How Modern TVs Work — LED vs OLED vs QLED Technology Explained

Shop shelves are brimming with abbreviations: LED, OLED, QLED, Mini-LED, Neo QLED, QNED, NanoCell. Marketing departments are doing their job, but for the average buyer it becomes an impenetrable thicket. Yet understanding the technology helps not only in choosing a TV but also in maintaining it properly — different technologies age and fail differently.

At the SATER service centre, we've been repairing televisions across all technologies since 1993 — starting with CRT sets. Over 30+ years, we've watched generations change and know which faults are typical for each technology.

The Foundation: LCD Panel

Most modern televisions (apart from OLED) are built on liquid crystal technology — LCD (Liquid Crystal Display). The principle:

1. Light source (backlight) — LEDs positioned behind the panel or along its edges.
2. Polarising filters — two layers that only allow light through in a specific plane.
3. Liquid crystals — molecules that twist under an electric field, controlling how much light passes.
4. Colour filters — red, green, and blue sub-pixels create the full-colour image.

The LCD problem: liquid crystals cannot completely block backlight. So black on an LCD isn't true black — it's dark grey. This effect is called "backlight bleed."

LED — Types of Backlight

Edge-lit: LEDs along the panel's edges, light distributed via a light-guide plate. Thin housing (5-10 mm), but uneven brightness and visible edge bleed. Found in budget and mid-range Samsung, LG, Hisense.

Direct-lit: LEDs behind the entire panel surface. More uniform brightness but thicker housing. Found in budget TVs.

Full Array Local Dimming (FALD): Direct-lit with independently controlled dimming zones. Significantly better contrast. Found in mid-range and premium models.

Mini-LED: Evolution of FALD: thousands of tiny LEDs (0.2-0.5 mm diameter) create hundreds or thousands of dimming zones. Minimal haloing, excellent contrast, brightness up to 2000-4000 nits. Found in Samsung QN85-QN95 (Neo QLED), LG QNED Mini LED, Sony X95, TCL, Hisense.

OLED — Self-Emissive Pixels

OLED (Organic Light-Emitting Diode) is a fundamentally different technology. Each pixel is its own light source. No backlight needed.

How It Works

• Each pixel comprises organic (carbon-based) light-emitting layers.
• A pixel switches fully on or fully off — delivering absolute black (0 nits).
• Contrast ratio is infinite.
• Viewing angles are perfect.

OLED Types

WOLED (LG Display): White OLED + colour filters. Used in LG, Sony, Philips, Panasonic TVs. All OLED TV panels come from LG Display.

QD-OLED (Samsung Display): Blue OLED + quantum dots for green and red. Brighter, more saturated colour. Used in Samsung S95, Sony A95K/A95L.

OLED Ageing

OLED pixels degrade over time — the organic material loses efficiency. The blue sub-pixel degrades faster than red and green. This can lead to brightness unevenness, residual images (burn-in), and a warm colour shift.

Lifespan: with normal home use, modern OLED panels last 7-10+ years before noticeable degradation.

QLED — Quantum Dots

QLED (Quantum Dot LED) is Samsung's marketing term for LCD TVs with a quantum dot film.

• The base is a standard LCD panel with LED backlighting.
• Between the backlight and LCD panel sits a film of quantum dots — nanoparticles that, when hit by blue light, emit pure red or green light.
• Result: wider colour gamut, brighter and more saturated colours.

QLED is NOT OLED. It's an enhanced LCD. Don't confuse them.

Neo QLED is QLED + Mini-LED backlight. The best of both worlds.

Display Resolution

Do you need 8K? In 2026 — no. There's virtually no 8K content. 4K is the optimal choice.

Refresh Rate

• 60 Hz — standard for budget models. Sufficient for TV, films, YouTube.
• 120 Hz — for gaming consoles (PS5, Xbox Series X) and fast-paced sport. Smoother motion.
• 144 Hz — appearing in premium models. Advantage over 120 Hz is minimal for most viewers.

HDR Formats

• HDR10 — base format, supported by all 4K TVs. Static metadata.
• HDR10+ — dynamic metadata (settings change scene by scene). Supported by Samsung, Amazon Prime.
• Dolby Vision — dynamic metadata, up to 12-bit, up to 10,000 nits. Supported by LG, Sony, Netflix, Disney+.
• HLG (Hybrid Log-Gamma) — for broadcast TV. Backwards compatible with SDR TVs.

Processing Chips

The processor affects upscaling (enhancing lower resolution to 4K), motion handling, and HDR tone mapping:

• Samsung NQ8 Gen 3 AI — excellent upscaling and motion processing.
• LG Alpha 11 — AI upscaling, Dolby Vision processing.
• Sony XR — the best motion handling and colour naturalness.

All three are excellent processors. Differences are only visible in side-by-side comparison.

How Each Technology Fails

At the SATER service centre, we repair LED/LCD TVs at component level: LED strip replacement, power supply repair, T-Con board replacement, mainboard repair. Bring yours in — we'll diagnose it and give you an honest assessment of whether repair is worthwhile.