I. Abstract of the Paper’s Core Research

• Ultrafine droplets suppress the coffee-ring effect, and the film quality surpasses that of spin coating.

The 100 kHz piezoelectric vibrating mesh generates ultrafine aerosol droplets with an average size of 5 μm, and when paired with a wide‑slot nozzle, it boosts droplet flux, thereby eliminating coffee‑ring formation at the source. The thin film exhibits superior face‑on molecular orientation, leading to enhanced crystallinity and carrier mobility. Single‑droplet‑printed devices with an active layer achieve a power conversion efficiency of 15.65%, outperforming spin‑coated counterparts using the same solvent (14.08%) and approaching the benchmark of chloroform‑spin‑coated devices (15.36%).

• Global Air Environment Three-Layer All-Aerosol Printing OSC

The HTL/PEDOT:PSS, the active layer PTQ10:Y6-BO, and the ETL/PDINO—three functional layers—were all fabricated via continuous VMA aerosol printing, without the use of a glovebox or halogenated solvents. The all-printed device achieved a power conversion efficiency of 14.78%, setting a new record for droplet-based printing in this category.

• Extremely low ink consumption, with automated production lines now in place.

The device‑pipeline startup requires only 100 mL of ink, far less than the few milliliters of consumables typically used in conventional aerosol jet printing. An integrated conveyor‑based microfabrication platform enables fully automated three‑layer printing and two annealing steps within 30 minutes, allowing for continuous batch production of devices.

• Large-area devices with stable output

A 1 cm² large-area aerosol-printed battery achieves an efficiency of 13.05%, with extremely low performance variability across devices and excellent process reproducibility.

• The thin film exhibits strong controllability.

By precisely controlling the liquid supply flow rate and the substrate‑moving speed, we can tailor the thickness of ultrathin films to 10–100 nm, while simultaneously enabling the stable fabrication of two types of functional layers: a transport layer (10–40 nm) and a light‑absorbing layer (100 nm).

II. Operating Principle of VMA Aerosol Spraying and Core Technological Advantages

(1) Complete Workflow

• Vibration mesh atomization : At 100 kHz, a piezoelectric actuator drives a micron‑scale metallic mesh to vibrate at high frequency, squeezing ink to generate uniform ultrafine droplets measuring 3–8 μm in diameter; the droplet volume is only one hundredth that of conventional ultrasonic atomization.
• Nitrogen carrier gas delivery : Inert nitrogen gas carries aerosols into a custom-designed slit‑type printing nozzle, eliminating the conventional conical spray jet;
• Slit-plane deposition : The slit nozzle reshapes the spray into a sheet‑like, wide‑width aerosol, increasing the number of droplets per unit area; the droplets coalesce rapidly upon impact, thereby suppressing annular deposition.
• Film is deposited via uniform substrate motion, with an integrated in-line annealing station, and the conveyor belt continuously performs multi-layer stack printing.

(II) A Comparison of the Five Unique Advantages of Spin Coating, Inkjet Printing, and Ultrasonic Spray Coating

• Green air processing, no inert glove box required.

Using a low‑vapor‑pressure, halogen‑free, environmentally friendly solvent based on o‑xylene, stable film formation can be achieved with ambient air at 30% relative humidity, eliminating the need for costly, sealed, oxygen‑free production lines and significantly reducing capital expenditures for plant construction.

• Ultrafine droplets completely eliminate the fatal flaw of coffee rings.

Inkjet printing and conventional spray techniques produce large droplets with rapid solvent evaporation, leading to pronounced edge‑thick, center‑thin profiles. In contrast, VMA generates micron‑scale droplets that coalesce thoroughly, yielding a thin film with an RMS roughness of only 0.91 nm—comparable to spin‑coated films.

• Consumable costs have plummeted.

The initial ink priming requires only 100 mL, and spin coating results in 90% of the material being flung off, while inkjet delivery systems consume substantial amounts of ink—making this approach exceptionally well-suited for high‑cost organic photovoltaic materials.

• Ultra-thin, wide‑width, one‑piece molding that meets the requirements of multi‑layer films.

It enables the simultaneous fabrication of a 10-nm-thick transport layer and a 100-nm-thick active layer, with a single slot‑die nozzle facilitating large‑area continuous printing—eliminating the need for row‑by‑row stitching and preventing stripe‑like defects.

• Compatible with roll-to-roll automated mass production.

Modular atomization combined with an integrated conveyor‑belt annealing design enables direct scaling to continuous roll‑to‑roll production, supporting large‑scale manufacturing on flexible PET and fabric substrates.

