Lighting and displays: Engineering methods

Filament, gas, chip, laser or pixel: how each one glows

What this tab covers The engineering methods that can do this conversion, compared on efficiency, scale, economics, limitations and reliability.

Electric light comes from hot filaments, gas discharges, semiconductors (LEDs and laser diodes) and organic emitters; screens add filters or self-lit pixels.

Comparison

Method	Efficiency	Scale	Economics	Limitations	Reliability
LEDs¹	About 100 lm/W average sold, over 200 lm/W premium, up to 230 lm/W best	Indicator lights to stadium floodlights	Lowest cost of light; now the majority of sales in most regions (over 85% in China, over 75% in India)	Driver quality, glare, colour quality at the cheap end	Early LEDs last 10-15 years; drivers often fail first
Fluorescent and gas-discharge lamps¹¹⁵¹⁶	Compact fluorescent about 50-67 lm/W; linear fluorescent systems up to 108 lm/W	Offices, streets, warehouses	Being phased out	Contain mercury, controlled under the Minamata Convention (more than 150 Parties)	Ballasts and electrodes wear out
Incandescent and halogen¹¹⁵	Halogen about 20 lm/W; plain incandescent about 16 lm/W	Being pushed out by minimum performance standards, which cover about 110 countries	Cheap to buy, expensive to run	Most energy leaves as infrared heat	Short life
Lasers⁶¹³¹⁴	Fibre lasers up to about 40% wall-plug, about 50% best (company claims)	Milliwatts to tens of kW; IPG's high-efficiency range covers 4-30 kW	Valued for precision rather than light per watt	Cooling, eye safety	Long-lived pump diodes
LCD screens⁹	Most backlight is absorbed by polarisers and filters (no single figure found)	Phones to large TVs; BOE ships 37.1% of large LCD panels (2025 forecast)	Cheapest display per area	Backlight always on, lower contrast	Long life
OLED screens and panels³⁹	Commercial OLED lighting panels about 90 lm/W (2020)	Phones, TVs; Samsung Display ships 54.3% of large OLED panels and EDO 13.9% (2025 forecast)	Costlier than LCD	Blue emitters age fastest	Burn-in risk

LEDs beat every older lamp on efficacy, lifetime and controllability, which is why standards are removing incandescent, halogen and mercury lamps. The remaining gains are from about 100 lm/W average towards the 250 lm/W practical limit, better drivers, and controls that switch light off when not needed. For screens, OLED wins on dark content and LCD on cost per area.

How each method works

LEDs

A blue InGaN chip with a phosphor coating gives white light directly from electrical current; drivers convert mains AC to DC.

Fluorescent and gas-discharge lamps

Current through mercury vapour emits ultraviolet, which a phosphor coating turns into visible light; high-intensity discharge lamps (sodium, metal halide) use a hot arc.

Incandescent and halogen

A tungsten filament is heated white-hot; halogen gas lets it run hotter and last longer.

Lasers

Stimulated emission in a semiconductor or doped fibre gives a coherent beam; used for cutting, welding, communications and some projectors.

LCD screens

An LED backlight shines through a polariser, a liquid-crystal layer that twists light per pixel, and colour filters.

OLED screens and panels

Thin organic layers in each pixel emit light when current flows, so black pixels use no power.

Sources

The next wave of LED lighting: smarter, circular and more efficient (commentary) International Energy Agency, 2026
2019 Lighting R&D Opportunities US Department of Energy, Solid-State Lighting Program, 2020
High efficiency fiber lasers (YLS-ECO series) IPG Photonics, 2026
Omdia forecasts large-area display shipments to grow 2.8% YoY in 2025 (press release, 3 October 2025) Omdia, 2025
IPG Photonics Form 10-K for fiscal year 2025 IPG Photonics / US SEC, 2026
Laser technology in transition: moderate growth in the laser market (AKL'26 press release, 30 June 2026) Fraunhofer ILT, 2026
LED bulb efficiency expected to continue improving as cost declines (Today in Energy, 19 March 2014) US Energy Information Administration, 2014
Energy Savings Forecast of Solid-State Lighting in General Illumination Applications (2019) US Department of Energy, 2019