I. Core Research Summary

• Layer-by-layer deposition still enables the formation of a vertically intermixed bulk heterojunction structure.

First, a dense Y12 acceptor film is prepared, followed by aerosol deposition of the PM6 donor. The tiny aerosol droplets penetrate the acceptor’s surface layer, spontaneously forming a uniform BHJ phase distribution rather than a rigid bilayer, thereby perfectly matching the charge-transport requirements of inverted n-i-p devices.

• Response surface methodology identifies the optimal aerosol process window.

Optimal parameters: carrier gas flow rate of 100 sccm, ultrasonic power of 0.475 A, and printing speed of 10 mm/s; the D/A ratio was precisely tuned to approximately 1:1.2. The optimal device exhibited an open-circuit voltage of 796 mV, a short-circuit current density of 24.20 mA/cm², and a fill factor of 55.4%, with a maximum power conversion efficiency (PCE) of 10.67%, representing a 14.8% improvement over one-step co‑blended aerosol‑based devices (9.29%).

• Multiple characterization techniques confirm uniform vertical phase separation.

FLAS deep spectroscopy, STEM‑EELS carbon/sulfur elemental mapping, and GIWAXS diffraction collectively demonstrate that aerosol‑induced donor penetration disrupts the long-range ordered structure of Y12, forming a nanoscale interpenetrating network that significantly enhances exciton dissociation and charge carrier transport.

• High-efficiency devices simultaneously exhibit long-term photostability.

After 1080 hours of continuous illumination under one standard solar irradiance, the power‑loss degradation of devices fabricated using the optimal processing conditions was significantly lower than that of the low‑efficiency control group, demonstrating that precisely engineered BHJ morphologies can simultaneously enhance both photovoltaic performance and resistance to light‑induced degradation.

• Maskless Digital Adjustable Deposition Scheme

The three key aerosol parameters allow independent control of film thickness and the D‑ratio, eliminating the need to reformulate the ink and enabling rapid iterative optimization of the active-layer morphology, thereby accommodating a wide range of organic photovoltaic material systems.

II. Complete OPV Preparation Process and Core Technological Advantages of Ultrasonic Aerosol Technology

(1) Complete Inverted Organic Photovoltaic Fabrication Process

• Ultrasonic cleaning of the ITO glass substrate, spin-coating of the ZnO electron transport layer, followed by annealing at 200°C;
• Spin-coat the Y12 acceptor solution, followed by a brief annealing at 120°C to form a dense interlayer.
• Optomec’s ultrasonic aerosol‑jet system atomizes PM6 donor ink—o‑xylene—and prints the donor thin film layer by layer according to a gradient‑based parameter set.
• Uniform active layer; 120°C annealing promotes phase separation.
• A MoO₃ hole-transport layer was deposited via thermal evaporation, followed by the deposition of an Ag top electrode; after encapsulation, a comprehensive suite of J‑V, morphological, and aging tests was performed.

(II) Five Major Process Advantages (Comparison of Spin Coating, Doctor Blade, and One-Step Inkjet)

• Precisely tune the D/A ratio layer by layer, addressing the persistent challenge of uncontrollable morphology in blended inks.

With one-step coating, the ink formulation is fixed, making it difficult to fine-tune the phase separation of the film layer; in contrast, aerosol‑based independent deposition of the donor material allows precise control of the donor content via printing parameters, easily achieving an optimal 1:1.2 ratio.

• Ultrafine droplets spontaneously form a BHJ without the need for complex additive engineering.

Aerosol‑derived micron‑scale droplets penetrate the underlying receptor layer, naturally forming a nano‑interpenetrating network, thereby eliminating the need for substantial interfacial‑modifying additives and reducing the risk of photodegradation in the thin film.

• Non-contact printing is compatible with large-area, curved flexible substrates.

Spin coating is limited to small‑size wafers, and the doctor blade can easily damage the underlying film; aerosol deposition offers a safe spray distance of 3–5 mm, making it well suited for future roll‑to‑roll continuous production of flexible photovoltaics.

• Rapid iterative parameter digitization and high-throughput process screening

The airflow, power, and speed—three variables—are independently adjustable, and when combined with a Box–Behnken statistical model, only 16 experimental runs are needed to optimize the entire parameter space, significantly boosting R&D efficiency.

• Green o‑xylene ink system, low‑pollution additive manufacturing

It employs an environmentally friendly o‑xylene solvent, avoids highly toxic halogenated reagents, reduces the cost of treating process waste streams, and meets the requirements of industrial-scale green production lines.

