Publication date: 17th July 2025
The performance and stability of the perovskite nanocrystal light-emitting diodes (PeNCs-LEDs) are critically influenced by the selection of the hole transporting material (HTM), which plays a pivotal role in facilitating efficient charge injection and balancing carrier transport. A conventional polymer-based HTM, such as PEDOT: PSS, often suffers from limitations including poor energy level alignment, and instability under ambient conditions. In this work, we introduce and investigate two small-molecule HTM candidates, 4-(3,6-bis(2,4-dimethoxyphenyl)-9H-carbazol-9-yl) benzoic acid (CP202) and (4-(3,7-di(thiophen-2-yl)-10H-phenothiazin-10-yl) phenyl) phosphonic acid (CP0047), as efficient and robust alternatives to traditional polymers in PeNCs-LEDs architectures. These molecules offer tunable energy levels, strong interfacial bonding to the substrate through phosphonic acid or carboxylic acid anchoring groups, and excellent surface passivation. Their SAM nature ensures minimal layer thickness, leading to possible improved charge injection and reduced interface defects.
Formamidinium lead bromide (FAPbBr3) nanocrystals offer superior optical and electronic properties compared to their cesium-based counterparts, making them excellent candidates for high-performance PeNCs-LEDs. Their enhanced crystallinity, narrow emission linewidth, and high photoluminescence quantum yield result from optimized synthesis that ensures high phase purity and minimal surface defects. The cleaner surface chemistry promotes better energy level alignment and more efficient charge injection when interfaced with SAM-based hole transport layers (HTLs) Additionally, the improved surface passivation reduces non-radiative recombination pathways, leading to increased brightness and operational stability. These qualities collectively enable the fabrication of efficient, solution-processed light-emitting devices.
The synergistic effect between the FAPbBr2 NCs and the SAM-engineered HTLs offer a compelling route toward next-generation optoelectronic devices with improved efficiency and stability.
- This work is partially funded by the Ministerio de Ciencia e Innovación of the Spanish government by the Severo Ochoa Grant MCIU/AEI/10.13039/501100011033 (CEX2024-001469-S); by the project ElectroVolt PID2022-139866NB-I00, and by the project Lemoskites CNS2022-135483-MCIN/AEI/10.13039/501100011033. Financial support from the European Union through the ERC Advanced grant ERC 101097684- Excited is appreciated
- The authors also acknowledge ICIQ, CERCA, and ICREA for financial support
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