In organic solar cells,the singlet and triplet excitons dissociate into free charge carriers with different mechanisms due to their opposite spin state.Therefore,the ratio of the singlet and triplet excitons directly ...In organic solar cells,the singlet and triplet excitons dissociate into free charge carriers with different mechanisms due to their opposite spin state.Therefore,the ratio of the singlet and triplet excitons directly affects the photocurrent.Many methods were used to optimize the performance of the low-efficiency solar cell by improving the ratio of triplet excitons,which shows a long diffusion length.Here we observed that in high-efficiency systems,the proportion of singlet excitons under linearly polarized light excitation is higher than that of circularly polarized light.Since the singlet charge transfer state has lower binding energy than the triplet state,it makes a significant contribution to the charge carrier generation and enhancement of the photocurrent.Further,the positive magnetic field effect reflects that singlet excitons dissociation plays a major role in the photocurrent,which is opposite to the case of low-efficiency devices where triplet excitons dominate the photocurrent.展开更多
The emission manners of organic light-emitting diodes（OLEDs） have experienced almost three-decade evolution.In this review,we briefly summarized the emission manners of OLEDs including：（ⅰ） emission from singlet ...The emission manners of organic light-emitting diodes（OLEDs） have experienced almost three-decade evolution.In this review,we briefly summarized the emission manners of OLEDs including：（ⅰ） emission from singlet exciton;（ⅱ） emission from triplet exciton;（ⅲ） emission from singlet exciton converted from triplet exciton.Then we introduced a new type of OLEDs with the emission from doublet exciton,wherein organic neutral radicals are used as emitters.Due to the spin-allowed transition of doublet excitons,using neutral radicals as emitters is believed to be a new way to break the 25%upper limit of internal quantum efficiency of OLEDs.The progress of emissive stable neutral radicals is also shortly reviewed.展开更多
An efficient color-tunable hybrid white organic light-emitting diode is demonstrated with double interlayers of 2,7-bis(carbazol-9-yl)-9,9-ditoylfluo- rene/2-(diphenylphosphoryl) spiroflu-orene (DMFL-CBP/SPPO1) insert...An efficient color-tunable hybrid white organic light-emitting diode is demonstrated with double interlayers of 2,7-bis(carbazol-9-yl)-9,9-ditoylfluo- rene/2-(diphenylphosphoryl) spiroflu-orene (DMFL-CBP/SPPO1) inserted between blue fluorescent and yellow phosphorescent-emitting layers, and exhibits Commission Internationale de l’Eclairage (CIE1931) ranging from warm white (0.4368, 0.4497) to cool white (0.2781, 0.2896) with driving current density from 0.2 to 40 mA/cm2. The recombination of singlet and the triplet excitons in blue fluores-cent-emitting layer and yellow phosphorescent-emitting layer, respectively, can be modulated by both the thickness of these double interlayers and the applied current densities.展开更多
Tris-（8-hydroxyquinoline）-aluminum eAlq3T–based organic light-emitting diodes with Co electrode are fabricated. The positive magnetic electroluminescence（MEL） and magnetic conductance（MC） are observed in the sa...Tris-（8-hydroxyquinoline）-aluminum eAlq3T–based organic light-emitting diodes with Co electrode are fabricated. The positive magnetic electroluminescence（MEL） and magnetic conductance（MC） are observed in the samples, reaching 4.35% and 1.67% under the field of 42 m T at 50 K, respectively, and the MEL and MC traces can be fitted to non-Lorentzian line shapes. The MEL varies as a function of the Co thickness and reaches the optimal value at 10 nm. The MEL and MC dependence on voltage and temperature is also investigated. The electron-hole pair model and the spin-polarized injection mechanism are used to understand the experimental results.展开更多
基金the National Key Research and Development Program of China(No.2018YFE0204000)the National Natural Science Foundation of China(Nos.U20A20206,51972300,62274155,and 21975245)+3 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB43000000)the Key Research Program of Frontier Science,Chinese Academy of Sciences(No.QYZDBSSWSLH006)K.L.appreciates the support from the Youth Innovation Promotion Association,the Chinese Academy of Sciences(No.2020114)the Beijing Nova Program(No.2020117).
文摘In organic solar cells,the singlet and triplet excitons dissociate into free charge carriers with different mechanisms due to their opposite spin state.Therefore,the ratio of the singlet and triplet excitons directly affects the photocurrent.Many methods were used to optimize the performance of the low-efficiency solar cell by improving the ratio of triplet excitons,which shows a long diffusion length.Here we observed that in high-efficiency systems,the proportion of singlet excitons under linearly polarized light excitation is higher than that of circularly polarized light.Since the singlet charge transfer state has lower binding energy than the triplet state,it makes a significant contribution to the charge carrier generation and enhancement of the photocurrent.Further,the positive magnetic field effect reflects that singlet excitons dissociation plays a major role in the photocurrent,which is opposite to the case of low-efficiency devices where triplet excitons dominate the photocurrent.
基金financial support from the Ministry of Science and Technology of China(No.2015CB655003)National Natural Science Foundation of China(No.61275036)
文摘The emission manners of organic light-emitting diodes（OLEDs） have experienced almost three-decade evolution.In this review,we briefly summarized the emission manners of OLEDs including：（ⅰ） emission from singlet exciton;（ⅱ） emission from triplet exciton;（ⅲ） emission from singlet exciton converted from triplet exciton.Then we introduced a new type of OLEDs with the emission from doublet exciton,wherein organic neutral radicals are used as emitters.Due to the spin-allowed transition of doublet excitons,using neutral radicals as emitters is believed to be a new way to break the 25%upper limit of internal quantum efficiency of OLEDs.The progress of emissive stable neutral radicals is also shortly reviewed.
文摘An efficient color-tunable hybrid white organic light-emitting diode is demonstrated with double interlayers of 2,7-bis(carbazol-9-yl)-9,9-ditoylfluo- rene/2-(diphenylphosphoryl) spiroflu-orene (DMFL-CBP/SPPO1) inserted between blue fluorescent and yellow phosphorescent-emitting layers, and exhibits Commission Internationale de l’Eclairage (CIE1931) ranging from warm white (0.4368, 0.4497) to cool white (0.2781, 0.2896) with driving current density from 0.2 to 40 mA/cm2. The recombination of singlet and the triplet excitons in blue fluores-cent-emitting layer and yellow phosphorescent-emitting layer, respectively, can be modulated by both the thickness of these double interlayers and the applied current densities.
基金supported by the National Natural Science Foundation of China(No.61076093)the Natural Science Foundation of Shanghai(No.14ZR1402900)
文摘Tris-（8-hydroxyquinoline）-aluminum eAlq3T–based organic light-emitting diodes with Co electrode are fabricated. The positive magnetic electroluminescence（MEL） and magnetic conductance（MC） are observed in the samples, reaching 4.35% and 1.67% under the field of 42 m T at 50 K, respectively, and the MEL and MC traces can be fitted to non-Lorentzian line shapes. The MEL varies as a function of the Co thickness and reaches the optimal value at 10 nm. The MEL and MC dependence on voltage and temperature is also investigated. The electron-hole pair model and the spin-polarized injection mechanism are used to understand the experimental results.
