Waterproof Flexible InP@ZnSeS Quantum Dot Light‐Emitting Diode

Abstract

The development of flexible displays for wearable electronics applications has created demand for high‐performance quantum dot (QD) light‐emitting diodes (QLEDs) based on QD core@shell structures. Emerging indium phosphide (InP)‐based core@shell QDs show promise as lighting material in the field of optoelectronics because they are environmentally friendly material, can be produced in a cost‐effective manner, and are capable of tunable emission. While efforts have been made to enhance the performance of InP‐based QLED, the stabilities of InP@ZnSeS QDs film and InP@ZnSeS‐based QLED in water/air are not yet fully understood, limiting their practical applications. Herein, a highly durable, flexible InP@ZnSeS QLED encapsulated in an ultrathin film of CYTOP, a solution‐based amorphous fluoropolymer, is demonstrated. The CYTOP‐encapsulated green flexible QLED shows an external quantum efficiency (EQE) of 0.904% and a high luminescence of 1593 cd m−2 as well as outstanding waterproof performance. The flexible device emits strong luminescence after being immersed in water for ≈20 min. Even when subjected to continuous tensile stress with a 5 mm bending radius, the high luminescence is preserved. This waterproof architecture can be a promising strategy for wearable electronics applications.

Universal Flexible Lamination Encapsulation Strategy toward Underwater-Operation Electroluminescence Devices

“…The underwater LT 50 of the flexible QLEDs can reach 5980 s (>1.5 h). To the best of our knowledge, this was the most stable flexible QLEDs for underwater applications. , …”

“…Till date, several flexible encapsulation methods, including thin-film and lamination encapsulation, have been developed for flexible electronics. − Although these approaches have achieved some success in flexible applications in ambient air, the formation of tiny cracks and pinholes in the packaging layer and/or edge remains big issues for underwater applications. , The water molecules could penetrate into devices through these defects under water, which largely deteriorates the performance and lifetime of the devices. Lami encapsulation is one of the most promising approaches for flexible applications, which stands out for their versatility in terms of choice of encapsulating layers, scalability, and suitability for roll-to-roll lamination. , However, the sealant or adhesive used in the lamination processes might cause contamination and parasitic permeation issues, especially when directly contacted with water. , As of today, the flexible encapsulation method toward underwater applications for flexible LEDs is still in infancy. , It is therefore quite urgent and important to develop an effective encapsulation strategy that can be scalable and suitable for roll-to-roll process to expand applications of LEDs under water.…”

Solution-processed colloidal quantum dots for light emission

“…QDs, therefore, enable higher colour quality and lower power consumption in lighting sources. ( (9,35,(69)(70)(71)(72)(73). The lifetime of the QD LED devices has also significantly improved over the years, increasing from 100 hours to upwards of 1400 hours.…”

“…This has pushed the development of other materials such as InP and CuInZnS based QDs. 9,34,[76][77][78][79][80] The lifetime of the QD LED devices has also significantly improved over the years, increasing from 100 hours to upwards of 1400 hours. Lifetime of an LED is based on the time it takes for the luminescence intensity to decay to a specific level.…”

Advances and Challenges in Heavy-Metal-Free InP Quantum Dot Light-Emitting Diodes

“…To suppress the non-radiative progress, double-shell QDs were fabricated [ 72 ]. The conventional shell materials used in InP QDs are GaP, ZnS, ZnSe, and ZnSeS [ 6 , 73 , 74 , 75 , 76 ], as shown in Figure 5 . Among them, the lattice mismatch between ZnSe and InP is the smallest, at only 3.3%; GaP reaches 7.1%; and ZnS is the largest, which is 7.7% [ 70 , 73 , 74 , 77 , 78 ].…”