Advancements in Solar PV Technologies: A Deep Dive into Mono PERC, TopCon, and HJT

The Evolution of Solar PV Technologies: Mono PERC, TopCon, and HJT – A Comprehensive Analysis

Introduction

As the world accelerates toward a clean energy transition, the solar photovoltaic (PV) industry is continually innovating to enhance efficiency, durability, and cost-effectiveness. Among the leading solar cell technologies are Mono PERC (Passivated Emitter and Rear Cell), TopCon (Tunnel Oxide Passivated Contact), and HJT (Heterojunction Technology). Each of these technologies offers distinct advantages and challenges, affecting their adoption in various markets, particularly in India. This article examines 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 been a leader in the solar industry due to its relatively low cost and higher efficiency (approximately 22%) compared to older polycrystalline modules. It enhances traditional monocrystalline cells by incorporating a passivation layer at the rear, which improves light absorption and reduces recombination losses.

• Advantages:
  • Well-established manufacturing infrastructure.
  • Lower production cost (approximately ₹8.34/W in India).
  • Available in both DCR (Domestic Content Requirement) and non-DCR versions.
• Challenges:
  • A higher temperature coefficient (-0.35%/°C) makes it less efficient in extreme heat.
  • Light-Induced Degradation (LID) and Potential-Induced Degradation (PID) can affect long-term performance.
  • It is becoming outdated as newer technologies surpass it in efficiency.

b. TOPCon – The Next Evolutionary Step

TOPCon technology builds on Mono PERC by introducing tunnel oxide and passivated contacts, which enhance carrier selectivity and diminish electron recombination. With efficiencies reaching 23-24%, it presents a compelling alternative to PERC.

• Advantages:
  • Higher efficiency (23-24%) with minimal modifications to existing PERC production lines.
  • Lower impact from LID and PID, ensuring longevity.
  • Improved bifacial gains (70-80%) for dual-side energy generation.
• Challenges:
  • Requires moderate production line upgrades (approximately $40M/GW investment).
  • Higher defect rates in soldering and lamination, increasing rework needs.
  • Slightly more sensitive to impurities, necessitating 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 shifting 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 achieving efficiencies of 24-26%. It boasts superior temperature performance (-0.25%/°C), making it particularly suitable for hot climates like India.

• Advantages:
  • Highest efficiency potential (up to 26%) among commercial technologies.
  • Lower degradation rates with minimal LID and PID impact.
  • Excellent bifacial gain (>90%), maximizing energy yield.
• Challenges:
  • Requires entirely new manufacturing lines (approximately $70M/GW investment).
  • High silver consumption (120-140 mg/cell), increasing material costs.
  • More complex interconnection and soldering processes, which demand advanced operations and maintenance 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 influenced by various 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): Starting June 2026, all government-backed projects must utilize India-made cells. Higher production costs (around ₹25/W for DCR modules versus ₹15/W for non-DCR) affect project economics.

• Production-Linked Incentive (PLI) Scheme: This encourages high-efficiency module production, favoring TOPCon and HJT, and aims to offset high capital expenditure costs for manufacturers transitioning to newer technologies.

• Basic Customs Duty (BCD): A 40% duty on imported solar modules and a 25% duty on cells promotes domestic manufacturing. While it favors Mono PERC (already produced domestically), it creates short-term cost barriers for TOPCon and HJT, which rely on imports.

• Approved List of Models and Manufacturers (ALMM): Only approved manufacturers can participate in government projects. This encourages quality control, but delays in listing newer technologies hinder their adoption.

3. Maintenance & Operational Challenges

Transitioning from Mono PERC to advanced technologies like TOPCon and HJT necessitates changes in operations and maintenance (O&M) strategies.

• Key Takeaways:
  • TOPCon requires additional PID monitoring and infrared inspections to detect soldering defects.
  • HJT demands specialized cleaning methods and regular electroluminescence scanning to prevent microcracks.

4. Cost Analysis & Future Outlook

While Mono PERC remains dominant, TOPCon is emerging as the next significant upgrade due to its lower transition costs. HJT, despite its high efficiency, requires government incentives and industry collaboration for large-scale adoption.

Conclusion: The Road Ahead for India’s Solar Industry

India’s solar PV transition is at a pivotal point. While Mono PERC continues to be widely used, the push for higher efficiency and long-term sustainability is generating interest in TOPCon and HJT. Government policies like DCR, ALMM, and PLI will be crucial in shaping future adoption. For industry leaders and investors, TOPCon presents the best near-term opportunity with moderate production line upgrades and higher efficiency benefits. However, long-term competitiveness will hinge on:

• Scaling HJT manufacturing.
• Reducing silver consumption.
• Optimizing production costs.

📌 India’s journey toward achieving over 100 GW of solar capacity will be defined by technological advancements, policy frameworks, and global competitiveness. By staying ahead of these developments, businesses and policymakers can position India as a leader in the next generation of solar innovation.