I. Abstract of the Paper’s Core Research

• In-situ crystallization–induced three-dimensional perovskite absorber structure with aerosol‑based fabrication

During the flight of atomized droplets, (MA)(DMF) PbI₃ intermediate needle-like crystals precipitate; upon deposition, low-temperature solvent removal converts these into pure MAPbI₃. A 600 μm‑high perovskite absorber wall can be printed layer by layer, and the resulting three-dimensional architecture significantly enhances X-ray photon capture efficiency, with printed pixel sizes as small as 48.7 μm.

• Graphene‑based composite heterojunctions achieve ultra‑high X‑ray detection sensitivity.

Perovskite-generated electrons are injected into graphene, yielding photoelectric gain; in the low-dose regime under 8 keV X‑ray irradiation, the sensitivity reaches 2.2 × 10⁸ μC Gy⁻¹ cm⁻², an improvement of four orders of magnitude compared with conventional perovskite devices. The detection limit is as low as 0.12 μGy/s, enabling medical imaging at ultra‑low radiation doses.

• Wide‑range, stable, linear response; low bias and low‑power operation.

The device exhibits excellent signal linearity across the 0.12–358 μGy/s range, delivering a stable photocurrent even at an ultra-low bias of 100 mV, thereby significantly reducing drive power consumption. At high doses, only slight signal saturation is observed, resulting in a broad dynamic detection range.

• Long-term environmental and radiation dual-stability performance

After PDMS encapsulation, the device exhibits no significant performance degradation after 9 months of storage at room temperature; under continuous high-energy X-ray irradiation, it demonstrates a nano‑scale self‑healing effect, enabling spontaneous recovery from radiation damage and enduring long‑term, continuous scanning conditions.

• Rapid Fabrication of Digital Maskless 3D Pixel Arrays

CAD‑based customization of lines, grids, and columnar absorption structures eliminates the need for complex microfabrication steps such as photolithography, evaporation, and lift‑off. Glass and flexible substrates can both be directly printed to form imaging pixel arrays, significantly shortening the R&D iteration cycle.

II. Complete 3D Perovskite Detector Process and Core Advantages for Aerosol Jet Printing

(1) Complete Device Fabrication Process

• Ti/Au metal electrodes are deposited on a Si/SiO₂ substrate, followed by CVD graphene transfer and patterning.
• MAPbI₃ perovskite powder is dissolved in DMF to prepare a dedicated aerosol ink, which is thoroughly dispersed by sonication.
• AJ300 ultrasonic atomization, with adjustable carrier and sheath gas flow rates, enables multi-layer, repeated printing to construct micron‑scale thick perovskite 3D walls.
• Stepwise low-temperature annealing at 45–70°C enables the complete conversion of the solvated mesophase into pure perovskite crystals.
• PDMS encapsulation provides moisture barrier protection, and an X-ray irradiation test platform was established to perform imaging performance calibration.

(II) Five Major Process Advantages (Comparison of Lithography, Spin Coating, and Inkjet Printing)

• The only additive manufacturing process capable of directly printing three-dimensional thick absorptive layers.

Spin coating and inkjet printing can only fabricate thin two-dimensional films, whereas aerosol‑based layer‑by‑layer stacking enables the formation of three-dimensional perovskite structures hundreds of micrometers tall. The incorporation of heavy‑metal layers enhances X‑ray absorption, leading to a dramatic leap in sensitivity.

• In-situ pre-crystallization of droplets eliminates spreading‑related short‑circuit defects.

During the droplet‑flight stage, needle‑like intermediate crystals form prematurely; upon landing, the solvent content is minimal, preventing lateral spreading and dissolution of the underlying circuitry. The multilayered three‑dimensional structure exhibits no crosstalk or leakage current.

• Micrometer-level precise localized deposition with crisp pixel boundaries.

The minimum print spot size is 48.7 μm, enabling the independent fabrication of isolated imaging pixels. Optical and electrical crosstalk between array pixels is extremely low, resulting in higher imaging contrast.

• Low-temperature, mild forming process that does not compromise the flexibility of graphene electrodes.

The entire process employs heat treatment below 70°C, ensuring that graphene and the PI flexible substrate do not undergo high-temperature oxidation or warping, and are compatible with flexible curved‑surface imaging detectors.

