Polyethyleneimine is a water-soluble cationic polymer rich in primary, secondary, and tertiary amines. Relying on its five core characteristics—high-density amine groups, strong chelating ability, tunable work function, n-type doping, and excellent interfacial adhesion—it is widely used in six major electronics sectors: semiconductor manufacturing, display devices, printed flexible electronics, lithium batteries, PCB/microelectronics cleaning, and sensors. The following details its mechanisms,applications:
Ⅰ.Semiconductor wafers and advanced processes (electronic-grade high-purity PEI, 14nm and below processes)
This is one of the most promising applications of polyethyleneimine PEI. For example, a Chinese research team precisely loaded PEI onto nanoporous materials, achieving adsorption saturation within 15 minutes. The newly designed adsorbent achieved an amine efficiency of 0.37 in simulated industrial waste gas (CO₂ concentration 10%), far exceeding conventional levels.
1. Photoresist Stripping/Cleaning Aid
Mechanism of Action: Protonated amine groups carry a strong positive charge, neutralizing the negatively charged groups of photoresist and photo-induced residues. Simultaneously, it chelates metal impurity ions such as Cu, Al, and Fe on the wafer surface, reducing wafer metal contamination (total metal ions can be controlled to <10 ppb).
Applications: Residual photoresist cleaning after dry etching, 3D NAND, advanced packaging, surface activation before wafer electroplating; used with stripping solutions to enhance residue removal and reduce wafer micro-defects.
Core Advantages: Low metal impurities, low surface tension, non-corrosive to silicon/silicon oxide substrates, suitable for ultra-narrow linewidth advanced processes.
2. Wafer Surface Activation and Bonding Aid
Before bonding silicon wafers and glass wafers, an ultra-thin PEI coating introduces amine-active sites into the substrate, significantly improving the adhesion of dielectric films, photoresist, and metal plating; used for temporary wafer bonding and chip packaging interface modification.
3.Semiconductor Wastewater Metal Capturing Agent Semiconductor
Production wastewater contains heavy metals such as copper, nickel, cobalt, and tin. PEI amine groups strongly chelate and capture heavy metal ions, causing flocculation and precipitation, meeting the environmental emission standards of wafer fabs. It is a specialized chelating flocculant for electronic wastewater.
II. OLED/Organic Photovoltaic OPV (Core Electron Injection Layer of Inverted Devices)
1. Inverted OLED Electron Transport/Injection Layer (Most Mature Commercial Application)
Mechanism: PEI amine groups donate electrons, reducing the work function of the metal oxide (ZnO, ITO) cathode, significantly reducing the electron injection barrier, while simultaneously blocking holes and inhibiting exciton quenching.
Applications: Printed flexible OLEDs, Mini/Micro LEDs, inverted polymer light-emitting diodes (PLEDs); replacing traditional hygroscopic Cs₂CO₃ and LiF, significantly improving device air stability.
Performance Improvement: Reduced driving voltage at the same brightness, current efficiency more than 60% higher than the cesium carbonate system, roll-to-roll printing fabrication, suitable for mass production of flexible screens. Zinc ion chelation modification of PEI (PEI-Zn) improves conductivity by three orders of magnitude, enabling ultra-high brightness OLEDs (>100,000 cd/m²).
2. Organic Solar Cell OPV Interface Modification Layer
Spin-coating an ultrathin PEI layer between the photoactive layer and Al/Ag/Au metal electrodes transforms the high work function metal into a highly efficient electron-collecting electrode, eliminating the need for reactive Ca electrodes. This improves the air stability and conversion efficiency of photovoltaic devices, making them suitable for printed photovoltaic modules.
III. Printed Electronics and Flexible Conductive Materials (Carbon-based, Metal Nanowire Doping/Modification)
1. Carbon Nanotubes and Graphene n-type Dopants
PEI is a classic water-soluble n-type dopant. The amine group transfers electrons to carbon materials, modulating the Fermi level and converting p-type carbon nanotubes/laser-induced graphene (LIG) into n-type conductive materials, nearly doubling the thin film conductivity.
End Products: Flexible thermoelectric films, wearable sensors, flexible conductive electrodes, graphene printed circuits.
2. Conductive Ink Adhesion Modifier (Silver Nanowires, Carbon Paste Ink)
PEI amine groups crosslink with the carboxyl groups/epoxy groups of ink resins, while simultaneously electrostatically adsorbing silver nanowires and carbon powder, improving the adhesion of inks to flexible PET and PI substrates and preventing the conductive layer from peeling off when bent; used in flexible FPCs, touch screen conductive circuits, and RFID printed antennas.
3. PEDOT:PSS Electrode Modification
PEI can dedope PEDOT:PSS, controlling the electrode work function to prepare transparent flexible electrodes suitable for optoelectronic devices, widely used in flexible sensors and electronic skin substrate electrodes.
IV. Lithium-ion Batteries / Lithium Metal Anodes (Interface Protection Layer, Separator Coating)
1. Artificial SEI Film Coating for Lithium Metal Anodes (Cured-edge High-Energy Battery Technology)
Fluorinated modified PEI (PEIF) coating on the lithium metal surface:
The nitrogen-rich framework possesses lithium affinity, guiding uniform lithium-ion deposition and inhibiting lithium dendrite formation;
The hydrophobic fluorine side chains isolate moisture, allowing batteries to be assembled in ordinary air environments, eliminating the need for costly drying rooms;
During cycling, a stable LiF solid electrolyte interface is generated, extending the cycle life of lithium metal batteries.
2. Lithium Battery Separator Modification Coating
PEI-coated polyolefin separator: Amine groups adsorb electrolyte anions, improving lithium-ion conductivity; simultaneously, they chelate trace transition metal ions in the electrolyte, preventing metal deposition that could puncture the separator, improving battery safety and cycle stability.
3. Solid Polymer Electrolyte Dopant
PEI, as a lithium salt complexing carrier, coordinates Li⁺ with its amine groups, improving the ionic conductivity of the solid electrolyte, making it suitable for solid-state batteries and micro-energy storage devices.
V. PCB, Microelectronics Packaging and Surface Treatment
PCB Copper Foil Surface Roughening/Adhesion Promoter
PEI adsorbs onto the copper foil surface, providing active binding sites for solder resist inks and dry film photoresists, solving the problem of ink peeling off fine lines; used in high-end HDI and flexible PCB production.
Electroplating Pre-Activation of Electronic Components
Before nickel, gold, and silver electroplating, PEI is applied in trace amounts to the substrate to improve the uniformity of the metal plating layer and eliminate pinholes and plating defects.
Chip Packaging Underlying Adhesion Coating
In advanced molding and thin-film packaging, polyethyleneimine modifies the silicon/epoxy resin interface, reducing the probability of delamination and warpage failure.
VI. Electronic Sensors, Thermoelectric, Flexible Microelectronic Devices
Flexible Thermoelectric Thin Films
PEI-doped single-walled carbon nanotubes are used to prepare air-stabilized n-type thermoelectric thin films for wearable body temperature power generation and self-powered sensors for the Internet of Things, significantly improving the power factor.
Gas/Ion Sensor Sensing Layer
Polyethyleneimine PEI, with its abundant amine groups, can specifically adsorb CO₂, formaldehyde, and heavy metal ions. Coated with quartz crystals and carbon nanotube electrodes, it can be used to fabricate highly sensitive electronic gas and ion detection sensors.
Field-Effect Transistor (OFET) Interface Modification
An ultrathin polyethyleneimine PEI layer at the gate dielectric/semiconductor interface of organic field-effect transistors (OFETs) modulates interface charge trapping, improves carrier mobility, and reduces device leakage current.
