Summary Table: Technologies at a Glance

Feature	TOPCon (Tunnel Oxide Passivated Contact)	PERC (Passivated Emitter & Rear Cell)	HJT (Heterojunction Technology)	Perovskite-silicon tandem	CdTe / CIGS (thin-film technologies)
Concept	– Ultra-thin silicon oxide “tunnel” layer added to crystalline solar cell	– Rear passivation layer added to standard crystalline silicon cell	– Crystalline + amorphous silicon layers	– Perovskite on top of silicon; each layer absorbs different light waves	– Non-silicon semiconductor thin layers
Typical efficiency	24–26% and improving¹	22–23%¹	24–26%¹	~27%² or ~34% (in labs)³	18-22% for CdTE⁴ ~25% for CIGS⁵
Temperature coefficient (how much efficiency is lost on hot days)	≈ –0.30%/°C (better in cold climates)¹	≈ –0.34%/°C (weaker)¹	≈ –0.26%/°C (best)¹	Varies²	≈ –0.3%/°C³
Low-light performance	⭐⭐⭐⭐	⭐⭐⭐	⭐⭐⭐⭐⭐	⭐⭐⭐⭐	⭐⭐⭐⭐
Annual degradation	0.3–0.4%	0.5–0.7%	0.25–0.35%	Being studied	1.5–2%
Manufacturing cost	Medium ⭐⭐⭐⭐	Lowest ⭐⭐⭐⭐⭐	Highest ⭐⭐	High ⭐⭐⭐	Medium ⭐⭐⭐⭐
Bifacial (double-sided) gain	80-85%	70%	90-95%	Unknown	Low but relatively good for diffuse light
Commercial maturity	Rapidly scaling, becoming mainstream	Mature, declining	Growing, premium niche	At early stage; limited supply	Mature; widely deployed, reliable.
Best suited for	High-efficiency, low-light, cold-climate, commercial and rooftop¹	Non-extreme temperature. Low budget deployments but large-scale is cost-sensitive¹	Ultra-high-efficiency premium markets¹	Large installation, but non-linear relationship with temperature⁸	Good in diffuse light (but not as good as the best silicon and tandem cells)⁴

Detailed Comparison

1. Efficiency

This is the percentage of sunlight converted to electricity under standard testing conditions, which is room temperature, meaning 25°C.

🔋 TOPCon

Doped polycrystalline silicon contacts reduce recombination losses
Typically 2–3% more efficient than PERC
Similar to HJT in many models and easier to produce
Excellent passivation and bifacial gains, especially on snow-covered ground
21.5%–23.2% at module level currently (for 2025 products)¹

🔋 PERC

For years the global standard, but hitting efficiency limits
While mature, the technology has been superseded and is being phased out by most large manufacturers
20.5%–22% at module level, widely deployed¹

🔋 HJT

Highest contemporary commercial efficiency; like TOPCon (but harder to manufacture)
Very low defect density because of amorphous silicon layers
Very good surface passivation and low recombination
But expensive to produce, as materials-intensive and process-sensitive
21.5%–23.5% at module level; some premium modules exceed 24%¹

🔋 Perovskite-silicon tandem

Two stacked solar cells: perovskite on top of silicon
Each layer uses different parts of the light spectrum
Commercial module prototypes ~27 %+ in scale-up projects²
Lab cells up to ~33.9%³

🔋 CdTe / CIGS

Absorbs light efficiently, using less material
Has a simple structure but chemically complex
18%–22% for CdTe⁴
24.6% for CIGS⁵

A quick addendum about further variations:

🔋 Perovskite–CIGS tandem
• Recently achieved ~23.6% (flexible) and ~29.36% (4-terminal)⁶

🔋 Perovskite–CdSeTe tandem
• Simulated potential ~40% theoretical efficiency; research ongoing⁷

Winner: HJT, but TOPCon is extremely close with far better cost-performance.

2. Loss of Efficiency with Temperature Rise

Solar panels lose efficiency as temperature rises (expressed as a temperature coefficient) making all solar photovoltaics more suitable for colder climates (during long Summer days).

The below figures show how much output falls as module temperature increases above 25°C.

🌡️ TOPCon

~–0.30%/°C¹
Strong performance on cold sunny days
Low losses in summer
Strong thermal resilience and loss caused by heat can self-recover

🌡️ PERC

–0.34%/°C¹
Drops off more quickly in heat
Less efficient in northern cold-climate winters than TOPCon

🌡️ HJT

~–0.26%/°C¹
Best of all three
Designed for heat-sensitive, high-efficiency installations

🌡️ Perovskite-silicon tandem

Temperature coefficient behaviour can be complex; standard metrics may not reflect real outdoor operation due to spectral and sub-cell interactions⁸
Performance in cold climates still unproven
Sensitive to heat and moisture

🌡️ CdTe / CIGS

Good thermal stability
Thin films often have lower temperature coefficients (~–0.3 %/°C) than crystalline silicon⁴

Winner for winter climates: HJT, with TOPCon extremely close and much cheaper.