III. Key Technological Innovations of This Study

Innovation 1: VMA Vibration Mesh + Slit-Nozzle Composite Atomization Architecture

Innovation 2: A Low-Vapor-Pressure Green Solvent–Compatible Atomization System

Innovation 3: Directional Liquid Flow–Induced Preferential Molecular Alignment

Innovation 4: A Three-Layer, All-Aerosol Ink Solution

Innovation 5: Micro-Automatic Closed-Loop Production Line Design

IV. Existing Process Challenges and Corresponding Solutions for Overcoming Them

Challenge 1: Conventional atomized droplets are large, and the solvent evaporates rapidly, leading to severe coffee-ring effects.

Challenge 2: Halogenated solvents are highly toxic, and high-volatility solvents lead to poor crystallization of thin films.

Challenge 3: Conventional aerosol devices consume large amounts of ink, and the cost of expensive photovoltaic materials is excessively high.

Challenge 4: Multi-layer printed interfaces are prone to pinholes and increased series resistance.

Challenge 5: The fill factor significantly degrades over large print areas.

V. Future Diverse Application Scenarios

1. Large-area flexible photovoltaic modules

2. Wearable Fabric Solar Energy

3. Lightweight, Portable Photovoltaic Products

4. Low-Cost Power Supply for IoT Sensors

5. Upgrading Industrialized Green Printing Production Lines

Figure 1. (a) Schematic of the aerosol‑printing production line: three vibrating mesh atomizers (VMA) are used to print the hole‑transport layer, the photoactive layer, and the electron‑transport layer, respectively; a heating chamber is employed for annealing the hole‑transport and active layers. (b) Schematic of the vibrating mesh atomizer structure. (c) SEM image of the VMA showing hundreds of micropores distributed across its surface. (d) Droplet size distribution generated by the VMA. (e) Device architecture and the chemical structures of PTQ10 and Y6‑BO.

Figure 2. (a) Schematic of VMA operation in the uninstalled state, showing fine mist‑like atomization. (b) Translucent side view of the VMA, featuring a gas chamber and slit nozzle. (c) The printing nozzle in actual operation, with the aerosol region illuminated by a green laser beam. The solution flow rate is Ql = 100 mL·min⁻¹, and the carrier gas (N₂) flow rate is Qgas = 2 L·min⁻¹. (d) Plot of the Stokes number Stk as a function of the carrier gas flow rate Qgas. (e) Variation of the dry film thickness of the PTQ10:Y6-BO solution in an O‑XY medium (concentration 8 mg·mL⁻¹) with respect to the solution flow rate Ql and the printing speed V.

Figure 3. The leveling process of liquid films. (a) Schematic illustration of a wavy liquid film with wavelength λ. (b) Relationship between the leveling time of a liquid film and its wavelength. (c) Wavelength measured immediately after film printing (printing parameters: Ql = 100 mL·min⁻¹, Qgas = 2 L·min⁻¹, V = 3 mm·s⁻¹, T = 27°C, U = 3.03 m·s⁻¹, Stk = 0.46). (d) Photograph of the dried film showing uniform and smooth overall thickness (ITO glass size: 15 mm × 20 mm).

Figure 4. Morphological characteristics of PTQ10:Y6-BO thin films prepared by aerosol printing and spin coating (using CF as the solvent): (a) Atomic force microscopy surface topography image (area: 5 × 5 mm²), (b) Transmission electron microscopy image, (c) Two-dimensional GISAXS pattern, (d) Two-dimensional GIWAXS distribution map, (e) One-dimensional GISAXS fitting curve along the qxy axis, (f) GIWAXS line‑cut profiles of PTQ10:Y6-BO thin films fabricated by aerosol printing and spin coating, (g) UV–vis absorption spectrum of PTQ10:Y6-BO.

Figure 5. (a) J–V curves under AM 1.5G, 100 mW·cm⁻² illumination; (b) EQE curves; (c) carrier mobility; (d) Jph–Veff curves; (e) Jsc–Plight curves; and (f) Voc–Plight curves for aerosol‑printed samples and reference OSCs.

Table 1 Photovoltaic Performance of Aerosol-Printed Devices and Spin-Coated Reference Devices

Figure 6. Time-dependent evolution of the power conversion efficiency (PCE) as determined by J–V measurements for devices optimized using different droplet‑printing techniques. Symbols 12–18, 20–23, 27, and 55–75: hollow symbols indicate printing of the active layer alone; half‑filled symbols indicate simultaneous printing of the active layer and the HTL; solid symbols indicate simultaneous printing of the active layer, HTL, and ETL. *The ultrathin aerodynamic‑sprayed active layer is stacked on top of a thick ultrasonic‑sprayed active layer.