Extraordinarily High Efficiency Improvement for OLEDs with High Surface-Charge Polymeric Nanodots

Abstract

The efficiency of highly efficient blue, green, red, and white organic light-emitting diodes (OLEDs) has been substantially advanced through the use of high surface-charge nanodots embedded in a nonemissive layer. For example, the blue OLED's markedly high initial power efficiency of 18.0 lm W(-1) at 100 cd m(-2) was doubled to 35.8 lm W(-1) when an amino-functionalized polymeric nanodot was employed. At high luminance, such as 1000 cd m(-2) used for illumination applications, the efficiency was improved from 12.4 to 21.2 lm W(-1), showing a significant enhancement of 71%. The incorporated highly charged nanodots are capable of effectively modulating the transportation of holes via a blocking or trapping mechanism, preventing excessive holes from entering the emissive layer and the resulting carrier-injection imbalance. Furthermore, in the presence of a high-repelling or dragging field arising from the highly charged nanodots, only those holes with sufficient energy are able to overcome the included barriers, causing them to penetrate deeper into the emissive layer. This penetration leads to carrier recombination over a wider region and results in a brighter emission and, therefore, higher efficiency.

Using light-emitting dyes as a co-host to markedly improve efficiency roll-off in phosphorescent yellow organic light emitting diodes

“…They include low interfacial resistance P-I-N structures, 20,21 low carrier-injection-barriers, 22,23 stepwise multi-emissive layers, 24,25 effective carrier modulation nanolayers, 26 effective carrier and exciton connement, 27,28 exciton generation on the host rather than on the guest, 29 effective host-to-guest energy transfer, 30,31 co-host structures, 32,33 and balanced carrier injection. 34,35 Similar to the phenomena observed in all reported OLEDs with other chromaticity, almost all the solution-processed yellow OLEDs showed an efficacy far much lower than the dry-processed counterparts, although low-cost, high-throughput and large-area size devices are easily achievable via a solution-process. Hence, markedly improving the efficacy of solution-processable yellow OLEDs is crucial.…”

High‐Efficiency Single Emissive Layer White Organic Light‐Emitting Diodes Based on Solution‐Processed Dendritic Host and New Orange‐Emitting Iridium Complex

“…As a result, the forward‐viewing LE, EQE, and PE of the solution‐processed WOLEDs at a luminance of 100 cd m −2 were enhanced to 70.6 cd A −1 , 26.0%, and 47.6 lm W −1 , which is a new world record for solution‐processed WOLEDs and even comparable to the reported highest efficiencies of the WOLEDs made by thermal evaporation without the need of outcoupling structures. The enhancement of the solution‐processed WOLEDs by replacing PEDOT:PSS 4083 with PEDOT:PSS 8000 may be attributed to the more balanced hole and electron flux and the reduction of leakage current since a higher proportion of PPS in PEDOT:PSS 8000 can prevent electrons from injecting into the PEDOT:PSS layer 4, 20. At a practical luminance of 500 and 1000 cd m −2 , the LE can still be kept at 48.6 and 44.3 cd A −1 , and the PE at 31.4 and 23.3 lm W −1 , respectively, and such an inevitable efficiency roll‐off is ascribed to the intrinsic triplet–triplet annihilation and charge imbalance issues at high current densities 19.…”

Effect of the chemical composition on the work function of gold substrates modified by binary self-assembled monolayers

“…[1][2][3][4][5][6][7] To reduce the injection barrier inside the organic electronic device, scientists have found several methods to modify the F of electrodes. [8][9][10][11][12][13] In particular, self-assembled monolayers (SAMs) have been used to modify the F of noble metals such as Au and Ag [14][15][16] because the work functions of these electrodes can be increased or decreased by tailoring the interfacial dipole generated by SAMs. 13,17 Work functions can also be controlled by the deposition of various SAMs on surfaces of semiconductors or organic opto-electronic devices.…”