In the rapidly growing field of renewable energy, photovoltaic (PV) solar cells stand out as a vital technology. A critical component in the manufacturing of these solar cells is silver nitrate (AgNO₃). This compound is very important in creating a silver paste, which is applied to the solar cell's surface to form electrodes, a process that impacts the efficiency and longevity of the cells. During the process, the pH of silver nitrate is a key factor that must be meticulously controlled and measured to ensure optimal performance of the solar cells.

Why is the pH of silver nitrate crucial?

The pH of the silver nitrate solution influences the surface charge of the particles in the silver paste. These charges affect the dispersion and uniformity of the paste, which, in turn, determines the quality of the electrodes formed. A well-controlled pH ensures the paste spreads evenly and adheres properly to the solar cell's surface, leading to better conductivity and overall efficiency of the cell.

Electrode performance: The adhesion and thickness of the electrodes are directly impacted by the pH level. If the pH is too high or too low, it can compromise the bonding of the silver paste to the cell’s surface, leading to potential failures and reduced efficiency. Proper pH levels ensure the electrodes are uniformly thick.

Avoiding precipitation: Measuring the pH of AgNO₃ can be challenging due to its tendency to form a white precipitate of silver chloride (AgCl) when in contact with potassium chloride (KCl) electrolytes, which can clog routine pH sensors. Therefore, using specialized equipment that can handle these conditions is essential.

Best practices for accurate pH measurement

To tackle the challenges of measuring the pH of silver nitrate, METTLER TOLEDO offers the InLab Science Pro-ISM sensor, designed specifically for this purpose. Here are the best practices to ensure precise measurement:

Sensor selection: Opt for the InLab Science Pro-ISM sensor, which features a double reference electrolyte system with an outer hole for easy electrolyte exchange. This design allows the replacement of KCl with potassium nitrate (KNO₃), preventing the formation of AgCl precipitate.

Click here to select the right electrode for an application.

Electrolyte replacement: The innovative design of the InLab Science Pro-ISM sensor includes an outer bridge electrolyte that can be effortlessly switched from KCl to KNO₃ for obtaining accurate readings without any precipitation issues.

Calibration and maintenance: Ensure the sensor is calibrated properly before each use. The sensor should be allowed to stay in the wetting cap filled with KNO₃ for 30 minutes before calibration. Regular maintenance, such as cleaning with Thiourea solution, prolongs the sensor's lifespan and maintains accuracy.

Measurement practices: Always measure pH buffers and sample solutions at the same temperature. Perform triplicate measurements to ensure consistency and clean the sensor with deionized water after each use.

Cleaning and storage: If the sensor performance declines, a deep clean with thiourea and subsequent rinsing with KNO₃ and deionized water is recommended. Store the sensor in a wetting cap filled with fresh KNO₃ solution when not in use to maintain its functionality.

Verification and recalibration: After every 10 samples, perform a verification measurement. If results fall outside the required tolerance, recalibrate the sensor.

Source: Mettler Toledo

The precise control and measurement of the pH of silver nitrate are critical in the production of high-efficiency photovoltaic solar cells. The use of advanced sensors like the InLab Science Pro-ISM ensures accurate and reliable pH measurement. By following the best practices in sensor selection, calibration, maintenance and measurement, manufacturers can significantly enhance the performance and lifespan of their solar cells, contributing to the advancement of renewable energy technology.

Download the pH calibration poster to learn about the best practices. Users can also find the application note on pH measurement of silver nitrate here.

To contact the author of this article, email pHmatters@mt.com