Low‑Resistivity UV‑Cured Inkjet‑Printed Silver Gate Electrode: A Fast, Low‑Temperature, High‑Adhesion Approach

Abstract

Inkjet‑printed silver gate electrodes were fabricated using a UV‑curing method that delivers an exceptional electrical resistivity of 6.69 × 10⁻⁸ Ω·m. By systematically varying the UV curing time and the distance (D) between the sample and the UV lamp, we identified optimal conditions that minimize residual organics and maximize conductivity. The resulting films exhibit excellent adhesion to glass substrates, achieving a 4B rating per ASTM standards. This study demonstrates a scalable, low‑temperature route to high‑performance silver electrodes suitable for flexible and printed electronics.

Background

Inkjet printing has become a cornerstone of printed electronics, offering drop‑on‑demand patterning that reduces material waste and process steps. Its compatibility with low‑temperature manufacturing is critical for flexible devices, yet most literature relies on high‑temperature (>200 °C) thermal curing or energy‑intensive sintering methods. UV curing presents a rapid, low‑temperature alternative that can remove organic residues from silver nanoparticle inks without exceeding 140 °C, making it attractive for temperature‑sensitive substrates.

Methods

Glass substrates were ultrasonically cleaned in isopropyl alcohol, tetrahydrofuran, deionized water, and a final IPA rinse. Silver nanoparticle ink (DGP‑40LT‑15C, Advanced Nano Products) was deposited using a Dimatix DMP‑2800 printer (10 pL cartridge) at 30 °C with a 35 µm drop spacing. UV curing was performed with an IntelliRay UV0832 system (600 W lamp). The distance D ranged from 37 cm to 23 cm, and curing times varied from 180 s to 480 s. For comparison, films were also heat‑treated in air at 25 °C–140 °C for 30 min.

Electrical resistivity was calculated from ρ = R_s × h, where R_s was measured with a four‑probe tester (KDY‑1) and h was obtained via a Dektak step profiler. Morphology and elemental composition were examined by SEM (NOVA NANOSEM 430) with EDS, and 3D surface topography was captured by a Veeco NT 9300 optical profiler.

Experimental Principle

UV radiation intensity diminishes with increasing D due to ozone absorption and scattering, reducing the energy delivered to the silver film. Ozone can oxidize silver, raising resistivity, while UV‑induced heating facilitates the removal of organics. Thus, both the curing depth (influenced by D) and the curing duration govern the final electrical performance.

Results and Discussion

Increasing UV curing time at D = 37 cm reduced resistivity sharply up to 360 s, beyond which the benefit plateaued, indicating near‑complete removal of organics. Elemental analysis confirmed decreasing carbon and oxygen contents with longer curing, while silver content rose.

Reducing D from 37 cm to 25 cm at a fixed 180 s curing time further lowered resistivity, as stronger UV exposure enhanced curing depth and organic removal. However, at D < 25 cm, resistivity rose again, likely due to silver oxidation (amorphous Ag₂O formation) and loss of conductive carbon bridging nanoparticles.

SEM and 3D profilometry revealed uniformly dispersed, non‑aggregated silver nanoparticles across all UV‑cured samples, with minimal surface roughness. Heat‑treated films, in contrast, showed particle coalescence and higher surface roughness, correlating with higher resistivity.

The optimal UV condition—D = 25 cm, 480 s—yielded a resistivity of 6.69 × 10⁻⁸ Ω·m and a 4B adhesion rating. Compared to heat‑treated films (resistivity ~3.68 × 10⁻⁸ Ω·m at 120 °C), UV curing delivers comparable performance with lower temperature and shorter processing time.

Conclusions

UV‑curing is an effective, low‑temperature strategy for fabricating inkjet‑printed silver gate electrodes with low resistivity and strong adhesion. Systematic control of curing time and distance allows optimization of organic removal and minimization of oxidation, resulting in electrodes suitable for high‑performance, flexible printed electronics.