The humble X-ray may have received a long-overdue upgrade thanks to the development of a highly sensitive, printable X-ray detector that can operate over a wide range of energy levels.
X-rays are high-energy photons with short wavelengths and very high frequency that have been used as a medical diagnostic tool since 1896. X-rays are usually described by their maximum energy, determined by the voltage between electrodes.
The energy transported by the radiation is converted into a visual or electronic form by an X-ray detector, most of which operate in one of two energy levels, hard or soft. Those with high photon energies – above five to 10 kiloelectron volts (keV) – are called “hard X-rays” and are widely used in medical radiology because they can penetrate dense materials like bone. “Soft X-rays” usually have an energy level below 1 keV and are used to image living matter like tissues and cells.
Sometimes an X-ray detector has to operate across both energy levels, such as when searching for tumors in breast tissue. Existing detectors made of silicon and selenium can operate in hard and soft windows, but their energy sensitivity and spatial resolution – the ability to differentiate between two nearby objects – are limited.
A team led by researchers at Monash University in Melbourne, Australia, has developed a highly sensitive, multi-energy X-ray detector using technology typically associated with next-gen solar energy devices. The researchers found that metal halide perovskites were an effective, versatile alternative to silicon and selenium because they can manage the intensity of an X-ray beam as it passes through matter, a process called X-ray attenuation.
Perovskite is a naturally occurring mineral with the same crystal structure as calcium titanium oxide. It’s previously been used in studies limited to hard X-ray detection on a small scale, but this is the first time perovskites have been used to test soft X-ray detection.
In the current study, the researchers created X-ray detectors by printing a thin film of perovskite within a diode device. They found that the perovskite-based detectors operated in a broad energy range from 0.1 keV into the tens of keV, which is far wider than existing multi-energy X-ray detectors.
Because the detectors are made as a thin film, they could be combined with flexible substrates to produce a range of device shapes and sizes. Flexible X-ray detectors can be used to conform to rounded body parts or molded to fit into confined spaces.
“This work showcases that there’s a natural extension of perovskites into printed X-ray detectors,” said Jacek Jasieniak, the study’s corresponding author. “They should be cheaper to make, and could also involve modified film form factors, where you need inherent flexibility.”
The researchers foresee a wide range of real-world uses for these newly developed X-ray detectors.
“These perovskite-based detectors can provide rapid response times and offer high sensitivities to enable real-time detection and imaging for complex purposes, including disease diagnoses, detection of explosives and identifying food contamination,” said Babar Shabbir, lead author of the study.
The study was published in the journal Advanced Materials.
Source: Exciton Science
