Application of Silicon Carbide in Photovoltaic Industry

With the increasing global energy demand, fossil energy, mainly oil, coal and natural gas, will eventually be exhausted. In addition, fossil energy will also cause serious environmental pollution during use. In order to solve the above problems, renewable energy such as solar energy, wind energy, hydropower and nuclear energy have attracted people’s attention.

The main way to utilize solar energy is photovoltaic power generation. Compared with other power generation technologies, photovoltaic power generation has the advantages of being green and environmentally friendly, having sufficient solar energy resources, being safe and reliable in the power generation process, and being easy to install and transport power generation equipment. It is foreseeable that the large-scale promotion of photovoltaic power generation will have a positive impact on the governance of energy and environmental crises.

According to the principle of photovoltaic power generation, when sunlight shines on photovoltaic components (such as solar panels), photons interact with electrons in photovoltaic materials, causing electrons to escape from the materials and form photocurrent, which is direct current. Since most electrical equipment is powered by AC, the direct current generated by the photovoltaic array cannot be used directly, and it is necessary to convert the direct current into alternating current to achieve photovoltaic grid-connected power generation.

The key device to achieve the above purpose is the inverter, so the photovoltaic grid-connected inverter is the core of photovoltaic power generation technology, and the working efficiency of the inverter largely determines the utilization efficiency of solar energy.

Power devices are the core components of photovoltaic grid-connected inverters. Nowadays, various semiconductor devices used in the electrical industry are mostly based on silicon (Si) materials and have developed quite maturely. Si is a semiconductor material that is widely used in various electronic tubes and integrated circuits. As the use of power semiconductor devices becomes increasingly diverse, the use of silicon devices is restricted in some applications with high performance requirements and harsh working environments. This requires people to develop semiconductor devices with better performance. As a result, wide bandgap semiconductor devices such as silicon carbide (SiC) came into being.

Compared with silicon-based devices, silicon carbide devices exhibit a series of remarkable excellent properties:

(1) High breakdown electric field strength: The breakdown electric field strength of SiC is about 10 times that of Si, which makes SiC devices have higher blocking voltage and can work under higher electric field conditions, which helps to improve power density.

(2) Wide bandgap: SiC has a lower intrinsic carrier concentration at room temperature, which will lead to lower on-resistance in the on state.

(3) High saturation drift velocity: SiC has a higher electron saturation drift velocity, which helps it reach a steady state faster during the switching process and reduces energy loss during the switching process.

(4) High thermal conductivity: SiC has a higher thermal conductivity, which will significantly improve the power density, further simplify the design of the heat dissipation system, and effectively extend the device life.

In short, silicon carbide power devices provide the required low reverse recovery and fast switching characteristics to achieve “high conversion efficiency” and “low energy consumption” of photovoltaic inverters, which is crucial to improving the power density of photovoltaic inverters and further reducing the cost per kilowatt-hour.