Indolocarbazole-Based Small Molecule Cathode-Active Material Exhibiting Double Redox for High-Voltage Li-Organic Batteries

Most organic electrode materials(OEMs)for rechargeable batteries employ n-type redox centers,whose redox potentials are intrinsically limited<3.0 V versus Li^(+)/Li.However,p-type materials possessing high redox potentials experience low specific capacities because they are capable of only a single redox reaction within the stable electrochemical window of typical electrolytes.Herein,we report 5,11-diethyl-5,11-dihydroindolo[3,2-b]carbazole(DEICZ)as a novel p-type OEM,exhibiting stable plateaus at high discharge potentials of 3.44 and 4.09 V versus Li^(+)/Li.Notably,the second redox potential of DEICZ is within the stable electrochemical window.The mechanism of the double redox reaction is investigated using both theoretical calculations and experimental measurements,including density functional theory calculations,ex situ electron spin resonance,and X-ray photoelectron spectroscopy.Finally,hybridization with single-walled carbon nanotubes(SWCNT)improves the cycle stability and rate performance of DEICZ owing to theπ-πinteractions between the SWCNT and co-planar molecular structure of DEICZ,preventing the dissolution of active materials into the electrolyte.The DEICZ/SWCNT composite electrode maintains 70.4%of its initial specific capacity at 1-C rate and also exhibits high-rate capability,even performing well at 100-C rate.Furthermore,we demonstrate its potential for flexible batteries after applying 1000 bending stresses to the composite electrode.

Synthesis and Characterization of Polyimides Based on Twisted Non-coplanar Backbone Containing Indolocarbazole

A diamine monomer(4,4’-(((5,11-dihydroindolo[3,2-b]carbazole-6,12-diyl)bis(4,l-phenyl-ene))bis(oxy))dianiline)containing a rigid conjugated indolocarbazole was designed and synthesized through a three-step reaction.A series of high-performance functional polyimides were prepared through simple condensation polymerization of the monomer with different industrial dianhydrides 6FDA,BTDA and ODPA,respectively,which exhibit superior thermal stability,good solubility in polar organic solvents and good mechanical properties.The glass transition temperature(T_(g))is above 334℃,and the 5%weight loss temperature(T_(d5%))of polyimides under nitrogen atmosphere falls in the range of 502〜526℃.The tensile strength and tensile modulus are 49.45~60.08 MPa and 1.4-1.6 GPa,respectively.In addition,the maximum fluorescence emission wavelength of polyimides in the NMP solution(0.02 mg/mL)are around 448 nm with blue light emission and 451 nm as film without significant red shift,which indicates the prepared polyimides process a certain application potential in high-performance flexible polymer optoelectronic devices.

Indolo[3,2,1-jk]carbazole-derived planar electron transport materials realizing high efficiency in green phosphorescent organic light-emitting diodes

Two novel electron transporting materials(ETMs),2-(4,6-diphenyl-1,3,5-triazin-2-yl)indolo[3,2,1-jk]-carbazole(DPTrz-ICz)and 5,11-bis(4,6-diphenyl-1,3,5-triazin-2-yl)-2-phenylindolo[3,2,1-jk]carbazole(2DPTrz-ICz),were developed based on the indolo[3,2,1-jk]carbazole(ICz)core,combined with 2,4-diphenyl-1,3,5-triazine(DPTrz).The introduced ICz core in ETM exhibited enhanced intermolecular charge transport properties owing to its planar and rigid geometry and high triplet energy,demonstrating the potential of designing ETM.Consequently,2DPTrz-ICz,featuring high triplet energy of 2.84 eV,effectively prevented triplet exciton quenching and showed increased electron mobility owing to the activation of intermolecular hopping charge transfer facilitated by stacking architecture.The two materials were utilized as ETMs in green phosphorescent organic light-emitting diodes.2DPTrz-ICz exhibited a superior external quantum efficiency of 21.5%,higher than that of the spirobifluorene-derived ETM.

Highly Efficient and Stable Blue OLEDs Based on B-N Bonds Embedded 6,12-Diphenyl-5,11-dihydroindolo[3,2-b]carbazole with Narrowband Emission and Extended Lifetime

Emitters with narrowband spectra are of great importance nowadays because of the growing demand for ultra-high-definition displays in the fields of panel displays and solid-state lighting.Though the reported multiple resonance(MR)emitters have been widely studied with extremely sharp spectra and color-tunable emissions,the electrophilic borylation synthetic strategies and stable narrowband blue devices still face great challenges.