Understanding the Basics of Photovoltaic Cell Metrology

In recent years, the need for sustainable energy sources has increased dramatically, thus leading to substantial developments in renewable energy technologies such as photovoltaic (PV) cells. A photovoltaic cell, also called a solar cell, is a single device that converts sunlight into electrical energy through semiconducting components. Larger PV units, called modules or panels, are formed by connecting many individual cells and can be configured in different ways depending on their application and industry setting. 

Because of the significance of PV cells for renewable energy, it is crucial to understand their internal structures and properties so these can be utilized correctly and enhanced where necessary. This is where photovoltaic cell metrology comes into play, which is the science of characterizing the electrical and optical properties of PV cells1 to understand performance and improve cost and efficiency. In this blog post, we will provide an overview of photovoltaic cell metrology, focusing on the importance of thin film thickness.

Fundamentals of Photovoltaic Cell Metrology

Photovoltaic cell metrology is necessary to further develop and optimize PV cells as it helps scientists understand their properties and how this impacts their applications, such as generating electricity from solar energy. The efficiency of PV cells is measured by how much electricity is released from the cell compared to the energy generated by the amount of light it receives2. Other vital measurements include current-voltage characteristics, external quantum efficiency (EQE), reflectance, and thickness and uniformity of the PV cell. In addition to the above mentioned aspects, the materials used in manufacturing the PV cells and the cell design impact cell performance and are also considered vital measurements.

The primary goal of photovoltaic cell metrology is to improve the measuring methods used to accurately characterize the electrical and optical performance of PV cells. PV cell metrology is also important for helping scientists develop a standard cell that can be calibrated to and used as a reference.

Film Thickness and Photovoltaic Cell Performance

One of the most important factors in PV cell performance is the films, critical to solar radiation absorption and converting sunlight to electricity. Typically, the thicker the film, the more light it will absorb. In turn, this leads to the higher efficiency of PV cells and their processes. However, this is not always the case because if a film is too thick, it can cause light reflectance instead of absorption, and if a film is too thin, it may not absorb enough light. 

There are different types of PV cells, including the traditional crystalline silicon solar cell and thin film solar cells, and each will have optimal properties. Film thickness is essential, and the ideal range depends on other components used to manufacture the cells. If the thickness cannot be changed, other properties of the cell can be modified to increase the cell’s efficiency. Therefore, optimizing the film thickness of photovoltaic cells is crucial for achieving high efficiency and performance. 

CRAIC Technologies and Photovoltaic Cell Metrology

Measuring film thickness in PV cells is crucial for further development and optimizing their efficiency. This can be conducted via several methods, such as ellipsometry, scanning electron microscopy (SEM), and X-ray diffraction. Each method has advantages and disadvantages, making it vital to use the most suitable method for your applications.  

At CRAIC Technologies, our 2030XL PRO™ microspectrophotometer is ideal for measuring film thickness for thin film photovoltaics, optical coatings, and semiconductor devices. It is a non-destructive, effective method that keeps samples safe from damage, allowing them to be reused, and for measurements to be taken promptly. In addition to the 2030XL instrument, CRAIC has also developed the CRAIC FILMPRO™ software that enables the measurement of film thickness values through reflectance or transmittance, so whatever materials used in the PV cells can be measured accurately. 

To learn more about measuring film thickness of photovoltaic cells, contact a member of CRAIC Technologies today.

References

  1. https://www.nrel.gov/docs/fy99osti/29591.pdf
  2. https://www.energy.gov/eere/solar/solar-photovoltaic-cell-basics
  3. https://www.nist.gov/programs-projects/electrical-performance-measurements-solar-photovoltaic-cells-and-arrays