Trends in PV Cell Efficiency

Trends in PV Cell Efficiency

?In today’s brief, we will see the trend in efficiency in crystalline PV (c-Si).

Trends in Solar PV Cell Efficiencies:

We focus on c-Si because that is the most widely used PV technology. As per IEA[1], c-Si dominates about 97% of the global solar PV technology. And within that PERC (Passivated Emitter and Rear Cell) has 60% share and newer technologies such as TOPCon, hetero-junction and back-contact expanded to capture about 35% of the market share.

It is estimated, as PERC reaches its theoretical limit[2], newer technologies such as N-Type using TOPCon and HJTs[3].

Figure 1 below is the most famous chart in the solar industry. Compiled by NREL[4], this chart shows the trend in various PV cell technologies over the years. This chart focuses on the trend in the c-Si technology.

As we notice, since 1977, for c-Si, efficiency has improved from 13.9% to about 26.8% for research cell. Given the trend and data from NREL, the efficiency of the c-Si PV cell has improved by about 0.7% age points every year.

But it is interesting to note the annual improvement in efficiency between 1977 and 2003 was at the rate of only 0.3%. Whereas, between 2003 and 2022, the annual improvement was at the rate of 2.4% every year.

This is a hard-fought improvement in the most dominant PV-cell technology. And largely driven by the stupendous growth in solar PV power.

Other newer PV-cell technologies may have higher efficiencies such as the 3-junction (non-concentrator, 1-Sun) at 39.46%. But that is a Gallium-Indium-Phosphide technology. Not a Silicon technology. Depending on three elements (Ga, In are rare elements) instead of just one element (Si, very abundant) has its own supply constraints. So, the industry, in our opinion, is likely to continue to depend on Silicon for our renewable energy needs.

Cell efficiencies are better than module efficiencies. And we note that even module efficiencies have improved significantly in tandem with cell efficiencies.

For now, commercially available modules have an approximate efficiency of about 21.5%[1] and 22%[2]. And module sizes have gone up from 140Wp in early 2000’s to about 665W[3] achieving about 21.4% efficiencies.

On a separate note, Brendel 1996[4] estimates the 1-sun thermodynamic limit for Photovoltaics at 43%. So, the most efficient research cell, using GaInP, is quite close to that limit.

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[1] https://www.longi.com/us/products/modules/hi-mo-5/

[2] https://jinkosolar.us/eagle-modules/#eagle-g6

[3] https://static.trinasolar.com/sites/default/files/DT-M-0013_C%20Datasheet_Vertex_DEG21C.20_NA_EN_2023_PA1_web.pdf

[4] https://www.sciencedirect.com/science/article/abs/pii/0927024895001255

[1] https://www.iea.org/energy-system/renewables/solar-pv#tracking

[2] https://www.pv-magazine.com/2022/07/22/solar-panel-sizes-continue-to-get-larger-and-improve-lcoe-says-trend-report/

[3] https://www.cleanenergyreviews.info/blog/most-efficient-solar-panels#:~:text=Due%20to%20the%20many%20advances,from%20250W%20to%20over%20420W.

[4] https://www.nrel.gov/pv/assets/pdfs/cell-pv-eff-crysi.pdf