Perovskite sensors - Page 2

Researchers at ETH Zurich and Empa have developed a new perovskite-based image sensor that enables better color reproduction and fewer image artefacts with less light. According to the team, perovskite sensors are also particularly well suited for machine vision.

Perovskite image sensors can theoretically capture three times as much light on the same surface area as conventional silicon image sensors – with three times the resolution. (Illustration: Sergii Yakunin / ETH Zurich / Empa)

Image sensors are ubiquitous and can be found in every smartphone, digital camera and many other electronic devices. They distinguish colors in a similar way to the human eye, where individual cone cells recognize red, green and blue (RGB). In image sensors, individual pixels absorb the corresponding wavelengths and convert them into electrical signals. The vast majority of image sensors are made of silicon. This semiconductor material normally absorbs light over the entire visible spectrum. In order to manufacture it into RGB image sensors, the incoming light must be filtered. Pixels for red contain filters that block (and waste) green and blue, and so on. Each pixel in a silicon image sensor thus only receives around a third of the available light.

Researchers from Lukasiewicz Research Network - PORT Polish Center for Technology Development, CINTRA (CNRS-International-NTU-THALES Research Alliance), Universitas Indonesia, Nicolaus Copernicus University in Torun and Institut Lumiere Matiere UMR 5306 CNRS have scaled up a new type of light-emitting material - known as a scintillator - by  embedding it with nano-engineered metallic structures, unlocking performance  previously thought unattainable in bulk materials.

Scintillators are special substances that emit visible light when exposed to  high-energy radiation like X-rays or gamma rays. They are critical in numerous fields, from medical imaging and security screening to high-energy physics experiments. But traditional scintillators have limitations: they often emit weak signals or respond slowly, making them less efficient for demanding applications. Nanoplasmonics - a field that manipulates the behavior of light on the  nanoscale using tiny metallic structures - could address this.

Researchers from Soochow University and Yangzhou University have developed a single photodiode sensor that detects full-color light using perovskite materials, impedance data, and machine learning algorithms.

While conventional photodetectors are able to measure how much light is present, they typically can't identify what kind of light it is. Extracting color or spectral information usually requires added hardware—filters, lens stacks, or multiple detectors arranged side by side or layered vertically. These systems tend to be bulky, expensive, and hard to scale, particularly when designing small, low-power devices. Even more recent strategies, like using heat or voltage to modulate a detector’s response, introduce other trade-offs, such as slower operation and higher instability.

Triboelectric nanogenerators (TENGs) based on halide perovskites are considered attractive thanks to their high output performance as micro-nano energy sources. However, the presence of toxic lead and environmental instability hamper their practical applications in wearable electronics. 

To address these challenges, researchers from Shandong University and Henan University have developed a lead-free bismuth halide perovskite, CsBi₃I₁₀ (CBI), integrated with polyvinylidene fluoride (PVDF) in a nanofiber composite film via a one-step electrospinning deposition process, serving as an alternative triboelectric layer for TENGs. 

Researchers from the Indian Institute of Technology Guwahati have reportedly developed a perovskite-based approach to detecting harmful metals like mercury in living cells and the environment.

The team relied on perovskites' unique interaction with light, which enables them to serve as fluorescent probes inside living cells. However, their quick degradation in water has previously limited their applications. To address this, the researchers encapsulated the perovskite nanocrystals in silica and polymer coatings, significantly enhancing their stability and luminescent intensity in water. This modification ensures the nanocrystals maintain their functionality over extended periods, making them highly effective for practical use.

Researchers from the Beijing National Laboratory for Molecular Sciences (BNLMS), CPU Hydrogen Power Technology (Suzhou), Fudan University, Chinese Academy of Sciences and Zhengzhou University have developed smart glasses that track eye position using arrays of perovskite light sensors instead of cameras or contact lenses. Their system measures light reflected from the eyeball to determine gaze direction with five-degree precision. 