III. Five Key Technological Innovations

Innovation 1: A Novel Ultrasonic Aerosol Layer-by-Layer Deposition Process for BHJ Organic Photovoltaics

Innovation: A Quantitative Optimization Framework for Photovoltaic Processes Based on the Box–Behnken Response Surface Methodology

Innovative Three-Dimensional Multidimensional Thin-Film Morphology Joint Characterization Scheme

Innovation 4 Efficiency – A Synergistic Approach to Morphology Control for Enhanced Stability

Innovation 5: A Scalable All-Printed Organic Photovoltaic Manufacturing Route

IV. Existing Process Challenges and Corresponding Solutions for Overcoming Them

Challenge 1: The inverted OPV layer-by-layer fabrication process tends to form a pure bilayer film, resulting in low exciton dissociation efficiency.

Challenge 2: In one-step blending ink coating, the D/A ratio is fixed, leaving very limited room for morphology optimization.

Challenge 3: The traditional trial-and-error approach to process optimization requires large sample quantities and has long cycle times.

Challenge 4: Under prolonged illumination, highly active organic thin films are prone to phase-domain coarsening and a sharp drop in efficiency.

Challenge 5: Spin coating and blade coating cannot achieve large‑area, flexible roll‑to‑roll mass production.

V. Future Diversified Industrial Application Scenarios

1 Building-integrated semi-transparent photovoltaic curtain wall

2 Flexible, Portable Wearable Energy Devices

3 Low-Power Micro Power Supply for the Internet of Things

4. Vehicle-mounted curved photovoltaic skylight

5 High-Throughput Photovoltaic R&D Platform for Universities

Figure 1. Workflow for fabricating inverted‑structure organic photovoltaic devices by depositing donor materials using ultrasonic aerosol jet printing and employing a Box–Behnken experimental design.

Table 1. Aerosol Jet Printing Conditions for Depositing PM6 Solution in OPV Devices

Table 2. Ultrasonic AJP conditions for OPV devices and a description of the values required for depositing the donor material on the ITO/zinc oxide/Y12 stacked layer, with respect to each factor.

Table 3. Mean optical density (OD) intensities of donor and recipient peaks, along with their ratios per device.

Figure 2. Optical density (OD) or UV–vis absorption measurements of the OPV device’s active layer after printing the donor material via ultrasonic aerosol jet printing, corresponding to data obtained when screening (a) flow rate, (b) power, and (c) speed parameters.

Figure 3. Response surface methodology using a Box–Behnken experimental design with PCE as a control variable. Left: response surface plot; right: contour plot. The following three factors were screened: (a) flow rate and power, (b) flow rate and velocity, and (c) power and velocity, while holding the third factor at its respective mean level.

Table 4. Typical AJP Performance Statistics for BBD Central Point Devices

Table 5. Comparison of Average J–V Parameters: Hybrid Ink uAJP vs. Optimized Sequence uAJP

Figure 4. Thickness distribution profiles of the active layer. (a) In-situ optical absorption spectra as a function of wavelength for different film thicknesses during soft plasma etching. (b) Film‑thickness‑dependent absorption spectra (FLAS); (c) Depth‑resolved concentration (w/w) derived from the data in (a). For clarity, the spectra in (b) have been vertically realigned, with the top-to-bottom sequence representing the distribution from the MoOx/active‑layer interface (film thickness 0 nm) to the active‑layer/ZnO interface (film thickness 100 nm). (d) STEM‑EELS cross-sectional maps of carbon and sulfur in an inverted OPV device.

Figure 5. (a) A pristine Y12 film prepared by spin coating from o‑xylene; (b) a composite film formed by further depositing PM6 onto the Y12 film via aerosol jet printing; (c) a comparison of cross-sectional images in the in-plane (IP) and out-of-plane (OOP) directions for the two measurements. The peak positions of pure Y12 are indicated by vertical dashed lines (black: out-of-plane; red: in-plane). To clearly visualize the composite sample, all cross sections have been offset by the same scale factor.

Figure 6. Stability test of a reverse‑bias OPV device under single‑sunlight illumination with a white LED light source (duration: 1080 hours): J–V characteristics measured using the uAJP donor material before and after the test (measured under AM1.5G illumination on the LineOne instrument), showing (a) power conversion efficiency (PCE), (b) short‑circuit current density (Jsc), (c) open‑circuit voltage (Voc), and (d) fill factor (FF).