Introduction
As the world accelerates towards a clean energy transition, the solar photovoltaic (PV) industry continues to innovate, improving efficiency, durability, and cost-effectiveness. Among the most prominent solar cell technologies today are Mono PERC (Passivated Emitter and Rear Cell), TopCon (Tunnel Oxide Passivated Contact), and HJT (Heterojunction Technology). Each of these technologies presents unique advantages and challenges, influencing their adoption across different markets, especially in India.
This article delves into the technical, economic, and policy aspects of these technologies and their implications for the future of solar energy.
1. Understanding the Technologies
a. Mono PERC – The Established Workhorse
Mono PERC technology has dominated the solar industry due to its relatively low cost and higher efficiency (~22%) compared to older polycrystalline modules. It enhances traditional monocrystalline cells by adding a passivation layer at the rear, improving light absorption and reducing recombination losses.
✅ Advantages:
- Well-established manufacturing infrastructure.
- Lower production cost (~₹8.34/W in India).
- Readily available in both DCR (Domestic Content Requirement) and non-DCR versions.
⚠️ Challenges:
- Higher temperature coefficient (-0.35%/°C) makes it less efficient in extreme heat.
- LID (Light-Induced Degradation) and PID (Potential-Induced Degradation) impact long-term performance.
- Becoming outdated as newer technologies surpass it in efficiency.
b. TOPCon – The Next Evolutionary Step
TOPCon technology improves upon Mono PERC by introducing tunnel oxide and passivated contacts, enhancing carrier selectivity and reducing electron recombination. With efficiency reaching 23-24%, it offers a compelling alternative to PERC.
✅ Advantages:
- Higher efficiency (~23-24%) with minimal modification to existing PERC lines.
- Lower LID and PID impact, ensuring longevity.
- Better bifacial gains (70-80%) for dual-side energy generation.
⚠️ Challenges:
- Requires moderate production line upgrades (~$40M/GW investment).
- Higher defect rates in soldering and lamination, increasing rework needs.
- Slightly more sensitive to impurities, requiring cleaner production environments.
📌 India’s ALMM (Approved List of Models and Manufacturers) has started including TOPCon, with nearly 11% of the country’s PV capacity transitioning to this technology.
c. HJT – The Future of High-Efficiency Solar Cells
Heterojunction Technology (HJT) combines crystalline silicon (c-Si) with amorphous silicon (a-Si) layers, reducing recombination losses and enabling efficiencies of 24-26%. It offers superior temperature performance (-0.25%/°C), making it ideal for hot climates like India.
✅ Advantages:
- Highest efficiency potential (~26%) among commercial technologies.
- Lower degradation rates with minimal LID and PID impact.
- Excellent bifacial gain (>90%), maximizing energy yield.
⚠️ Challenges:
- Requires completely new manufacturing lines (~$70M/GW investment).
- High silver consumption (~120-140 mg/cell), increasing material costs.
- More complex interconnection and soldering processes, necessitating advanced O&M strategies.
📌 Despite its potential, HJT adoption in India is slow due to high production costs and limited local manufacturing capacity.
2. Policy & Market Considerations in India
India’s solar growth is shaped by policy frameworks, domestic manufacturing initiatives, and quality standards. Key policies affecting the transition from Mono PERC to TOPCon and HJT include:
📌 Domestic Content Requirement (DCR):
- From June 2026, all government-backed projects must use India-made cells.
- Higher production costs (~₹25/W for DCR modules vs. ₹15/W for non-DCR) impact project economics.
📌 Production-Linked Incentive (PLI) Scheme:
- Encourages high-efficiency module production (favoring TOPCon & HJT).
- Helps offset high CapEx costs for manufacturers upgrading to newer technologies.
📌 Basic Customs Duty (BCD):
- 40% duty on imported solar modules & 25% duty on cells promotes domestic manufacturing.
- Favors Mono PERC (already domestically produced) but creates short-term cost barriers for TOPCon & HJT, which rely on imports.
📌 Approved List of Models and Manufacturers (ALMM):
- Only approved manufacturers can participate in government projects.
- Encourages quality control but delays in listing newer technologies hinder adoption.
3. Maintenance & Operational Challenges
Transitioning from Mono PERC to advanced technologies like TOPCon and HJT requires changes in operations & maintenance (O&M) strategies.
📌 Key Takeaways:
- TOPCon requires additional PID monitoring & infrared inspections to detect soldering defects.
- HJT demands specialized cleaning methods & regular EL scanning to avoid microcracks.
4. Cost Analysis & Future Outlook
While Mono PERC remains dominant, TOPCon is emerging as the next big upgrade due to low transition costs. HJT, despite being the most efficient, needs government incentives & industry collaboration for large-scale adoption.
Conclusion: The Road Ahead for India's Solar Industry
India’s solar PV transition is at a critical juncture. While Mono PERC is still widely used, the push towards higher efficiency and long-term sustainability is driving interest in TOPCon and HJT. Government policies like DCR, ALMM, and PLI will play a crucial role in shaping future adoption.
For industry leaders and investors, TOPCon offers the best near-term opportunity with moderate production line upgrades and higher efficiency benefits. However, long-term competitiveness will depend on:
- Scaling HJT manufacturing.
- Reducing silver consumption.
- Optimizing production costs.
📌 India’s journey towards 100 GW+ solar capacity will be defined by:
- Technological advancements.
- Policy frameworks.
- Global competitiveness.
By staying ahead of these developments, businesses and policymakers can position India as a leader in the next generation of solar innovation.