The researchers solved a key materials challenge by developing a novel crystal growth method inspired by biological mineralization processes. They added a layer of polyacrylic acid sodium (PAAS) that guides perovskite crystals to form in larger, more organized structures – similar to how sea creatures control shell formation. This resulted in methylammonium lead iodide films with superior light-detecting capabilities.

Hybrid perovskites show piezoelectric properties due to polarization and centro-symmetry breaking of PbX₆ pyramids (X = I^-, Br^-, Cl^-). Researchers from The Hebrew University of Jerusalem, Polish Academy of Sciences and Nanyang Technological University recently examined the piezoelectric response of quasi-2D perovskites using various barrier molecules: benzyl amine (BzA), phenylethyl amine (PEA), and butyl diamine (BuDA).

Utilizing piezoelectric force microscopy measurements, the team determined the piezoelectric coefficient (d33) where BuDA exhibits a substantial response with values of 147 pm V^–1 for n = 5, better than the other quasi-2D and 3D perovskite counterparts. Density functional theory calculations revealed distorted bond angles in the PbBr₆ pyramids for quasi-2D perovskites, enhancing symmetry breaking. 

Researchers from Shanghai Jiao Tong University, Hefei University of Technology, Korea Advanced Institute of Science and Technology and Tianjin Jinhang Computing Technology Research Institute have developed a retinomorphic hardware prototype that uses a 4096-pixel perovskite image sensor array as core module to endow embodied intelligent vision functionalities. 

(A) Adaptive sensing-perception by the biological visual system through the hierarchy of photoreceptors, horizontal cells, bipolar cells, amacrine cells, and ganglion cells. (B) Schematic illustration and working principle of the retinomorphic computing system based on a 4096-pixel 1T-1PD perovskite RSA, microcontroller unit (MCU), and field-programmable gate array (FPGA). ADC, analog-to-digital converter; TIS, trans-impedance amplifier; DAC, digital-to-analog converter. Image from: Science Advances

The team explained that retinomorphic systems that can see, recognize, and respond to real-time environmental information could extend the complexity and range of tasks that an exoskeleton robot can perform to better assist physically disabled people. However, the lack of ultrasensitive, reconfigurable, and large-scale integratable retinomorphic devices and advanced edge-processing algorithms makes it difficult to realize retinomorphic hardware.

Radiation detectors, which convert radiation into measurable light signals, currently come in fixed shapes like blocks or cylinders because they are made by growing crystals at extremely high temperatures – around 1700 °C. These rigid shapes make it difficult to measure radiation doses accurately around irregularly shaped tumors or in tight spaces. Previous attempts to create detectors in custom shapes have focused on plastic materials that can be easily molded, but these plastic detectors perform poorly because they lack the heavy elements needed to efficiently capture radiation. Scientists have tried mixing metal particles into plastics to improve their detection ability, but this often results in uneven distribution of the particles and poor overall performance.

A research team from several institutions in Italy and Switzerland has now developed a new approach using stereolithography (SLA), a precise form of 3D printing that builds objects by hardening light-sensitive liquid materials layer by layer. This marks the first successful use of SLA to fabricate 3D-printed scintillators, a breakthrough in radiation detection technology. The team mixed microscopic crystals of cesium lead bromide (Cs₄PbBr₆), a perovskite material, into a liquid resin that hardens when exposed to ultraviolet light. Perovskites have gained significant attention in recent years because they efficiently convert various forms of energy into light. Their crystal structure, which contains heavy elements like lead, makes them particularly effective at detecting radiation.

Researchers from the Chinese Academy of Sciences (CAS), Beihang University and Imperial College London have developed an on-chip integrated polarization photodetector (pol-PD), drawing inspiration from the unique polarization vision of desert ants.

Working mechanism diagram of the single-shot on-chip pol-PD. Image from Science Advances

Pol-PDs have widespread applications in geological remote sensing, machine vision and biological medicine. However, commercial pol-PDs usually require bulky and complicated optical components and are difficult to miniaturize and integrate. The researchers observed that desert ants can navigate back to their nests across barren landscapes without landmarks, thanks to their compound eyes' ability to detect polarized sunlight. They aimed to mimic this capacity with their pol-PD.