As a new-type foreign trade service provider driven by technology transformation and export business, HiSiaddi has established a "1+2+3+4=1" service system and can supply PEDOT:PSS materials sourced directly from multiple well-known original manufacturers. Boasting strong R&D capabilities, HiSiaddi has repeatedly proposed PEDOT:PSS formulation optimization and application improvement solutions through technical cooperation with factories and precise market insight. Below is a consulting case of PEDOT:PSS formulation optimization by HiSiaddi.
Contact HiSiaddi customer service for more formulation optimization consulting services.
FinnFlex Display Oy, located in the science and innovation park of Helsinki, Finland, is a major Northern European manufacturer of mid-to-high-end flexible OLED and foldable screen conductive films. Its products are mass-supplied to Nokia automotive flexible displays and European medical flexible blood oxygen sensing films. The company long purchased inkjet/slot-die coating-specific PEDOT:PSS conductive slurry imported from Heraeus, with an annual customized PEDOT:PSS procurement volume of 41 tons. After multiple rounds of sample verification, the enterprise selected domestically customized conductive liquid, and the first batch of 18 tons of raw materials was delivered to its existing roll-to-roll slot-die coating line.
The client’s complete slurry ratio, baking temperature zones and coating line speed processes were filed with the Finnish Electronic Materials Research Institute. Restricted by product access regulations, the base solid content and total additive dosage of the main agent could not be drastically modified; only minor adjustments to additive ratios and production processes were permitted. Within 10 days of launch, mass production defects emerged continuously: frequent wire drawing and pinholes on wet coated films, excessive regional sheet resistance fluctuation on dry films, out-of-spec sheet resistance drift after 500 h aging at 85°C/85% RH, and poor cross-hatch adhesion of coatings on PET substrates. The product yield plummeted from 95.8% with imported materials to 62.3%, forcing two foldable screen conductive film production lines to reduce output. With downstream automotive screen delivery deadlines approaching, the client faced severe risk of breach-of-contract compensation.
Raw material manufacturers only controlled physical and chemical indicators at factory release and specialized in polymer synthesis, with zero expertise in downstream slot-die coating, low-temperature baking and post-coating aging terminal application processes. Finnish R&D engineers were only familiar with supporting parameters of European imported materials and lacked research on domestic PEDOT:PSS characteristics including residual PSS acid value, micro-powder agglomeration and solvent system properties. Two weeks of independent fine-tuning of dispersant dosage and baking temperatures failed to resolve defects, so the enterprise formally entrusted HiSiaddi’s technical team to conduct full-dimensional fault tracing and formula-process rectification.
Cooperating with a domestic CNAS-accredited third-party testing institute, HiSiaddi conducted comprehensive analysis on raw domestic PEDOT:PSS stock solution, defective slurry sampled from production lines and scrapped conductive films, covering solid content, viscosity, particle size distribution, free PSS content, acid value, surface tension, SEM micro-morphology and damp-heat stability. Combined with the client’s workshop temperature/humidity, batching environment and coating-baking parameters, three overlapping root causes of defects were identified: inherent physical and chemical differences in domestic slurry, mismatched original formulations calibrated for imported materials, and imbalance between workshop production conditions and slurry adaptability.
Domestic PEDOT:PSS contains 3.1% free sulfonic PSS (versus ≤1.7% for original Heraeus materials), resulting in a highly polar slurry system. Insufficient homogenization post-polymerization generated abundant nano-scale soft agglomerates. The client’s original dispersant dosage of 0.7% was calibrated for low-free-acid imported slurry and failed to fully encapsulate agglomerated particles. Post-ball-milling slurry exhibited uneven micro-dispersion, and agglomerates clogged coating dies during slot-die processing, creating wire drawing and pinpoint pinhole defects. Uneven dry film thickness further induced regional sheet resistance fluctuations.
Abundant hydrophilic sulfonic acid groups on excess free PSS rapidly absorb water vapor under 85°C high-humidity conditions, widening the spacing of conductive polymer chains and reducing carrier migration efficiency. Actual testing showed sheet resistance increased by 13.8% after 500 h damp-heat aging, far exceeding the client’s internal control threshold of ≤6%. The original small dosage of epoxy crosslinking additives was formulated for low-acid imported materials and failed to neutralize excess acidic groups, rendering the anti-damp-heat system ineffective.
The domestic slurry adopted low-cost alcohol ether co-solvents, resulting in a surface tension of 39.2 mN/m (versus 32.5 mN/m for imported materials). Poor wetting and spreading performance on conventional PET substrates without enhanced corona treatment weakened interfacial bonding between coatings and substrates, leading to widespread film peeling in cross-hatch tests post-curing.
The client’s batching workshop maintained a constant ambient humidity of 63%. The stronger hydrophilicity of domestic PEDOT:PSS caused continuous moisture absorption from air when raw materials were left open for long periods, gradually lowering the actual solid content of the slurry and altering rheological properties, which further amplified coating defects.
Rectification Strategy: Short-term on-site process optimization to rapidly reduce scrap rates; medium-term refined formula fine-tuning to adapt domestic raw materials; long-term reverse promotion of upstream manufacturers to optimize PEDOT:PSS synthesis processes to eliminate fundamental defects.