3. Low-Light & Diffuse-Light Performance

Big factor for cloudy maritime climates (UK, Ireland, Norway, West Canada coast in particular).

☁️ TOPCon

Very good low-light sensitivity
Generates noticeably more energy on grey days than PERC
Ideal for cloud-heavy regions

☁️ PERC

The technology improves light capture as well as reducing rear-side recombination
Still weaker than TOPCon & HJT
Loses proportionally more output in diffuse light

☁️ HJT

Excellent — best spectral response
Strong performance in low light and short winter days
Best annual yield for diffuse light

☁️ Perovskite-silicon tandem

Potentially highest output per area
Exceptional in diffuse light

☁️ CdTe / CIGS

Very good in diffuse light and often outperforms silicon in cloudy conditions
However, efficiency is lower than state-of-the-art silicon and tandem cells

Winner: HJT, but TOPCon is close and cheaper.

4. Degradation & Long-Term Reliability

🛡️ TOPCon

0.35%–0.45%/year after first year; field tests show some models with very low degradation over 3 years¹
Lower light-induced degradation (LID) than PERC. n-type silicon reduces it¹
Slower long-term ageing

🛡️ PERC

0.45%–0.55%/year typical; first-year losses ~2%¹
Higher susceptibility to LID and LeTID

🛡️ HJT

0.25%–0.35%/year; very low light-induced degradation¹

🛡️ Perovskite-silicon tandem

Stability is a the barrier to mass deployment; still being studied, but improving rapidly⁸

🛡️ CdTe / CIGS

1.5-2%⁹
Performance varies by manufacturer
Commercial thin films show long lifetimes

Winner: HJT, but TOPCon is significantly better than PERC.

5. Manufacturing and Scalability

⚙️TOPCon

Uses modified PERC production lines, plus silicon¹
Much cheaper to scale than HJT
Expected to dominate the market through 2030

⚙️PERC

Simplest crystalline silicon technology¹
Cheapest to make
But being replaced due to lower performance and ageing issues

⚙️HJT

Requires completely different machinery and complex processing¹
Uses silver on both sides and amorphous silicon layers
High CAPEX, higher price per watt

⚙️Perovskite-Silicon tandem

Add perovskite to layer to silicon.
Can be tuned to use specific light frequencies; using more of the spectrum.³
Scaling challenges remain such as uniformity, stability and yield

⚙️CdTe / CIGS

Requires less energy and fewer raw materials to produce⁴
CdTe is highly scalable
A few firms dominate CdTe manufacturing
CIGS is more fragmented and harder to scale

Winner: TOPCon (best price-performance),
PERC is cheaper but declining,
HJT is premium and expensive.

Best Choice for Canada & Northern Europe

Canada, Sweden, Britain: TOPCon

Best for most northern sites due to:

strong low-light response
excellent cold-weather performance
high efficiency for rooftop-constrained buildings
best overall cost-performance ratio

TOPCon is currently the sweet spot for cold, cloudy northern climates.

Canada, Denmark: PERC

Still viable for large-scale, low-cost projects
Best where land is abundant and cost-per-watt matters more than maximum yield
Less ideal for premium or winter-optimised installations

Finland, Norway, Switzerland: HJT

Optimal for the highest-yield rooftops
Excellent for winter solar farms where low temperatures boost performance
Best-in-class option where budget is flexible

Final Verdict

🌟 TOPCon = Best all-rounder

High efficiency, strong winter performance, affordable — ideal for northern regions.

💸 PERC = Budget option

Cheap and proven, but ageing and falling behind technically.

🚀 HJT = Premium high-performance

Highest efficiency and lowest losses, but higher cost slows adoption.

References

Ultimate Guide to PERC, TOPCon, and HJT Modules for 2025, Anern, 2025-08-26
Qcells says technology breakthrough could reduce space needed for solar panels, Reuters, 2024-12-18
Perovskite Tandem Solar Cells, Ossila
CdTe vs. CIGS Solar Panels: Differences, Performance & Applications, Terli, 2025-07-24
New record for CIGS perovskite tandem solar cells, Science Daily, 2025-02-04
Flexible_perovskite/CIGS_tech_reaches_23.64%_efficiency, Compound Semiconductor, 2025-04-10
Four-Terminal Perovskite-CdSeTe Tandem Solar Cells: From 25% toward 30% Power Conversion Efficiency and Beyond, Wiley, 2024-05-07
Researchers find that temperature coefficient may not a proper metric for perovskite/silicon tandem solar cells, Perovskite-info, 2023-07-22
Renewable and Sustainable Energy Reviews Determinants of the long-term degradation rate of photovoltaic modules: A meta-analysis, Renewable and Sustainable Energy Reviews Volume 216, 2025-07