What is the Difference Between a LCD, TFT, IPS, LED and OLED?




In the market, there are a lot of confusions between LCD, TFT, IPS and OLED.  Of course, all of them are displays.

  • LCD stands for Liquid Crystal Displays (In market, LCD defaults to “Passive Matrix LCD”),
  • TFT stands for Thin Film Transistor (In market, TFT defaults to “Active-Matrix TN type TFT LCD), 
  • IPS stands for In-Plane Switching (In market, IPS defaults to “High End Full Color LCD),
  • LED stands for Light Emitting Diode (In market, LED TV actually is a TFT TV but with LED backlights. It is not LED displays!)
  • OLED stands for Organic Light Emitting Diode. It is a display but not an LCD shown above.



Introduction to LCDs

In market, LCD means passive matrix LCDs which increase TN (Twisted Nematic), STN (Super Twisted Nematic) , or FSTN (Film Compensated STN) LCD Displays. It is a kind of earliest and lowest cost display technology.  LCD screens are still found in the market of low cost watches, calculators, clocks, utility meters etc. because of its advantages of low cost, fast response time (speed), wide temperature range,  low power consumption, sunlight readable with transflective or reflective polarizers etc.  Most of them are monochrome LCD display and belong to passive-matrix LCDs.


Introduction to TFT

A TFT  display normally uses TN type LCD technology. TFT LCDs is also categorically referred to as active-matrix LCDs. It tells that these LCDs can hold back some pixels while using other pixels. So, the LCD will be using a very minimum amount of energy to function (actually to make the liquid crystal molecules between two electrodes twisting). TFT LCDs have capacitors and transistors. These are the two elements that play a key part in ensuring that the TFT display monitor functions by using a very small amount of energy without running out of operation.

Normally, we say TFT LCD panels or TFT screens, we mean they are TN (Twisted Nematic) Type TFT displays or TN panels, or TN screen technology. TFT is active-matrix LCDs, it a kind of LCD technologies.

TFT has wider viewing angles, better contrast ratio than TN displays. TFT display technologies have been widely used for computer monitors, laptops, medical monitors, industrial monitors, ATM, point of sales etc.


Introduction to IPS

Actually, IPS technology is a kind of TFT display with thin film transistors for individual pixels. But IPS displays have superior high contrast, wide viewing angle, color reproduction, image quality etc. IPS screens have been found in high end applications, like Apple iPhones, iPads, Samsung mobile phones, more expensive LCD monitors etc. 

Both TFT LCD displays and IPS LCD displays are active matrix displays, neither of them can produce color, there is a layer of RGB (red, green, blue) color filter in each LCD pixels to make LCD showing colors. If you use a magnifier to see your monitor, you will see RGB color. With switch on/off and different level of brightness RGB, we can get many colors. Neither of them can’t release color themselves, they have rely on extra light source in order to display. LED backlights are usually be together with them in the display modules as the light sources. Besides, both TFT screens and IPS screens are transmissive, it will need more power or more expensive than passive matrix LCD screens to be seen under sunlight.  IPS screens transmittance is lower than TFT screens, more power is needed for IPS LCD display.

Introduction to LED

Mentioned above, LCD displays can’t produce light itself. They need backlight together as a display units (display modules). Years ago, there were mainly 3 kinds of LCD backlights;  LED backlight, CCFL (Cold-Cathode Fluorescent Lamps) backlights and EL (Electroluminescent) backlights. They were competing each other. CCFL can be used for large display backlights but they contain some environment unfriendly material; EL can be used in very thin design but it needs over 100V AC to drive and brightness is low. Thanks for the rapid progress of LED material and manufacturing progress, we can get brighter and longer life time LED chips. Some TV manufacturers were proud to announce that their TV sets were LED but they were not. They were still TFT or IPS LCD BUT with LED Backlighting.



Introduction to OLED

OLED displays are an emissive display technology not belong to LCDs. Each dot that is illuminated on the display is creating a small, bright area of glowing phosphor. Their contrast is very high which make OLED used in very high-end applications. Some of the even high end TV and mobile phones use AMOLED ( Active Matrix Organic Light Emitting Diodes) Displays. The technology provides even better color reproduction, image quality, better color gamut, less power than LCD technology. Please note that OLED includes AMOLED and PMOLED (Passive Matrix Organic Light Emitting Diodes). What you need to choose is AMOLED for you TV and mobile phones instead of PMOLED. If you have more budget, you can have your display screen with touch screen, most of the touch nowadays uses PCAP (Projective Capacitive) touch panel. This kind of touch technology was first introduced by Steven Jobs in the first-generation iPhone.


LCD, TFT, IPS, LED and OLED can be confusion and belong to different technologies but they have more thing in common: All of them are Flat Panel Displays, which differential themselves from the bulky, heavy, old fashion, expensive CRT (Cathode-Ray Tube). Please see if you are old enough to even see the display as below.


Fig.1 A CRT Monitor, still remember?