Abstract
Significant aggregation between ZnO nanoparticles (ZnO NPs) dispersed in polar and nonpolar solvents hinders the formation of high quality thin film for the device application and impedes their excellent electron transporting ability. Herein a bifunctional coordination complex, titanium diisopropoxide bis(acetylacetonate) (Ti(acac)2) is employed as efficient stabilizer to improve colloidal stability of ZnO NPs. Acetylacetonate functionalized ZnO exhibited long-term stability and maintained its superior optical and electrical properties for months aging under ambient atmospheric condition. The functionalized ZnO NPs were then incorporated into polymer solar cells with conventional structure as n-type buffer layer. The devices exhibited nearly identical power conversion efficiency regardless of the use of fresh and old (2 months aged) NPs. Our approach provides a simple and efficient route to boost colloidal stability of ZnO NPs in both polar and nonpolar solvents, which could enable structure-independent intense studies for efficient organic and hybrid optoelectronic devices.
Highlights
ZnO is known as a multifunctional material, which possesses high electrical c onductivity[1] and visible transparency, photostability[2,3], and photocatalytic ability[4,5]
Based on the previous studies, it is expected that ZnO nanoparticles (ZnO NPs) in methanol would possess the advantages of both materials; methanol reconstructs the molecular packing of the active layer toward better morphology and ZnO NPs act as an efficient electron transport layer in the device
Each functionalized ZnO NP solution is denoted as functionalized ZnO NPs (fZnOs)-L, fZnO-M, and fZnO-H, respectively
Summary
ZnO is known as a multifunctional material, which possesses high electrical c onductivity[1] and visible transparency (optical band gap, Eopt > 3.3 eV), photostability[2,3], and photocatalytic ability[4,5] It has been often utilized as a highly efficient n-type buffer layer of organic optoelectronic devices due to its proper energy level alignment to the active layer with ideal band d ispersion[6] for the selective charge extraction (or injection). Despite of the prescribed advantages, poor colloidal stability of ZnO NPs in methanol frustrates their applications in the organic optoelectronics with conventional structure and comprehensive studies on improving colloidal stability of ZnO NPs in methanol solvent have been hardly studied so far. The results provide simple and efficient routes to improve colloidal stability of metal oxide nanoparticles and extend their applications to a variety of device structures of organic optoelectronic devices
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