High-Efficiency, Phosphor-Free: Yellow LEDs Redefining Ultra-Warm Lighting (Low CCT)

High-Efficiency, Phosphor-Free: Yellow LEDs Redefining Ultra-Warm Lighting (Low CCT)

What just happened?

GaN-on-silicon (GaN-on-Si) LED technology is opening the door to a new generation of energy-efficient, phosphor-free light sources. This matters most in ultra-warm, low-CCT lighting—an area that has long forced the industry into a familiar compromise.

For years, yellow and ultra-warm LEDs typically meant one of two options: lower efficacy with stronger temperature sensitivity, or phosphor conversion with well-known drawbacks. Phosphor conversion can reduce colour purity, age over time, lower performance, and introduce colour shift (drift).

The new “phosphor-free” direction targets that trade-off directly, because the chip emits yellow light natively—rather than relying on “white LED + phosphor”.

A new benchmark for yellow LEDs

In 2018, Nanchang Silicon-Based Semiconductor Technology Co., Ltd. reported a major milestone: a yellow GaN-on-silicon LED chip that set a record in the yellow band.

• 318 lm/W at 565 nm
• wall-plug efficiency: 51.6%
• high colour purity and strong thermal stability

This is the key point: removing phosphor reduces a common aging mechanism, which can lower the risk of long-term colour drift and performance loss seen in phosphor-based solutions.

Compared to classic AlGaInP yellow LEDs (often used in signalling and indicators), the GaN-based chip shows a smaller temperature droop. In real luminaires—where heat, humidity, and non-lab conditions are normal—this translates into more predictable output over time.

What does it enable? Two major “phosphor-free” product directions

1) Multi-colour phosphor-free LEDs for human-centric lighting (education)

Where visual comfort and spectral control matter—such as classrooms—multi-colour systems enable dynamic spectrum tuning. This allows lighting to adapt to context: study, creative work, or calming modes.

A practical advantage is more precise spectral shaping, including the ability to reduce short-wavelength blue content when desired. This type of control can support visual comfort in learning environments.

Typical luminaire specs reported for “classroom” solutions include:

• 3000 lm at 36 W
• Ra > 90, R9 > 90
• tunable CCT: 2000K–5000K

2) “Golden Light LED” for roads, tunnels, and outdoor infrastructure

The second direction targets infrastructure. A yellow GaN chip is combined with efficient red LEDs to create a characteristic “golden” spectrum—still without phosphor.

Common performance targets include:

• very warm colour appearance: 1800–2200K
• Ra > 70 (often sufficient for roadway applications)
• high efficacy and robust operation in demanding environments

In practical streetlighting systems, figures up to 145 lm/W at 2000K are reported. Not long ago, that level of efficiency at such a low colour temperature was simply out of reach for typical solutions.

Why this matters (no fluff)

• No phosphor – fewer aging-prone elements and potentially lower colour drift risk.
• Higher yellow-band efficiency – real energy savings, especially in 24/7 infrastructure.
• Better thermal stability – fewer surprises after the source is enclosed in a luminaire.
• Spectral control – a tool to design lighting for people and for specific environments.

What does “phosphor-free” mean in practice?

It means the target colour is generated without phosphor conversion. The chip emits yellow light directly, which helps avoid typical phosphor aging issues and long-term colour shift.

Why has low-CCT been difficult to do efficiently?

Ultra-warm light has often required either reduced efficacy or phosphor-based conversion that can degrade over time. A phosphor-free approach reduces that compromise.

What is “temperature droop” and why does it matter?

It’s the drop in light output as temperature rises. Lower droop generally means more stable performance in real luminaires, where LEDs operate at elevated temperatures.

Where does “golden light” deliver the most value?

Roads, tunnels, and outdoor infrastructure benefit from warm colour, efficiency, and reliability. In 24/7 operation, improved efficacy and stability directly impact energy and maintenance costs.