Halide perovskites – already a focus of major research into efficient, low-cost solar cells – have been shown to handle light faster than most semiconductors on the market.
The paper, published in Nature Nanotechnology, reports quantum transients on the scale of ~2 picoseconds at low temperature in bulk formamidinium lead iodide films grown by scalable solution or vapour methods. That ultrafast timescale indicates use in very fast light sources and other photonic components. Crucially, these effects appear in films made by scalable processing rather than specialised growth in lab-settings – suggesting a practical and affordable route to explore ultrafast quantum technology.
"Perovskites continue to surprise us," said Professor Sam Stranks, who led the study. "This discovery shows how their intriguing nanoscale structure gives rise to intrinsic quantum properties that could be harnessed for future photonic technologies."
Joint first authors in Prof Stranks' Optoelectronic Materials and Device Spectroscopy Group, post-doctoral researcher Dr Dengyang Guo and PhD student Tom Selby, combined ultrafast spectroscopy with optical and electron microscopy to pinpoint the origin of the effect. The team attribute the rapid emission to quantum tunnelling in ordered nanodomain superlattices – alternating structural domains within the material that create the conditions for very fast radiative recombination.
Dr Guo said: "Seeing these ultrafast effects in scalable films is exciting. It shows perovskites have even more to offer than we realised, beyond solar cell optimisation."
Selby added: "Being able to trace the emission back to the structure has been an eye-opener – it is really exciting to consider the potential of what this research could lead to."
The study emphasises both opportunity and caution. The ultrafast transients point to potential applications – ultrafast emitters or increased accuracy in measurements for example. But the measurements were carried out at low temperature, and the paper does not report room-temperature performance or quantum-optics metrics such as single-photon purity or indistinguishability. It does, however, further demonstrate the multi-use potential of halide perovskites.
