Application of Naphthalenediimide Derivatives as Self-Assembled Electron Selective Contacts in CdSe@ZnS Quantum Dots LEDs

Abstract

Despite the successful application of self-assembled molecules (SAMs) as hole-selective contacts in light-emitting diodes (LEDs), examples of the use of electron-selective SAMs are scarce. Here, we investigate the potential of naphthalene diimide (NDI) as an efficient electron-selective contact in CdSe@ZnS-based LEDs. CdSe@ZnS quantum dots, due to their exceptional optical properties, have found a range of applications in optoelectronics. In particular, they have been widely studied in LEDs because of their stability, tunable and narrow emission, and high photoluminescence quantum yields. In this work, two SAMs based on NDI cores have been synthesized, incorporating different terminal groups to study their structure-device function relationship. SAM3 contains one carboxylic acid moiety and one long alkyl chain as its substituents, whereas in SAM12, both substituents are carboxylic acids. Both inverted (n-i-p) and regular (p-i-n) device configurations have been explored and analyzed and our results show that the substituents play an important role in controlling device characteristics. Therefore, the application of NDI derivatives as electron selective contacts have been demonstrated opening the door for further research into the underexplored field of electron selective SAMs in optoelectronic devices.