Phenylquinoline derivatives as efficient interfacial layer materials for high-performance organic electronic devices

Thin film electronic and optoelectronic devices demand electrodes with a work function (Φ) that is sufficiently low to facilitate the transport of electrons in and out of the lowest unoccupied molecular orbital of a given semiconductor. Herein, phenothiazine-, carbazole-, and fluorene-based phenylquinoline derivatives as efficient interfacial layer (IL) materials for solution-processable organic and metal oxide electronic devices are reported. The IL is applied on top of a charge injection electrode in various solution-processed devices, including n-channel organic thin-film transistors (OTFTs) with [6,6]-phenyl C₇₁-butyric acid methyl ester (PC₇₁BM) and poly[N,N′-bis(2-octyldodecyl)-naphthalene-1,4:5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene) [P(NDI2OD-T2)] and amorphous indium gallium zinc oxide (IGZO) transistors, and also in organic photovoltaics (OPVs). Both PC₇₁BM- and P(NDI2OD-T2)-based n-channel OTFTs with IL show enhanced mobility by more than 200% compared to bare Au electrode. IGZO transistors showed much improved mobility of 15.3 cm² V⁻¹ s⁻¹ with an IL compared to bare Au (0.6 cm² V⁻¹ s⁻¹) device. A significantly improved power conversion efficiency (PCE) of 7.63% is obtained for IL utilizing the poly[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]-thiophenediyl] (PTB7):PC₇₁BM based OPVs compared to 4.75% of control device. Ultraviolet photoelectron spectroscopy study reveals that phenylquinoline derivatives significantly lower the Φ of Au, thus facilitating electron injection/extraction in the device.