Enhancing Carrier Balance in Blade-Coated Near-Infrared Quantum Dot Light-Emitting Diodes by a PSS-Rich PEDOT:PSS Hole-Buffering Layer.

Perovskite quantum dots (PQDs) have attracted significant attention for near-infrared (NIR) light-emitting diodes (LEDs). However, the device performance is fundamentally limited by charge imbalance and challenges in scalable fabrication. Here, a strategy is reported to simultaneously optimize charge transport and film morphology by employing poly(sodium-4-styrene sulfonate) (PSSNa)-modified poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as a hole-buffering layer (HBL) for blade-coated FAPbI3 PQD-based NIR-LEDs. The addition of PSSNa dilutes the conductive PEDOT network, reducing the conductivity (from ≈1.03 × 10-4 to ≈0.85 × 10-4 S cm-1), and mitigating hole over-injection. Furthermore, the PSSNa-modified PEDOT:PSS exhibits a smoother surface with higher wettability, which facilitates the deposition of subsequent layers. Notably, the PQD layer deposited on the optimized HTL shows significantly improved compactness, with reduced pinhole density, thereby minimizing leakage currents and non-radiative recombination. Consequently, the devices achieve external quantum efficiencies of 22.4% and 18.3% for active areas of 10 mm2 and 625 mm2, respectively, at an emission wavelength of 780 nm. This work highlights a facile strategy to simultaneously optimize charge balance and interfacial morphology for scalable PQD optoelectronics.