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Adlayers are often placed at metal-on-organic interfaces as a common strategy to alleviate damage during metal deposition by thermal evaporation. Methods of chemically installing adlayers have been recently demonstrated on organic semiconductors that address these interfacial issues while providing many secondary benefits. Chemical installation has yet to be attempted at the cathode-electron transport layer (ETL) interface within organic light-emitting devices (OLEDs), offering a powerful option to optimize electron injection, improve surface wetting, and reduce metal penetration. Here, a reaction between TPBi (2,2′,2′’-(1,2,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) and propylene oxide results in a controllable 1–3 nm thick layer of propylene oxide as shown by high-resolution X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX). The reactive addition of the adlayer at temperatures below 40℃ does not affect the morphology of the thin film and reaches a high degree of coverage within 3 h. Integration of this layer into a phosphorescent OLED does not introduce any significant negative impact on device function. This result opens up the possibility of introducing further specific functionality into the adlayer to engineer OLED performance. 

Photovoltaic cells based on metal‐halide perovskites have exceeded the performance of other thin film technologies and rival the performance of devices based on archetypical silicon. Attractively, the perovskite active layer can be processed via a variety of solution‐ and vapor‐based methods. Herein, emphasis is on the use of vapor transport codeposition (VTD) to process efficient n–i–p photovoltaic cells based on methylammonium lead iodide (MAPbI₃). VTD utilizes a hot‐walled reactor operated under moderate vacuum in the range of 0.5–10 Torr. The organic and metal‐halide precursors are heated with the resulting vapor transported by a N₂carrier gas to a cooled substrate where they condense and react to form a perovskite film. The efficiency of photovoltaic devices based on VTD‐processed MAPbI₃is found to be highest in films with excess lead iodide content, with champion devices realizing exceeding 12%. 

We demonstrate the impact of subtle changes in molecular structure on the singlet and triplet exciton diffusion lengths ( L D ) for derivatives of the archetypical electron-transport material 4,7-diphenyl-1,10-phenanthroline (BPhen). Specifically, this work offers a systematic characterization of singlet and triplet exciton transport in identically prepared thin films, highlighting the differing dependence on molecular photophysics and intermolecular spacing. For luminescent singlet excitons, photoluminescence quenching measurements yield an L D from <1 nm for BPhen, increasing to (5.4 ± 1.2) nm for 2,9-dichloro-4,7-diphenyl-1,10-phenanthroline (BPhen-Cl 2 ) and (3.9 ± 1.1) nm for 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP). The diffusion of dark triplet excitons is probed using a phosphorescent sensitizer-based method where triplets are selectively injected into the material of interest, with those migrating through the material detected via energy transfer to an adjacent, phosphorescent sensitizer. Interestingly, the triplet exciton L D decreases from (15.4 ± 0.4) nm for BPhen to (8.0 ± 0.7) nm for BPhen-Cl 2 and (4.0 ± 0.5) nm for BCP. The stark difference in behavior observed for singlets and triplets with functionalization is explicitly understood using long-range Förster and short-range Dexter energy transfer mechanisms, respectively.