Tunnel Oxide Passivated Contact — TOPCon

This technology began replacing PERC (Passivated Emitter Rear Cell) as the mainstream global market standard from 2024.

PERC cells, which dominated the market throughout 2018-2023, increased efficiency by adding a passivation layer on the rear side of the cell, but were prone to energy loss from Auger recombination at high injection densities. TOPCon overcomes this limitation by adding a thin oxide layer of ~1.5 nm as a quantum tunnelling barrier, followed by a doped silicon layer (doped poly-Si) that moves charge carriers without direct contact between the metal electrode and the silicon substrate.

As a result, TOPCon cell efficiency reaches 25-26% under laboratory conditions, while commercial modules from mainstream vendors are at 22-24% [ITRPV 2024]. According to the 2024 edition of the ITRPV roadmap, TOPCon's market share is projected to surpass PERC globally in 2025-2026. Most large-scale panel manufacturers — including those supplying the Indonesian market — had already shifted their production lines to TOPCon by 2024-2025 [vendor datasheets, 2024-2026].

TOPCon is generally produced in a bifacial configuration because its cleaner rear structure supports receiving light from both sides. This efficiency advantage makes TOPCon relevant for factory roofs and commercial rooftops in Indonesia, where area is limited but the capacity target is high.

Indonesian PLTS Application Example

A textile factory in West Java with a 2,000 m² roof that previously could install only ~280 kWp using 370 Wp PERC modules can accommodate ~380 kWp with 450 Wp TOPCon modules in the same area — a ~36% capacity increase with no additional footprint. The annual production difference is estimated at 115-140 MWh based on West Java's average PSH of 4.7 kWh/m²/day [NASA POWER 1984-2023] and a performance ratio of 0.80.