• No lithography, no vacuum—significantly reducing the R&D costs of imaging chips.

By eliminating high‑cost processes such as electron-beam lithography, lift‑off, and multilayer evaporation, desktop aerosol‑based equipment enables rapid prototyping of various pixel‑array architectures.

III. Five Core Technological Innovations of This Study

Innovation 1: A novel in-situ solvent-assisted crystallization process for aerosol‑based 3D perovskites

Innovative 2 Perovskite/Graphene Heterojunction Optoelectronic Gain Architecture

Innovative 3‑Channel Ultra‑Wide Dynamic Range Low‑Dose X‑Ray Detection System

Innovative 4‑ray irradiation self‑healing + encapsulation long‑term dual‑stability solution

Innovation 5: A Rapid Manufacturing Paradigm for Fully Digital Three-Dimensional Imaging Arrays

IV. Existing Process Challenges and Corresponding Solutions for Overcoming Them

Challenge 1: Conventional solution-based processes can only fabricate thin perovskite films, resulting in weak X-ray absorption and low sensitivity.

Challenge 2: Spin-coating and inkjet inks exhibit large‑area spreading on the substrate, resulting in blurred pixel boundaries and severe array crosstalk.

Challenge 3: In single‑phase perovskite thin films, radiative recombination of photogenerated carriers is severe, making it impossible to detect weak X‑ray signals.

Challenge 4: Perovskites are susceptible to moisture, and high-energy irradiation can cause permanent damage.

Challenge 5: Photolithographic microfabrication is costly and time-consuming, making it difficult to rapidly iterate on imaging array designs.

V. Future Diversified Industrial Application Scenarios

• Low-dose medical CT and dental X-ray imaging chips

• Industrial Nondestructive Ultra-Thin Curved-Surface Flaw Detection Equipment

• Portable Trace Radiation Imaging Device for Security Screening

• Space Aerospace Lightweight Radiation Detection Module

• High-Performance Optoelectronics and Medical Imaging Laboratory Rapid Prototyping Platform

Figure 1. Three-dimensional MAPbX3 aerosol jet printing. (a) Schematic of the AJP system. A focused nitrogen gas jet promotes rapid solvent evaporation and the growth of an intermediate phase (see text), which is crucial for forming well-defined three-dimensional structures. (b–g) Various MAPbI3 patterns fabricated on glass substrates, including linear, helical, grid-like, and columnar architectures.

Figure 2. Crystallization process of MAPbI3 from the intermediate solvent‑phase state. (a) Experimental X‑ray diffraction patterns recorded during crystallization, illustrating the transformation from the intermediate phases (MA)(DMF)PbI3 and (MA)₂(DMF)₂Pb₃I₈ to MAPbI3. Diffraction peaks associated with MAPbI3, as well as those absent in all intermediate phases, are marked with red circles. (b) Schematic model of MAPbI3 formation in (MA)(DMF)PbI3, based on structural analysis (space group P21/c; a = 4.5647(9) Å, b = 25.446(5) Å, c = 12.119(2) Å, β = 96.75(3)°). The filamentary MAPbI3 grows along the direction perpendicular to the (011) crystal plane of (MA)(DMF)PbI3.

Figure 3. MAPbX3/graphene heterostructure sensing unit for photodetection. (a) Schematic side view of the sensing unit; (b) Top-view false-color scanning electron microscope image showing AJP‑deposited MAPbI3 columnar structures (purple) on a graphene layer (blue) and gold electrodes (yellow). (c) Visible-light‑induced photocurrent response curve under a 10 mV bias.

Figure 4. X-ray detector measurement results. (a) Photograph of the fully integrated X-ray detector; (b) A sensing chip with an area of 1 cm² and a 3D-printed MAPbI₃ wall approximately 600 μm thick; (c) A false-color SEM image of the 3D-printed MAPbI₃ wall on Ti/Au electrodes (graphene appears blue, MAPbI₃ appears purple, and the metal electrodes appear yellow); (d) The time-dependent photocurrent response induced by X-ray irradiation under a 100 mV bias; (e) The dependence of photocurrent density on X-ray dose rate; the region below 1 μGy/s is shown in the inset.