From InAs Cores to Thick Shell InAs/ZnSe Core/shells: Boosting Near-Infrared LED Performance
Creators: name: Roshan, Hossein
name: Zhu, Dongxu
name: Davide, Piccinotti
name: Jinfei, Dai
name: Manuela, De Franco
name: Matteo, Barelli
name: Mirko, Prato
name: De Trizio, De Trizio
name: Manna, Liberato
name: di Stasio, Francesco
Publisher: name: Zenodo
Year: 2023
Subjects: QD-LED
InAs
Infrared
Quantum Dot
Electroluminescence

description: In the quest for heavy-metal-free colloidal quantum dots (QDs) for optoelectronic devices, III-V QDs demonstrate promising characteristics. Specifically, InAs QDs exhibit commendable absorption and emission properties in the near-infrared spectral range, . Traditional methods for obtaining InAs QDs involve the use of highly reactive, pyrophoricand expensive chemicals, such as tris-trimethylsilyl (TMS) arsine and TMS phosphine, which are not conducive to scalable material production. These InAs QDs have been utilized in light-emitting diodes (LEDs) with external quantum efficiencies (EQEs) of 4.6% and 13.3%, paired with InP and GaP shells, respectively. In our approach, we developed a synthetic method for InAs QDs and their core-shell structures using alternative, cost-effective, and less hazardous arsenic precursors, such as tris(dimethylamino)-arsine (amino-As). In a previous publication, we applied this innovative methodology, incorporating (amino-As), alane N,N-dimethylethylamine as a reducing agent, and ZnCl2 as an additive, for the synthesis of InAs/ZnSe core/shell QDs, achieving a shell thickness of approximately 1.5 monolayers (ML). This resulted in a peak emission wavelength at 860 nm in solution and a substantial photoluminescence quantum yield (PLQY) of around 42% [1]. Using these QDs, we developed an LED with a turn-on voltage of 2.7V, EQE of 5.5%, and maximum radiance of 0.2 Wsr-1cm-2 [2].

Building on these findings, we increased the ZnSe shell thickness to 7 ML, leading to a notable enhancement of the PLQY, now reaching approximately 70% at a peak emission wavelength of 906 nm in solution [3]. We employed such QDs for the fabrication of LEDs with an inverted architecture. Here, we present the optimized LED architecture, which consist of ZnO as electron transport layer and Poly-TPD as hole transport layer. The results of thick shell InAs/ZnSe LED show a significant improvement in LED performance, including reduced turn-on voltage, increased maximum EQE, maximum radiance and dynamic range. Importantly, the best performing LED achieves an EQE of 13.3% and a radiance of 12 Wsr-1cm-2.

 

[1] Zhu, D.; Bellato, F.; Bahmani Jalali, H.; Di Stasio, F.; Prato, M.; Ivanov, Y. P.; Divitini, G.; Infante, I.; De Trizio, L.; Manna, L. ZnCl 2 Mediated Synthesis of InAs Nanocrystals with Aminoarsine. J. Am. Chem. Soc. 2022, 144 (23), 10515–10523.

[2] De Franco, M.; Zhu, D.; Asaithambi, A.; Prato, M.; Charalampous, E.; Christodoulou, S.; Kriegel, I.; De Trizio, L.; Manna, L.; Bahmani Jalali, H.; Di Stasio, F. Near-Infrared Light-Emitting Diodes Based on RoHS-Compliant InAs/ZnSe Colloidal Quantum Dots. ACS Energy Lett. 2022, 3788–3790.

[3] Zhu, D.; Bahmani Jalali, H.; Saleh, G.; Di Stasio, F.; Prato, M.; Polykarpou, N.; Othonos, A.; Christodoulou, S.; Ivanov, Y. P.; Divitini, G.; Infante, I.; De Trizio, L.; Manna, L. Boosting the Photoluminescence Efficiency of InAs Nanocrystals Synthesized with Aminoarsine via a ZnSe Thick‐Shell Overgrowth. Adv. Mater. 2023, 35 (38).