Solution‐Processed and Room‐Temperature Spin Light‐Emitting Diode Based on Quantum Dots/Chiral Metal‐Organic Framework Heterostructure

Abstract

Spin optoelectronics is an indispensable key for the future development of spintronics. In conventional spin light emitting diodes (LEDs), spin‐polarized carrier pairs are injected electrically into the light emitting layer and create circularly polarized light (CPL). Generally, spin‐polarized carriers are accomplished using ferromagnetic contacts or applying an external magnetic field, which will produce several drawbacks, including low temperature operation, low spin‐polarized carriers injection efficiency, etc. To circumvent the existing shortcomings, here, an alternative approach is proposed and achieves spin‐polarized LEDs at room temperature based on quantum dots (QDs)/chiral metal‐organic framework heterojunction without using ferromagnetic contacts or magnetic fields. The spin‐polarized injected layer composed of self‐assembled monolayer (SAM)/Chiral‐MOF ([Sr(9,10‐adc)(DMAc)2]n)) film, which produces spin‐polarized holes with spin orientation, determining the polarization and strength of circularly polarized electroluminescence (CP‐EL). The spin‐QLED emits CP‐EL at a rate of 12.24% efficiency, which provides an excellent alternative to generate new functionality for conventional QLEDs. The approach is anticipated to be very useful, enabling to offer a general methodology for generating not yet realized spin optoelectronic devices.

Chiral Induced Spin Selectivity

“…In other work, Mustaqeem et al used chiral metal–organic frameworks as the spin injection layer and an impressive P CP‑EL was observed at ZnS­(CdSe) core–shell recombination sites; ca. 12.4% at room temperature . The large P CP‑EL was attributed to enhanced spin-coherence lifetime of the charge carriers.…”

“…12.4% at room temperature. 312 The large P CP-EL was attributed to enhanced spin-coherence lifetime of the charge carriers.…”

Spin-polarized white organic light-emitting diodes based on chirality-induced spin selectivity effect

“…Based on CISS effect, CP-EL can be realized in spin-polarized light-emitting diodes (spin-LEDs), in which spin-polarized electrons (or holes) are recombined with unpolarized holes (or electrons) to form spin-polarized carrier pairs, namely spin-polarized excitons 45,46 . However, the reported CISS effect driven room temperature spin-LEDs rely on the chiral metal-halide perovskite hybrid semiconductor to generate spin-polarized charge carriers, which make the color modulation of CP-EL difficult [47][48][49] , let alone achieving white CP-EL in a single spin-LED device. Recently, some organic chiral materials are demonstrated to have CISS effect at room temperature [50][51][52] , which inspires us to harness CISS effect to acquire spin-polarized charge carriers for the construction of spin-polarized OLEDs (spin-OLEDs) with organic chiral materials.…”

Dimensional and Doping Engineering of Chiral Perovskites with Enhanced Spin Selectivity for Green Emissive Spin Light-Emitting Diodes

“…The performance of the obtained spin-LEDs stands out among previous reports (Table S2). Furthermore, we conducted a rough estimation of the degree of polarization for the spin-LEDs, which can be obtained by calculating the ratio of spin relaxation time to carrier lifetime (τ spin /τ carrier ) within the emissive layer. , We conducted an ultrafast transient absorption (TA) measurement and obtained a τ spin of 6.6 ps from the fitting curve of spin-coherence dynamics for CsPbBr 3 PeNCs (Figures S18 and S19). Additionally, the τ carrier values reflected by the photoluminescent lifetime decay curve of (PEA) x (S-PRDA) 2– x Sn 0.1 Pb 0.9 Br 4 /CsPbBr 3 PeNCs/PO-T2T-laminated films were detected to be 4.75 ns (Figure S20).…”

“…Due to optical selection rules, the spin multiplicity of excitons is maintained during radiative recombination, thus emitting spin-polarized photons. Consequently, the emission of left/right-handed light (σ – /σ + ) becomes achievable when the population of the spin state (↑/↓) is polarized during the recombination process without any ferromagnetic layers and external magnetic fields. − …”