Perovskite nanocrystals of the form FAPbBr3 display significant promise in the field of optoelectronics. In particular, these nanocrystals could bridge the `green gap' of LED technology, and also serve to down-convert ultraviolet light for harvesting using silicon-based photovoltaic cells. To remain competitive with traditional devices, optimising the energy transfer between the nanocrystal and the device is crucial, however very little investigation has been performed into this subject.
Here, we characterise the energy transfer dynamics of FAPbBr3 nanocrystals on a silicon substrate using time resolved photoluminescence. We also use deposited `spacer layers' to vary the displacement of the nanocrystals from the silicon in order to observe the effect on the energy-transfer dynamics. We find that the overall photo luminescent lifetime increases when reducing the distance between between the nanocrystals and the silicon layer, which runs counter to the expected behaviour. This suggests that the presence of an optically-active substrate suppresses photo luminescent lifetime and, further, suggests that nanocrystal-to-nanocrystal transfer is highly efficient.
In this work, we probe the photodegradative behaviour of CsPbBr3 perovskite nanocrystals under illumination intensities in excess of 1 W=cm2. In doing so, we uncover optical behaviours unique to this extreme form of degradation namely a pronounced period of increasing photoluminescent intensity at the outset of degradation along with a red-shifted emission lobe.
We also compare the photochemical lifetimes of CsPbBr3 to the relating organic-inorganic hybrid of FAPbBr3 and show that FAPbBr3 can withstand such high intensities for approximately ten times longer than CsPbBr3. This marks out FAPbBr3 as a potential successor to CsPbBr3 in optoelectronic applications.