I. Abstract of the Paper’s Core Research

This study employs oxygen‑plasma‑treated nickel oxide (O₂‑Ni) as the bottom metal electrode and utilizes aerosol jet printing to precisely deposit PEDOT:PSS interlayers of varying thicknesses. The work function changes are quantitatively characterized using a Kelvin probe, and organic Schottky infrared detectors are fabricated to demonstrate the resulting performance enhancements. The key findings are as follows:

Nanoscale precision layer-by-layer deposition process

Optimized ultrasonic atomization aerosol parameters ensure a stable single‑pass film thickness of 25 nm. By employing one-, two-, or three‑pass printing, modified layers with thicknesses of 25 nm, 50 nm, and 75 nm can be fabricated, with linearly controllable thickness and nanometer‑level precision.

Continuously Tunable Electrode Work Function via Thickness Control

The work function of the bare O₂‑Ni electrode is 5.37 eV; as the PEDOT:PSS thickness increases, the work function continuously decreases: 25 nm (5.31 eV), 50 nm (5.27 eV), and 75 nm (5.14 eV), approaching the intrinsic work function of PEDOT:PSS, which is 5.1 eV, thereby enabling continuous tuning of the energy levels.

Interface barrier optimization leads to significant improvements in device electrical performance.

At 75 nm, the series resistance of the modified-layer device is reduced by an order of magnitude, dark leakage current is significantly suppressed, and rectification characteristics are markedly improved; under a −0.2 V bias, the photoresponse is three times higher than that of the unmodified device.

Aerosol multi-substrate and irregular-shape compatibility

The printing working distance is adjustable from 2 to 35 mm, enabling localized, zone‑specific coating on planar, curved, and micro‑patterned electrodes without causing short circuits between adjacent interdigitated electrodes.

Low-Consumable Micro-Printing System

Only 1 mL of diluted PEDOT:PSS ink is needed to prepare multiple sample sets, and site-specific deposition significantly reduces the waste of conductive polymer consumables.

II. Complete Process Flow for Aerosol-Modified Electrodes

1) A nickel metal film was deposited onto a glass substrate using evaporation through a mask, followed by 2-minute oxygen plasma treatment at 200 W, resulting in the formation of a nickel oxide layer on the surface.

2) Dilute commercial PEDOT:PSS stock solution with deionized water at a 2:1 ratio to formulate a 3.5 cP ink suitable for low-viscosity aerosol printing.

3) Optomec aerosol ultrasonic atomization system, carrier/protective gas flow rate 30 SCCM, nozzle diameter 300 μm, platform temperature maintained at 40°C;

4) The same nickel strip was divided into four regions, each of which was coated with a PEDOT:PSS thin film of 0, 25, 50, and 75 nm thickness, respectively.

5) Remove the solvent by vacuum drying at 65°C, then spin-coat the P3HT:PCBM organic active layer.

6) An aluminum top electrode was deposited via electron-beam evaporation, an infrared Schottky detector was assembled, and a full suite of Kelvin probe and I–V optoelectronic measurements was completed.

III. Five Core Process Advantages of Aerosol Jet Printing (Compared with Spin Coating and Vacuum Evaporation)

Nanometer-scale thickness, precisely and controllably applied layer by layer.

Single‑channel deposition with 25‑nm increments, eliminating the need for complex in‑vacuum thickness monitoring; work function can be tuned on demand, whereas spin coating cannot achieve zone‑specific thickness control.

Graphical editing of fixed-point partitions

Coating can be confined to designated electrode areas, enabling the fabrication of multi‑workfunction electrode arrays on a single substrate, whereas spin coating can only achieve uniform coverage over the entire surface.

Conformal Deposition of Curved and Textured Microelectrodes

2–35 mm adjustable spray distance over a wide range, enabling uniform coating on 3D-shaped and three-dimensional metal electrodes.

Low-viscosity ink is versatile, and even small amounts of consumables are sufficient for proofing.

0.5–20 cP low-viscosity conductive polymer ink ensures stable atomization, and milliliter-scale ink volumes enable the preparation of multiple sets of comparative samples.

