1, We show that the so far largely ignored hydrogen bonds play a critical role in affecting the passivation of perovskite light-emitting diodes (PeLEDs). By weakening the hydrogen bonding between the passivating functional moieties and the organic cation featuring in the perovskite, we significantly enhance the interaction with defect sites and minimize non-radiative recombination losses. Consequently, we achieve exceptionally high-performance near-infrared perovskite light-emitting diodes with a record external quantum efficiency of 21.6% (Nature Photonics 13, 418, 2019)
2, We report the response of perovskite light-emitting diodes (PeLEDs) under pulsed operation. We find that for higher frequencies, the transient electroluminescence intensity depends strongly on the duty cycle. We rationalise our experimental observations using a model and assign these features to the effect of mobile ionic charges. Our work also provides important implications for the operation of PeLEDs under the steady state, where accumulation of mobile ions at the interfaces could be beneficial for high electroluminescence yields but harmful for the long-term stability. (Nature Communications 12, 4899, 2021)
3, We demonstrate spectrally stable blue PeLEDs over a wide range of emission wavelengths from 490 to 451 nanometres. The emission colour is directly tuned by modifying the halide composition. Particularly, our blue and deep-blue light-emitting diodes based on three-dimensional perovskites show high external quantum efficiency values of 11.0% and 5.5% with emission peaks at 477 and 467 nm, respectively. These achievements are enabled by a vapour-assisted crystallization technique, which largely mitigates local compositional heterogeneity and ion migration. (Nature Communications 12, 361, 2021)
4, We report an efficient solution-processed perovskite diode that is capable of working in both emission and detection modes. The device can be switched between modes by changing the bias direction. The operation speed for both functions can reach tens of megahertz. Our diodes exhibit a high specific detectivity at its peak emission, which allows an optical signal exchange between two identical diodes. To illustrate the potential of the dual-functional diode, we show that it can be used to create a monolithic pulse sensor and a bidirectional optical communication system. (Nature Electronics 3, 156, 2020)
5, We demonstrate greatly improved operational stability of high-efficiency PeLEDs, enabled by incorporating dicarboxylic acids into the precursor for perovskite depositions, resulting in amides. The formed stable amides prohibit detrimental reactions between the perovskites and the charge injection layer underneath, stabilizing the perovskites and the interfacial contacts and ensuring the excellent operational stability of the resulting PeLEDs. We achieve efficient PeLEDs with a peak external quantum efficiency of 18.6% and a long half-life time of 682 h at 20 mA cm(-2), presenting an important breakthrough in PeLEDs. (Joule 5, 618, 2021)
We presented our results at international conferences and workshops.
