N-type or P-type cell : What is the world mulling for?
21st June 2018
A solar photovoltaic (PV) cell comes with variety of technology. This means that for a layman or a novice in the field, it becomes quite puzzling to select the right type of technology. For instance, the basic technology that could be found in today's market is p type & n type solar cell. While their purpose remains the same i.e. to capture sun's irradiance and turn it into energy, it's their manufacturing process which differentiates them. Anyone with knowledge on history of solar cell would know that the first solar cell was fabricated at Bell labs in 1954 which was of n-typemono-crystalline. Until 1980s, with the application of solar cells being mainly on satellites, the p-type solar cell had shown less degradation to exposure of cosmic rays. Thus for decades, the industry had kept continuous focus on p-type PV cell development. However with the changing market trends and the continued research on n-type solar cell in previous decade, its ability to outperform the currently in use p-type solar cell cannot be ignored. With the currently available diverse technology of solar cells and the predictions of advancement in efficiency of (almost) all these solar cell (both p-type and n-type) (Figure 1), it is important for us to understand what would be market inclined towards. Additionally, this blog would also give its readers an insight on technical advantages and disadvantages of both n-type and p-type solar cells.
Figure 1: Average stabilized efficiency values of Si solar cell (Source: ITRPV 2018)
From figure 1 above it is evident that both p & n-type solar cell shall experience a jump in their efficiency. However from an investor/ end user's perspective, it is important that you know the basics of these types of cells. As evident from figure 2 below, the p-type solar cell has p-type semiconductor at its base and vice versa (for n-type solar cell). This difference (in base) arises only when the doping on wafer (both multi and mono) is performed (Figure 3). Necessary to create a semiconductor junction which inducts the flow of current, the wafer is either doped with phosphorus (leading to n-type wafer) or boron (leading to p-type wafer).
Figure 2: Basic cell structure of p-type cell (on left) compared to n-type solar cell (on right)
Figure 3: Value chain of silicon wafer manufacturing
Let us now understand the advantages of both these technology. The first advantage of p-type cell is economics of the scale, due to the current and previous market trend which had demanded for p-type solar cell, they have an upper hand on economics of scale in manufacturing. This is because the entire value chain right from sand to solar cell is optimized as per p-type solar cell. Its next advantage is its cost competiveness compared to its opponent. In the current market scenario, initial cost may become a determining factor which gives p-type an upper hand. Coming to the advantages of n-type cell, firstly they are more efficient compared to their counterpart. This means that one can expect more power output and hence more revenue from the same area. Secondly they are susceptible to various degradations (explained later) experienced by a p-type solar cell. This means that we can have an increased lifetime of module made from such kind of cells. Additionally they are also less sensitive to impurities (compared to p-type cell). Thirdly levelized cost of electricity (LCOE) (a ratio of total cost incurred to total energy generated over plant's lifetime) can be moderately significant (sometimes even plant's return of investment (ROI)) when compared to p-type cell.
As we had mentioned in introduction of this blog, p-type cell are currently dominant in the market. With the introduction of highly efficient cell technology like PERC for commercial use, the solar market is expected to bolster. The PERC alike other cell technology comes in both p & n-type. However there are still lots of challenges which are needed to be addressed and the major being Light Induced Degradation (LID) and Light enhanced Temperature Induced Degradation (LeTID) for p-type cells. LID &LeTID are known to have cause significant reduction in power output in PERC module. A lot of efforts are necessary to increase the few practical remedies possible for (partially) eliminating LID &LeTID. N-type PERC cell however are known to be LID &LeTID free. This means that a steady power output can be expected out of such modules. As predicted by ITRPV, the market share of n-type mono solar cells shall rise to around 30% (Figure 4). We however believe that its market share would rise to around 40% by 2028 given its advantages.
Figure 4: World market share for different wafer types (Source: ITRPV)
We at Waaree Energies have understood such technology trend and have capability of producing both p-type and n-type cell based solar module. Our modules are backed up by the stringent quality certificates we have received from various national and international certifying agency. This means that the EPC player/ end customer shall be fully ensured that the modules they are using would be of premium quality.
Let us all pledge to make solar energy the primary source of energy in the near future.
RAHE ROSHAN HAMARA NATION