TFTs

Thin-film transistors, or TFTs, are transistors fabricated in thin films, commonly used as the switching elements in the backplanes of displays. In active-matrix liquid crystal displays (LCDs) and other flat-panel technologies, each pixel is controlled by an individual TFT together with a storage capacitor, enabling precise voltage control, rapid refresh, and reduced cross-talk compared to older passive-matrix designs.

A TFT backplane consists of a grid of gate lines and data lines on a substrate, with a thin-film semiconductor channel between a source and a drain. When the gate voltage is applied, the transistor turns on and allows the data signal to charge the pixel capacitor. The stored voltage then modulates the liquid crystal orientation or drives the emissive element in OLEDs, preserving the image between refresh cycles.

Materials and device physics vary by technology. Amorphous silicon (a-Si) TFTs are inexpensive and robust but have lower carrier mobility, limiting refresh rates and high-resolution performance. Polycrystalline silicon (poly-Si) and low-temperature poly-Si (LTPS) offer higher mobility for higher resolution and faster response. Indium gallium zinc oxide (IGZO) has emerged as a popular alternative, combining good mobility with low leakage, enabling high-resolution displays with lower power consumption.

Manufacturing involves thin-film deposition, photolithography, and annealing on glass or flexible substrates. TFT technology underpins most modern LCDs and is increasingly used in OLED and other flat-panel displays due to improved control, brightness, and energy efficiency.