Recent extreme weather events have underscored the need to cut the CO₂ emissions that are driving up global temperatures. This requires a rapid transition of the energy economy to renewable energy sources, the cheapest being solar photovoltaics (PV). And our newly published research points to a way we can drive down costs of the shift even further using cheaper forms of silicon for highly efficient solar panels.
Australia has been leading the way with solar PV installations, but our solar energy journey is just beginning. This year, humanity hit a milestone of 1 terawatt (TW)—1 million × 1 million watts— of installed solar capacity. However, experts predict 70TW of solar PV may be needed by 2050 to power all sectors of the economy.
To help drive this rapid uptake of solar PV, we need solar panels that are high efficiency and low cost. Over the past ten years, some new solar cell designs have led to record high efficiencies. The problem is these designs also need higher-quality materials, which cost more.
Our recent research suggests we might be able to rethink the type of silicon needed to make these high-efficiency solar cells.
Not all silicon is equal
More than 95% of solar panels are made using silicon. The silicon used to make solar cells is similar to that used in computer chips. It’s effectively very pure sand.
To make a solar cell work, we need to form an electric field so the generated current can all flow in one direction. This is done by adding impurity atoms into silicon, a process known as “doping.”
In commercial panel manufacturing, the most commonly used type of silicon is “p-type” silicon. This material is doped with atoms that have one less electron than silicon, such as boron or more recently gallium.
We can then introduce a very thin layer on the surface full of atoms with one extra electron relative to silicon, which is called “n-type” silicon. Placing these two types of silicon together forms what is called a “p-n junction.” The massive difference in the number of electrons between the p-type region and n-type region forces electrons to move rapidly, creating an electric field that drives the current in our solar cell.
Conventional solar panels on Australian roofs today are overwhelmingly made using p-type silicon, as it is about 10% cheaper than the alternative “n-type” silicon, doped with phosphorus.
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