Maskless digital direct writing simplifies device fabrication.

CAD‑based patterning of coating regions eliminates the need for photolithography and shadow masks, thereby shortening the device R&D iteration cycle.

IV. Five Core Technological Innovations of This Study

Innovation: A novel process for ultra-thin, uniform modification of aerosols at 25 nm, in a single channel.

Achieve layer-by-layer nanoscale thin-film deposition of aerosols and establish a quantitative correlation between the number of printing layers and the work function.

Innovative Integrated Preparation Scheme for Multi-Functional Electrodes with Two Partitioned Zones

A single substrate is used to simultaneously fabricate four electrodes with distinct work functions, and a single process sequence is employed to produce both the reference samples and the gradient‑structured specimens.

Innovation: A New Approach to Precise Control of Energy Levels at Organic Optoelectronic Interfaces

By continuously tuning the work function of metal electrodes via ultrathin conductive polymers, the hole-injection barrier is reduced, leading to a substantial decrease in contact resistance.

Innovative 4‑mm wide working‑distance custom‑shaped electrode adaptation and modification system

Breaking free from the planar constraints of spin coating, this approach offers a viable pathway for interface modification of three-dimensional, flexible optoelectronic microelectrodes.

Innovation: A Validation Framework for Enhancing the Performance of Low-Power Infrared Detectors

It is demonstrated that optimizing the work function can triple the light response, thereby highlighting the practical value of aerosol‑based interfacial modification in optoelectronic devices.

V. Current Industry Challenges and Corresponding Solutions

Challenge 1: Spin coating can only deposit a uniform film across the entire substrate and cannot achieve spatially localized tuning of the electrode work function.

✅ Aerosol-based localized printing allows independent control of the modification thickness for different electrodes on the same device, enabling tailored energy-level alignment.

Challenge 2: In conventional thin-film processes, thickness is difficult to control precisely, and the work function exhibits unpredictable variability.

✅ Single‑channel stability improved by 25 nm increments, with thickness and work function predictable in a linear fashion, and experimental reproducibility significantly enhanced.

Challenge 3: Curved and three-dimensional microelectrodes are difficult to uniformly functionalize, resulting in numerous interfacial defects.

✅ Non-contact aerosol beam with a long spray distance, compatible with various shaped electrodes, and causes no mechanical compression damage to thin films.

Challenge 4: Vacuum‑based modification equipment is expensive, resulting in high R&D costs for small‑batch production.

✅ Desktop‑level aerosol equipment can perform surface modification, with extremely low consumable usage and a significant reduction in sample preparation costs.

Challenge 5: The metal–organic interface exhibits a high barrier, leading to large device leakage current and poor photoelectric conversion.

✅ Precise control of PEDOT:PSS thickness matches the organic HOMO energy level, reducing the injection barrier and boosting light response by a factor of three.

VI. Future Diversified Industrial Application Scenarios

1 Flexible Organic Infrared Photodetector

Aerosol‑based localized modification of flexible PI‑substrate microelectrodes enables low dark current and high sensitivity for wearable infrared sensing.

2 Printed OLED Micro-Pixel Array

Pixel-by-pixel tuning of the anode work function, uniformizing luminance and reducing the device turn-on voltage.

3 Organic Thin-Film Solar Cells

Optimizing the energy-level alignment at the electrode interface enhances hole collection efficiency, thereby increasing the open-circuit voltage and the photoelectric conversion efficiency.

4 MEMS micro-optical sensing chips

Site-specific ultrathin modification of micrometer-scale interdigitated electrodes, and batch fabrication of miniature, low-power on-chip sensing elements.

5 High-Throughput R&D Platform of the Organic Electronics Laboratory

A single substrate is used to fabricate multi‑gradient work‑function electrodes, enabling rapid screening of the optimal interface‑matching configuration.

Image and Text Guide

Figure 1. Sample layout, Kelvin probe measurements, and Schottky photodetector structure.

Figure 2. Comparison of Schottky photodetector performance for four φm bottom electrodes (1070 nm IR LED, 7.5 mW, 0.05 Hz pulse)