Lead-free halide double-perovskite quantum dots (QDs) with self-trapped exciton emission offer an environmentally benign platform for broadband and single-phase white-light generation. However, their practical implementation in light-emitting diodes (LEDs) remains limited by modest photoluminescence quantum yields (PLQYs), intrinsic restrictions associated with their indirect bandgap and parity-forbidden transitions, and severe charge losses arising from trap-mediated recombination and inefficient carrier transport. To address these challenges, we develop Sb³⁺/Mn²⁺ co-doped Cs₂NaInCl₆ QD inks combined with short-chain ligand engineering to simultaneously enhance their optical performance, electronic conductivity, and device compatibility [1].

The dual-ion doping strategy provides stable white emission while effectively reducing cation disorder in the perovskite lattice, yielding near-unity PLQY. Meanwhile, replacing conventional long-chain surface ligands with short-chain 2-ethylhexanoic acid and 3,3-diphenylpropylamine chloride dramatically improves charge transport in the QD films. This ligand shortening enhances conductivity by nearly twentyfold, suppresses nonradiative surface recombination, and induces favorable energy-level alignment with the poly(9-vinylcarbazole):poly hole-transport layer, thereby reducing the hole-injection barrier by approximately 0.4 eV. As a result, charge balance in the LED architecture is significantly improved, enabling efficient carrier recombination under electrical excitation.

These combined advances lead to markedly enhanced electroluminescent performance. The resulting LEDs achieve an external quantum efficiency of 0.91% (0.05 cm²), representing the highest reported efficiency for double-perovskite QD-based devices and a 1.3-fold improvement over the previous state-of-the-art. Furthermore, temperature-dependent photoluminescence measurements reveal that increasing temperature drives the gradual fusion of dual-emission bands, enabling a controllable transition from cool white to warmer pure-white emission. This tunable thermal response highlights the potential of these materials for adaptive or color-variable lighting.

Overall, the integration of controlled doping, defect suppression, and short-chain ligand engineering establishes a viable pathway to overcome the intrinsic limitations of lead-free double-perovskite QDs. These findings advance their prospects for high-quality, stable, and environmentally responsible solid-state lighting technologies.