Origin of Hole-Trapping States in Solution-Processed Copper(I) Thiocyanate (CuSCN) and Defect-Healing by I2_2 Doping

Solution-processed copper(I) thiocyanate (CuSCN) typically exhibits low crystallinity with short-range order; the defects result in a high density of trap states that limit the device performance. Despite the extensive electronic applications of CuSCN, its defect properties have not been studied in detail. Through X-ray absorption spectroscopy, pristine CuSCN prepared from the standard diethyl sulfide-based recipe is found to contain under-coordinated Cu atoms, pointing to the presence of SCN vacancies. A defect passivation strategy is introduced by adding solid I$_2$ to the processing solution. At small concentrations, the iodine is found to exist as I$^-$ which can substitute for the missing SCN$^-$ ligand, effectively healing the defective sites and restoring the coordination around Cu. Applying I$_2$-doped CuSCN as a p-channel in thin-film transistors shows that the hole mobility increases by more than five times at the optimal doping concentration of 0.5 mol%. Importantly, the on/off current ratio and the subthreshold characteristics also improve as the I$_2$ doping method leads to the defect healing effect while avoiding the creation of detrimental impurity states. An analysis of the capacitance-voltage characteristics corroborates that the trap state density is reduced upon I$_2$ addition. The contact resistance and bias-stress stability of the devices also improve. This work shows a simple and effective route to improve hole transport properties of CuSCN which is applicable to wide-ranging electronic and optoelectronic applications

A highly efficient near infrared organic solid fluorophore based on naphthothiadiazole derivatives with aggregation-induced emission enhancement for a non-doped electroluminescent device

Naphthothiadiazole derivatives with aggregation-induced emission enhancement exhibited a non-doped EL device emitted brilliant near infrared emission peaked at 754 nm with high EQE as high as 1.48%.</p

Chrysene-Cored Fluorescent Dendrimers as Nondoped Deep-Blue Emitters for Solution-Processable Electroluminescent Devices

AbstractNew solution-processable chrysene-basked deep-blue fluorescent dendrimers consisting of chrysene as a core end-capped by carbazole dendrons were designed, synthesized, and characterized. These dendrimers exhibit strong deep-blue emissions in solution or thin-film states with decent hole mobility and high thermal and electrochemical stability. They can be effectively used as nondoped emitters in organic light-emitting diodes (OLEDs). The nondoped OLEDs, which have a simple structure, showed good electroluminescence (EL) performance (luminance: 2334–2400 cd m–2; external quantum efficiency: 1.88-2.51%; turn-on voltage: 3.8–4.0 V) and deep-blue EL spectra (CIE y: 0.065–0.075) with a narrow full width at half maximum of 61–65 nm.</jats:p

Double anchor indolo[3,2-<i>b</i>]indole-derived metal-free dyes with extra electron donors as efficient sensitizers for dye-sensitized solar cells

New di-acceptors organic dye with extra electron donors shows an enhanced PCE of 7.86% comparing to parent one.</p

Antisolvent treatment of copper(<scp>i</scp>) thiocyanate (CuSCN) hole transport layer for efficiency improvements in organic solar cells and light-emitting diodes

A facile antisolvent treatment of CuSCN hole transport layers can be readily applied to improve carrier transport and efficiencies of organic optoelectronic devices.</jats:p