Identification and Mitigation of Transient Phenomena That Complicate the Characterization of Halide Perovskite Photodetectors.

Halide perovskites have shown promise to advance the field of light detection in next-generation photodetectors, offering performance and functionality beyond what is currently possible with traditional inorganic semiconductors. Despite a relatively high density of defects in perovskite thin films, long carrier diffusion lengths and lifetimes suggest that many defects are benign. However, perovskite photodetectors show detection behavior that varies with time, creating inconsistent device performance and difficulties in accurate characterization. Here, we link the changing behavior to mobile defects that migrate through perovskites, leading to detector currents that drift on the time scale of seconds. These effects not only complicate reproducible device performance but also introduce characterization challenges. We demonstrate that such transient phenomena generate measurement artifacts that mean the value of specific detectivity measured can vary by up to 2 orders of magnitude even in the same device. The presence of defects can lead to photoconductive gain in photodetectors, and we show batch-to-batch processing variations in perovskite devices gives varying degrees of charge carrier injection and photocurrent amplification under low light intensities. We utilize the passivating effect of aging to reduce the impact of defects, minimizing current drifts and eliminating the gain. This work highlights the potential issues arising from mobile defects, which lead to inconsistent photodetector operation, and identifies the potential for defects to tune photodetection behavior in perovskite photodetectors.

Tunable Multiband Halide Perovskite Tandem Photodetectors with Switchable Response.

Photodetectors with multiple spectral response bands have shown promise to improve imaging and communications through the switchable detection of different photon energies. However, demonstrations to date have been limited to only two bands and lack capability for fast switching in situ. Here, we exploit the band gap tunability and capability of all-perovskite tandem solar cells to demonstrate a new device concept realizing four spectral bands of response from a single multijunction device, with fast, optically controlled switching between the bands. The response to monochromatic light is highly selective and narrowband without the need for additional filters and switches to broader response bands on applying bias light. Sensitive photodetection above 6 × 1011 Jones is demonstrated in all modes, with rapid switching response times of <250 ns. We demonstrate proof of principle on how the manipulation of the modular multiband detector response through light conditions enables diverse applications in optical communications with secure encryption.

Halide perovskites scintillators: unique promise and current limitations.

The widespread use of X- and gamma-rays in a range of sectors including healthcare, security and industrial screening is underpinned by the efficient detection of the ionising radiation. Such detector applications are dominated by indirect detectors in which a scintillating material is combined with a photodetector. Halide perovskites have recently emerged as an interesting class of semiconductors, showing enormous promise in optoelectronic applications including solar cells, light-emitting diodes and photodetectors. Here, we discuss how the same superior semiconducting properties that have catalysed their rapid development in these optoelectronic devices, including high photon attenuation and fast and efficient emission properties, also make them promising scintillator materials. By outlining the key mechanisms of their operation as scintillators, we show why reports of remarkable performance have already emerged, and describe how further learning from other optoelectronic devices will propel forward their applications as scintillators. Finally, we outline where these materials can make the greatest impact in detector applications by maximally exploiting their unique properties, leading to dramatic improvements in existing detection systems or introducing entirely new functionality.