The global solar PV technology market is expected to grow beyond 150GW in 2021 according to many market studies. Compared to the cumulative installed solar PV capacity up to 2012, 100GW, today, the solar market is growing to become the new king of energy markets. This development was caused by the variety of technologies offered by Tier1 suppliers in the market writes Titus Koech, Technical Service Manager – SSA at JinkoSolar.
Technologies such as Passivated Emitter Rear Contact (PERC), Half Cut (Cut), Multi Busbar (MBB), Tiling Ribbon and bifacial cells have proven themselves to be mature and reliable. They have become mainstream technologies globally and in the MENA region.
PERC technology was a milestone in the solar PV market. PERC is today’s mainstream technology (p-type gallium doped) with a 90% share in the PV market. The technology shifted the market approach from low-efficiency low power modules into high-efficiency high power modules and paved the way for bifacial modules to become mainstream. It even led the market into poly to mono transition. But what is the next technology that will revolutionise the solar industry as PREC did?
Most are familiar with traditional p-type cell technology. With large-scale manufacturing of monocrystalline silicon wafers, p-type mono PERC cell technology has been deployed on a large majority of projects since 2017. Mainstream module manufacturers have used mono PERC due to a simple manufacturing process, low cost, and cell conversion efficiency improvements.
Solar PV technology: The trend chart of cell efficiency
However, the efficiency of PERC cells has approached a limit of 24.5%, and cost reduction has also slowed. Meanwhile, new cell technology is developing rapidly, and n-type cells are most likely to replace p-type cells to become the next-generation mainstream technology.
The traditional p-type cell uses a boron-doped silicon wafer substrate, which easily forms a boron-oxygen pair after initial illumination. It will lead to light-induced degradation after a recombination centre is formed by trapping electrons in the silicon wafer substrate.
In contrast, the n-type cell silicon wafer substrate is doped with Phosphorus, so there is almost no loss of recombination centre formed by the boron-oxygen pair, which greatly reduces light-induced degradation. For example, in TOPCon technology, the structure of the tunnel oxide layer further reduces the sub-surface recombination rate, which greatly optimises the cell conversion efficiency, and the upper limit can reach 28.2%~28.7%
The PV market is now dominated by the p-type modules where it makes up most of the production capacity of Tier1 suppliers along with limited capacities of n-type for specific markets and applications. However, since the industry is currently reaching the theoretical limits of PERC technology (around 24.5%), it’s clear that switching from p-type to n-type modules will be the next step in the market.
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N-type solar PV technology
N-type modules have been available in the market for quite a while, but they were always considered premium products. However, nowadays, the current developments of mature technologies such as Tunnel Oxide Passivated Contacts (TOPCon), solar cell technology n-type phosphorus-doped with a thin oxide between the emitter and Si wafer (base), and Heterojunction Technology (HIT), n-type phosphorus-doped with amorphous layers on c-Si wafers, along with the improvements in n-type production machines are allowing these technologies to become more competitive, with p-type modules. As a result, many Tier1 suppliers consider increasing the production capacity of n-type modules starting from 2022.</…….