Harvesting the Triplet Excitons of Quasi-Two-Dimensional Perovskite toward Highly Efficient White Light-Emitting Diodes

Abstract

Utilization of triplet excitons, which generally emit poorly, is always fundamental to realize highly efficient organic light-emitting diodes (LEDs). While triplet harvest and energy transfer via electron exchange between triplet donor and acceptor are fully understood in doped organic phosphorescence and delayed fluorescence systems, the utilization and energy transfer of triplet excitons in quasitwo-dimensional (quasi-2D) perovskite are still ambiguous. Here, we use an orangephosphorescence-emitting ultrathin organic layer to probe triplet behavior in the skyblue-emitting quasi-2D perovskite. The delicate white LED architecture enables a carefully tailored Dexter-like energy-transfer mode that largely harvests the triplet excitons in quasi-2D perovskite. Our white organic−inorganic LEDs achieve maximum forward-viewing external quantum efficiency of 8.6% and luminance over 15 000 cd m −2 , exhibiting a significant efficiency enhancement versus the corresponding sky-blue perovskite LED (4.6%). The efficient management of energy transfer between excitons in quasi-2D perovskite and Frenkel excitons in the organic layer opens the door to fully utilizing excitons for white organic−inorganic LEDs.

Perovskite‐Organic Coupling WLED: Progress and Perspective

“…In addition to the isolation or luminescence functions shown in Figure 3a,b, organic molecules with both isolation and luminescence properties can also be introduced into POC-WLED. Recently, Yu et al [75] reported a POC-WLED architecture with an ultrathin organic layer as the orange component and perovskite as the blue component, as shown in Figure 3c. It is found that the inserted spacer can block holes and inhibit the concentration quenching in the organic light-emitting layer.…”

“…Recently, Yu et al. [ 75 ] reported a POC‐WLED architecture with an ultrathin organic layer as the orange component and perovskite as the blue component, as shown in Figure 3c. It is found that the inserted spacer can block holes and inhibit the concentration quenching in the organic light‐emitting layer.…”

“…c) Energy levels of the designed white LEDs and EL spectra at a current density of 5 mA cm −2 of the blue and white devices shown in the inset. Reproduced with permission [75]. Copyright 2022, American Chemical Society.…”

Photoexcitation Control of Excitation Relaxation in Mixed‐Phase Ruddlesden‐Popper Hybrid Organic‐Inorganic Lead‐Iodide Perovskites

“…[14] The existence and the impact of singlet and triplet states in low-dimensional materials and in different perovskite materials has been investigated by several groups providing different approaches how to overcome the splitting and hence improve the emission. [14][15][16][17][18] For low-dimensional semiconductors, enhancing the photoluminescence is not only possible via transitions between singlet-triplet states but also via phonon-assisted radiative recombination. [19][20][21][22] Furthermore, efficient transfer processes are crucial for bright luminescence.…”

“…[ 14 ] The existence and the impact of singlet and triplet states in low‐dimensional materials and in different perovskite materials has been investigated by several groups providing different approaches how to overcome the splitting and hence improve the emission. [ 14‐18 ]…”