Proceedings of nanoGe Fall Meeting 2021 (NFM21)
Publication date: 23rd September 2021
The performance of perovskite light-emitting diodes (PeLEDs) has advanced quickly during the past few years. High external quantum efficiencies (EQEs) over 20% have been reached for various colours. However, further parameters play an important role when employing LEDs in real-world applications. Of particular importance in display and visible light communication (VLC), two important applications for LEDs, is pulsed operation, which has not yet been investigated, although it is expected that the ionic conductivity will influence this mode of operation. Here, we report the response of infrared (NIR) PeLEDs under pulsed operation in the range of 10 Hz to 20 kHz. Beyond transient effects in the low frequencies, we find that for higher frequencies (> 500 Hz) the transient electroluminescence (TrEL) intensity depends strongly on the duty cycle, an unprecedented and never observed feature in conventional LEDs. We rationalise our experimental observations using a mathematical model to describe the TrEL signal. We assign the unprecedented feature including a concomitant EL overshoot after turning off the driving voltage, to the effect of mobile ionic charges in the perovskite. We conclude that accumulation of mobile ionic charges at the interfaces could be essential to reach high EL yields in general in PeLEDs. Our work provides new understanding to the operation of PeLEDs, especially in the pulsed mode which is crucial for displays, lasers and VLC technology. In addition, an EL signal depending on the preceding share of on-time constitutes a memory-feature that might become interesting for novel computing based on simultaneous information processing and storage in one device.
We thank Pengpeng Teng, Jian Qing, Heyong Wang, and Weidong Xu for providing us perovskite light-emitting diodes (PeLEDs). We acknowledge the support from the ERC Starting Grants (No. 717026 and No. 851676), the Swedish Energy Agency Energimyndigheten (No. 48758-1 and 44651-1), and the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO-Mat-LiU No. 2009-00971).
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