filling mechanism to explain this counterintuitive increase in conductance with the magnetic field, illustrated in Figure a,b.…”

“…Our work has shown that such behavior dominates the magnetoconductance behavior of bulk pentacene devices, making it a potentially useful mechanism for the readout and control of triplet excitons. 24 …”

“…There are at least four photochemical pathways toward the vision articulated above: photoinitiated radical ion pairs, ,,, ligand-field state engineering, photoexcited triplets derived from intersystem crossing, , and singlet fission (SF). − ,,− Our work has focused on the last of these pathways due to its unique and potentially powerful properties, including ultrafast (sub-nanosecond) state preparation, the possibility of controlling spin evolution through both the inter- and intramolecular structure, and the demonstrated optical and electrical pathways toward ultrasensitive spin readout.…”