Perovskite Nanocrystal Light‐Emitting Diodes with Ultralow Drive Voltage Realized by Auger‐Assisted Energy Up‐Conversion

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Abstract
Reducing the driving voltage is a long‐term and important challenge in the development of light‐emitting diodes (LEDs) because the light‐emission threshold voltage cannot be below the theoretical limit of the emitter's bandgap divided by the elementary charge. Here, green perovskite nanocrystal (PeNC) LEDs are inverted that emit light at ultralow voltages (below the theoretical limit) realized by efficient Auger‐assisted energy up‐conversion at the interface of the zinc oxide nanoparticles (ZnO NPs) electron injection layer and PeNC light‐emission layers. The up‐conversion utilizes the recombination energy of the charge‐transfer excitons. After modifying the interface by plasma treatment of the ZnO NPs and by inserting an organic interlayer between the ZnO NPs and PeNCs, the device performance is dramatically improved from that of the unmodified PeNC LED. The threshold voltage at which the emission spectrum can be observed is 1.55 V, substantially lower than 2.34 V (the PeNC emitter's bandgap divided by the elementary charge). Moreover, after mixing an organic aromatic semiconductor compound in the PeNC light‐emission layer, the carrier balance is regulated and the threshold voltage is further reduced to 1.30 V.
Funding Information
  • Strategic International Collaborative Research Program (JPMJSC2111)
  • Japan Science and Technology Agency

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