1. Install dehumidification units in the batching workshop to stabilize ambient humidity at 42%~47%. Complete slurry preparation within 24 hours of opening PEDOT:PSS raw material drums; seal remaining stock solutions and store under light-shielded low-temperature conditions to block moisture intrusion.
2. Add a pre-dispersion step to batching: Stir slurry slowly with 15% of the formulation solvent for 60 minutes in advance to pre-swell and break soft agglomerates before transferring to the main batching tank, reducing die clogging probability.
3. Add simple in-line low-temperature corona pre-treatment for PET substrates to temporarily boost substrate surface energy and improve coating wetting and adhesion. Post-implementation, production line yield rose from 62.3% to 79.5%, temporarily securing basic production capacity to fulfill order deadlines.
1. Optimize dispersion system: Maintain unchanged total dispersant dosage; replace single fatty alcohol dispersant with a compound system of modified phosphate ester + nonionic surfactant to enhance encapsulation capacity for polar PSS agglomerates. Micro-agglomeration in slurry was nearly eliminated, drastically reducing die clogging, wire drawing and pinholes.
2. Adjust crosslinking additive ratios: Modify the original epoxy crosslinker to silicone additive ratio from 7:1 to 5.5:2.5. Higher silicone additive content utilizes siloxane groups to neutralize partial free sulfonic acid and passivate hydrophilic groups, mitigating moisture absorption under damp-heat conditions.
3. Supplement trace co-solvents: Within the fixed total additive proportion, moderately increase the fraction of low-surface-tension isopropanol solvents to lower slurry surface tension to 33.1 mN/m, matching PET substrate wetting requirements and elevating cross-hatch adhesion to level 0 (compliant).
4. Optimize segmented baking curves: Abandon the original constant 110°C baking; adopt staged heating: 60°C low-temperature pre-baking for 3 min to slowly remove surface solvents → 95°C medium-temperature film formation → 110°C final curing, avoiding pinhole defects caused by rapid solvent volatilization. After formula optimization, small-batch trial production yielded a recovery of 92.1% product yield, with sheet resistance rising by only 5.2% after 500 h damp-heat aging, basically meeting the client’s internal control standards.
HiSiaddi coordinated with domestic slurry manufacturers to secure dedicated polymerization reactors and optimize product indicators at the source:
1. Adjust polymerization feeding ratios and post-production dialysis purification processes, extending ultrafiltration dialysis duration to reduce free PSS content from 3.1% to 1.65%, benchmarking imported material levels.
2. Add trace silane-modified monomers post-polymerization for in-situ passivation of partial hydrophilic sulfonic acid groups, lowering slurry water absorption at the molecular level.
3. Upgrade high-pressure nano-homogenization equipment for secondary circulating homogenization to break micro-agglomerates, and optimize compound co-solvent systems to stabilize finished product surface tension within the 32~34 mN/m range at factory release.
1. Pilot verification of modified materials: 500 kg of factory-optimized modified PEDOT:PSS stock solution was airfreighted to Finland for mass production testing, utilizing the optimized formula and coating processes. Conductive film yield reached 95.5%, with full indicators including damp-heat aging, transmittance and sheet resistance matching original Heraeus German products. The client issued a formal product qualification confirmation document.
2. Full-year order delivery in batches: The remaining 23 tons were scheduled for production across 5 batches. HiSiaddi provided full supporting services including EU REACH and SCIP registration, bilingual 16-section SDS, full RoHS test reports, light-shielded sealed IBC tank compliant packaging, and smooth customs clearance and warehousing for shipments from Shanghai Port to Helsinki Port. Localized procurement costs decreased by 35.3% versus imports, enabling the client to deliver automotive display orders on schedule without breach.
3. Deepened business expansion: The client renewed an annual long-term framework order of 47 tons of PEDOT:PSS the following year, and entrusted HiSiaddi with exclusive agency for domestic customization, supporting technical formulation and export compliance for inkjet low-viscosity PEDOT:PSS and high-impedance insulating modified PEDOT series. Building on this project, HiSiaddi successfully developed two leading Northern European flexible display clients in Sweden and Denmark.
Domestic PEDOT:PSS manufacturers focus on standardized large-batch polymerization mass production, with optimization targeted at low-end general touch markets and fixed production formulas. They lack terminal application R&D capabilities covering slot-die coating, flexible film formation and damp-heat aging. Formulas of mid-to-high-end European and American optoelectronic enterprises are filed with official authorities and cannot undergo major modifications; minor differences in free monomers, acid value and surface tension of domestic slurry can trigger cascading mass production defects across the entire process. Manufacturers can only adjust factory release indicators and fail to coordinate end clients for customized adaptive formula optimization.
Breaking the traditional pure supply-and-trade foreign trade model, HiSiaddi built a closed-loop full-chain technical service system covering defect testing & tracing, refined on-site formula fine-tuning, production line process adaptation rectification, reverse customized modification of upstream slurry and end-to-end export compliance. It bridges the technical information gap between domestic synthesis manufacturers and overseas terminal coating factories, and secures long-term procurement cooperation with mid-to-high-end overseas clients via actionable technical support.
Contact HiSiaddi customer service for more formulation optimization consulting services.
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