Enhanced Circularly Polarized Electroluminescence from Polymer Spin-LEDs via Halogenated Chiral Perovskite Interlayers

Circularly polarized light-emitting diodes based on spin-polarized carrier injection offer a promising route toward spin-encoded optical communication and display technologies. Here, we demonstrate polymer spin-light-emitting diodes employing halogenated thiophene-based chiral perovskites as spin-selective hole-transport interlayers. The devices were fabricated with an ITO/modified-PEDOT:PSS/chiral perovskite/F8BT/TPBi/LiF/Al architecture, in which the achiral conjugated polymer F8BT served as the green-emitting layer. The chiral perovskite interlayers provided energetically favorable hole transport while selectively transmitting carriers according to their spin orientation. Devices incorporating Cl-, Br- and I-substituted chiral ligands exhibited green electroluminescence centered at 540 nm and clear circular polarization, whereas the non-halogenated analogue showed no detectable emission because of its unfavorable film morphology. Both the external quantum efficiency and electroluminescence dissymmetry factor increased systematically with halogen size, reaching a maximum |gEL| of 0.016 for the iodine-substituted perovskite. Circularly polarized photoluminescence was not detected from the F8BT layer alone, and reversal of the emission-detection direction inverted the sign of gEL, confirming that the polarized electroluminescence originates from spin-selective carrier injection rather than intrinsic emitter chirality or passive optical filtering. These results establish halogenated chiral perovskites as tunable spin-selective interlayers for circularly polarized polymer light-emitting diodes.