Achieving Efficient Phosphorescence and Mechanoluminescence in Organic Host–Guest System by Energy Transfer

Abstract

Host-guest doping strategy greatly facilitates and expands the scope of construction of organic phosphorescence materials. Herein, triphenylamine with excellent crystallinity is chosen as the host, and four guests with 2-4 triphenylamine repeating units are chosen as the guests. The similarity in molecular structures of the host and guests simplifies the exploration of the luminescence mechanism in the doped system. The doped materials display strong room temperature phosphorescence (RTP) with above 200 ms lifetimes and 30% quantum yields. In addition, the doped system emits blue fluorescence under mechanical stimulation, that is, shows a phenomenon of mechanoluminescence (ML). The experimental results prove that the host plays different roles in different luminescence processes. In the photophosphorescence process, the triplet energy level of the host assists the guest excitons to undergo intersystem crossing. Meanwhile, in the ML process, the energy generated as a result of piezoelectric property of the host crystal is transferred to the guest, causing the guest molecules to emit fluorescence. This work is significant for the construction of doped materials with multiple luminescence properties, including RTP and ML.

Manipulation of Triplet Excited States in Two‐Component Systems for High‐Performance Organic Afterglow Materials

“…To address this issue, Dong, Cai and Lei proposed that organic matrices with T 1 levels sandwiched between S 1 and T 1 levels of organic dopants can mediate intersystem crossing of the organic dopants. [34,56,71] In the reported studies where triphenylphosphine and triphenylarsenic were used as organic matrices, luminescent dopants such as triphenylamine derivatives have been found to show wide-range color-tunable RTP properties which can serve as printable and writable security inks (Figure 6). [34] By using similar design strategy, RTP materials based on triphenylamine matrices can reach phosphorescence efficiency of 37.5 % and interesting mechanoluminescence properties.…”

“…Many organic molecules possess singlet‐triplet splitting energy ( Δ E ST ) of around 0.5 eV or even larger and consequently show small rate constants of intersystem crossing. To address this issue, Dong, Cai and Lei proposed that organic matrices with T 1 levels sandwiched between S 1 and T 1 levels of organic dopants can mediate intersystem crossing of the organic dopants [34,56,71] . In the reported studies where triphenylphosphine and triphenylarsenic were used as organic matrices, luminescent dopants such as triphenylamine derivatives have been found to show wide‐range color‐tunable RTP properties which can serve as printable and writable security inks (Figure 6).…”

“…In the reported studies where triphenylphosphine and triphenylarsenic were used as organic matrices, luminescent dopants such as triphenylamine derivatives have been found to show wide‐range color‐tunable RTP properties which can serve as printable and writable security inks (Figure 6). [34] By using similar design strategy, RTP materials based on triphenylamine matrices can reach phosphorescence efficiency of 37.5 % and interesting mechanoluminescence properties [71] . When benzophenone was used as organic matrices, highly efficient RTP materials under ambient conditions can be prepared by selecting 1‐(4‐(diphenylamino)phenyl)‐2‐phenylethan‐1‐one compounds as luminescent dopants.…”

“…[34] By using similar design strategy, RTP materials based on triphenylamine matrices can reach phosphorescence efficiency of 37.5 % and interesting mechanoluminescence properties. [71] When benzophenone was used as organic matrices, highly efficient RTP materials under ambient conditions can be prepared by selecting 1-(4-(diphenylamino)phenyl)-2-phenylethan-1-one compounds as luminescent dopants. On the basis of such dopant-matrix strategy, a recent study exhibited the fabrication of near-infrared RTP materials by doping pyrene derivatives into benzophenone matrices.…”

A New Class of Solution Processable Pyrazino[2,3‐g]quinoxaline Carbazole Derivative Based on D–A–D Architecture for Achieving High EQE in Yellow and White OLEDs

“…This improvement in efficiency by incorporating bipolar CBP host may be attributed to the following key factors: efficient energy transfer from host to guest, efficient exciton generation capability on host and guest, low electron-trap between the emissive layer and ETL, effective electron-injection and hole-blocking property of employed ETL, and surface morphologies of the emissive layer. [57][58][59][60][61][62] Moreover, the performance of devices can be influenced by absolute photoluminescence quantum yield (PLQY). [63,64] In photo luminescence, a host can have a significant impact on emitters PLQY, resulting from the polarity effect of host materials and the energy-transfer process from host to guest.…”