Photodetector technologies based on emerging semiconductors—for example, organic semiconductors, halide perovskites, quantum dots, low-dimensional semiconductors and metal oxides—hold considerable promise for next-generation optoelectronics. However, the breadth and multidisciplinarity of this field, alongside its diverse range of applications, have resulted in inconsistent performance characterization and reporting practices, hindering the effective benchmarking of these technologies. Here we present a consensus among researchers from academia and industry on accurately capturing the key performance metrics of photodetectors based on emerging semiconductors and utilizing the photoelectric effect. We analyse their underlying assumptions, discuss common misunderstandings, and provide guidelines for accurate characterization and reporting. Additionally, we discuss the benchmarking of these photodetector technologies with respect to diverse applications. We expect that these comprehensive guidelines for characterization, reporting and benchmarking will accelerate and streamline further advancements in the field, propelling emerging photodetector technologies towards their full potential.

Quantum dots (QDs) have been explored for many photonic applications, both as emitters and absorbers. Thanks to the bandgap tunability and ease of processing, they are prominent candidates to disrupt the field of imaging. This review article illustrates the state of technology for infrared image sensors based on colloidal QD absorbers. Up to now, this wavelength range has been dominated by III–V and II–VI imagers realized using flip-chip bonding. Monolithic integration of QDs with the readout chip promises to make short-wave infrared (SWIR) imaging accessible to applications that could previously not even consider this modality. Furthermore, QD sensors show already state-of-the-art figures of merit, such as sub-2- $\mu \text{m}$ pixel pitch and multimegapixel resolution. External quantum efficiencies already exceed 60% at 1400 nm. With the potential to increase the spectrum into extended SWIR and even mid-wave infrared, QD imagers are a very interesting and dynamic technology segment.

A curved image sensor on plastic foil has been developed for cone beam computed tomography (CBCT) X-ray imaging. The image sensor of about 6 × 8 cm² size has been built on a thin polyimide foil with an indium gallium zinc oxide (IGZO) backplane and an organic photodetectors (OPD) frontplane. A flexible cesium iodide (CsI) scintillator has been attached to the optical sensor with 480 × 640 pixels of 126 µm size. Dark current density of the OPD was low with less than 10⁻⁷ mA/cm² at −2 V, while an external quantum efficiency (EQE) of about 50% was reached in the visible wavelength range matched to the scintillator output. The image quality of the digital X-ray detector allowed for 3D reconstruction images of a bone phantom on a rotating stage with a lab setup. The curved detector with 32 cm curvature radius opens up the path for very compact CBCT gantries with largely reduced footprint.

Colloidal quantum dots based on lead sulfide (PbS) are very attractive materials for the realization of novel image sensors. They offer low cost synthesis, compatibility with a variety of substrates and processing on large area. The tunable band gap enables selective light detection from the visible wavelengths up to the short-wave-infrared (SWIR). This work describes the roadmap towards the integration of quantum dot photodiodes (QDPD) on top of a Si based CMOS read-out circuit. Photodiodes using an n-p junction architecture are fabricated on Si substrates, showing a dark current of 30 nA/cm2 at -1 V reverse bias, EQE above 20% and specific detectivity above 1012 cm Hz1/2 W.1 at the wavelength of 940 nm. Efficiency is improved by reducing absorption in the top contact through optical design. Furthermore, photolithographic patterning of the thin-film stack is introduced for the first time, showing the feasibility of pixel pitches down to 40 μm, opening the way towards high resolution monolithic infrared imagers and the incorporation of infrared and visible sensitive pixels side by side.