Science

 

Using its TRUFLEX® organic semiconductor and dielectric inks, or liquid polymers, Smartkem has developed a complete six-layer transistor stack and fabrication process. Smartkem’s core chemistry enables its electronic polymers to be processed at temperatures as low as 80oC, which by electronic industry standards is very low. The inks are solution deposited, onto low-cost plastic or glass substrates.

Features

Low Process Temperature
Compatible with industry-standard manufacturing infrastructure
Compatible with all front plane technologies inc. MicroLED, EPD, LCD & OLED
Printable on low-cost plastics: flexible & lightweight

Breakthrough Technology

 

The TRUFLEX® materials stack is a breakthrough technology comprising six individually designed material formulations encompassing every layer in the device, starting from the initial planarising base layer, all the way through to the final passivation layer chemistry. The ink set includes the active organic semiconductor material and a series of orthogonal passive interlayer inks (Base layer, Self-Assembled Monolayer, Organic Gate Insulator, Sputter Resistant Layer and Passivation layer). Smartkem’s proprietary materials set is covered by an extensive IP portfolio comprising 125 granted patents across 19 patent families and 40 codified trade secrets.

Driver ICs

 

If you were to use a direct wiring PCB based approach, the number of tracks required to connect to the LEDs are vastly different to the active-matrix backplane. For instance, for 90,000 mini-LEDs, 180,000 connections plus many ICs would be required. Using a TFT array for the backlight will significantly lower the manufacturing cost.

Full TRUFLEX® Transistor Stack: 6 Layers

Base Layer (BL)

Planarises the selected substrate and its chemistry is designed to match the properties of the Carrier Injection Modification layer and the OSC ink, thereby delivering highly uniform OSC ink morphology even in large area deposition.

Passivation Layer (PL)

Highly crosslinked photopatternable layer, designed to impart chemical resistance and physical integrity to the underlying OTFT array.

Organic Semiconductor (OSC)

The OSC is the ‘engine’ of the transistor determining the charge mobility of the device. TRUFLEX® OSCs uniquely comprises a hybrid of a high mobility p-type polycrystalline small molecule co-formulated with patented amorphous semiconducting polymers.

Sputter Resistant Layer (SRL)

Photopatternable, highly cross-linked organic polymer layer that has been designed to contain no ionic dopants. Its function is to protect the organic gate insulator material from plasma-induced sputter damage during gate metal deposition. It enables deposition of a wide range of gate materials including Mo/Al/Mo.

Organic Gate Insulator (OGI)

Selection of the chemistry of the OGI material is key as it is the mobility-determining interface with the OSC. The permittivity of the OGI material determines carrier density in channel and influences device hysteresis.

Carrier Injection Modification Layer (SAM)

Self-assembled monolayer that modifies the work function and surface chemistry of the source/drain electrodes. Controls charge injection into OSC and can influence uniformity of the OSC layer.

TRUFLEX® Core Chemistry

1. High Mobility, Small molecule
  • Theoretical intrinsic mobility ≥ 20 cm2V-1s-1
2. Semiconducting polymer ‘controls’
  • Morphology of OSC layer
  • Phase segregation & uniformity of the polycrystalline small molecule
  • Viscosity of ink
3. Solvents
  • Solubilise small molecule and amorphous polymer binder
  • Modify surface tension of the TRUFLEX® inks.
  • Influence ink viscosity
  • Solvents for printing

TRUFLEX® Benefits

ParametersSmartkem OTFTa-SiIGZOLTPS
Current usageIn development (demonstrated in mini/micro-LED, LCD, OLED, sensor, logic circuit) LCD and rigid e-paperOLED TVMobile phone (OLED and some LCD)
Typical charge mobility in display pixel3 cm2/Vs0.5 cm2/Vs10 cm2/Vs50 cm2/Vs
Process temperature<150 C standard process
<80 C modified process
300 C320 C350 C
Substrate compatibilityWide range of plastics and glassGlassPl/GlassPl/Glass
Current driving stabilityVery GoodAverageVery GoodExcellent
Impact resistanceExcellentPoorPoorPoor
Bend radius0.5 mm4 mm2 mm2 mm in neutral plane
Manufacturing maturityPrototypeExcellentFairGood
Process costLowLowMedium/HighMedium

TRUFLEX® technology advantages for printing

 

Smartkem’s technical approach of combining a high mobility polycrystalline small molecule with a matched semiconducting binder enables a wide formulation latitude and a wide range of printing methods. Rheology control of the ink is achieved through design of the chemistry of the binder, molecular weight selection/control and solids loading of the binder in the ink Smartkem’s OSC materials are soluble in a range of low toxicity organic solvents enabling wide ink formulation latitude and providing for control of evaporation rate of a range of droplet sizes (tens of picolitres and below)