Organic light-emitting diode(OLED)is an electroluminescent technology that relies on charge-carrier dynamics and is a potential light source for variable environmental conditions.Here,by exploiting a self-developed lo...Organic light-emitting diode(OLED)is an electroluminescent technology that relies on charge-carrier dynamics and is a potential light source for variable environmental conditions.Here,by exploiting a self-developed low-temperature testing system,we investigated the characteristics of hole/electron transport,electro-optic conversion efficiency,and operation lifetime of OLEDs at low-temperature ranging from-40℃to 0℃and room temperature(25℃).Compared to devices operating at room temperature,the carrier transport capability is significantly decreased with reducing temperature,and especially the mobility of the hole-transporting material(HTM)and electron-transporting material(ETM)at-40℃decreases from 1.16×10-6 cm2/V·s and 2.60×10-4 cm2/V·s to 6.91×10-9 cm2/V·s and 1.44×10-5 cm2/V·s,respectively.Indeed,the temperature affects differently on the mobilities of HTM and ETM,which favors unbalanced charge-carrier transport and recombination in OLEDs,thereby leading to the maximum current efficiency decreased from 6.46 cd·A-1 at 25℃to 2.74 cd·A-1 at-40℃.In addition,blue fluorescent OLED at-20℃has an above 56%lifetime improvement(time to 80%of the initial luminance)over the reference device at room temperature,which is attributed to efficiently dissipating heat generated inside the device by the low-temperature environment.展开更多
Due to the high decay rate of the non-radiative transition of long wavelengths, the molecular design of efficient and stable near-infrared(NIR) electroluminescent materials remains a big challenge. Herein,a new tetrad...Due to the high decay rate of the non-radiative transition of long wavelengths, the molecular design of efficient and stable near-infrared(NIR) electroluminescent materials remains a big challenge. Herein,a new tetradentate cyclometalated platinum(II) complex with an N∧C∧C∧N coordinated framework has been developed and used as a dopant for NIR organic light-emitting diodes(OLEDs). The complex exhibited a short-lived(0.5–1.5 μs) metal-to-ligand charge transfer(MLCT) excited state in doped and neat films. The resulting NIR OLEDs(λ_(EL)= 730 nm) achieved maximum external quantum efficiency(EQE_(max))of 5.2% and radiance of 74626 m W sr^(-1)m^(–2). Of note, the device exhibited excellent stability with operational lifetime of 119 h for LT_(90). This work demonstrated the great potential of tetradentate platinum(II)complexes in the field of NIR OLEDs.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61775130 and 11974236)the Science and Technology Commission of Shanghai Municipality Program,China(Grant Nos.19DZ2281000 and 17DZ2281000)the Research Innovation Program for College Graduates of Jiangsu Province,China(Grant Nos.KYCX202545 and KYCX202549)。
文摘Organic light-emitting diode(OLED)is an electroluminescent technology that relies on charge-carrier dynamics and is a potential light source for variable environmental conditions.Here,by exploiting a self-developed low-temperature testing system,we investigated the characteristics of hole/electron transport,electro-optic conversion efficiency,and operation lifetime of OLEDs at low-temperature ranging from-40℃to 0℃and room temperature(25℃).Compared to devices operating at room temperature,the carrier transport capability is significantly decreased with reducing temperature,and especially the mobility of the hole-transporting material(HTM)and electron-transporting material(ETM)at-40℃decreases from 1.16×10-6 cm2/V·s and 2.60×10-4 cm2/V·s to 6.91×10-9 cm2/V·s and 1.44×10-5 cm2/V·s,respectively.Indeed,the temperature affects differently on the mobilities of HTM and ETM,which favors unbalanced charge-carrier transport and recombination in OLEDs,thereby leading to the maximum current efficiency decreased from 6.46 cd·A-1 at 25℃to 2.74 cd·A-1 at-40℃.In addition,blue fluorescent OLED at-20℃has an above 56%lifetime improvement(time to 80%of the initial luminance)over the reference device at room temperature,which is attributed to efficiently dissipating heat generated inside the device by the low-temperature environment.
基金financially supported by the National Natural Science Foundation of China (Nos. 51903157 and 52130308)the Shenzhen Science and Technology Program (Nos. KQTD20170330110107046 and ZDSYS20210623091813040)the School of Materials Science and Engineering, Jiangsu Engineering Laboratory of Light-Electricity-Heat Energy-Converting Materials and Applications (No. GDRGCS2021001)。
文摘Due to the high decay rate of the non-radiative transition of long wavelengths, the molecular design of efficient and stable near-infrared(NIR) electroluminescent materials remains a big challenge. Herein,a new tetradentate cyclometalated platinum(II) complex with an N∧C∧C∧N coordinated framework has been developed and used as a dopant for NIR organic light-emitting diodes(OLEDs). The complex exhibited a short-lived(0.5–1.5 μs) metal-to-ligand charge transfer(MLCT) excited state in doped and neat films. The resulting NIR OLEDs(λ_(EL)= 730 nm) achieved maximum external quantum efficiency(EQE_(max))of 5.2% and radiance of 74626 m W sr^(-1)m^(–2). Of note, the device exhibited excellent stability with operational lifetime of 119 h for LT_(90). This work demonstrated the great potential of tetradentate platinum(II)complexes in the field of NIR OLEDs.
