The contact resistivity test function is mainly used to test contact resistance, sheet resistance, contact resistivity, etc. These tests are crucial to ensure the reliability and performance of photovoltaic solar cells. Contact resistivity is an important parameter to measure the quality of contact between two conductors. It directly affects the current transmission efficiency and heat generation, thereby affecting the working performance of the entire circuit. Contact Resistance Tester, with its contact resistivity test and line resistance test functions, can accurately detect the resistance performance of solar cells and present it objectively.

Specific applications and advantages of TLM in contact resistivity measurements

Accuracy and applicability: Transmission line models can provide higher accuracy than traditional methods. For example, the quasi-two-dimensional transmission line model (QTD-TLM) is able to more accurately extract the specific contact resistivity (ρc) of ohmic contacts and is applicable to a variety of contact sizes and gap widths, whether alloyed or unalloyed contacts. In addition, the dot transmission line model is considered to be a better method for measuring metal-semiconductor contact resistivity.

Contact resistivity measurement formula

Analysis of the influence of temperature and material properties: The TLM method can be used to study the influence of different annealing temperatures on contact resistivity to optimize the material processing process. For example, in the specific contact resistivity measurement experiment of p-type GaN ohmic contact, by optimizing the annealing temperature, it was finally confirmed that the optimal ohmic contact can be obtained, and the specific contact resistivity is significantly reduced.

Reliability and stability: The TLM method can be used not only to measure contact resistivity but also to evaluate the reliability of the contact. For example, standard ohmic contacts on thin epitaxial layers of p-GaAs and n-InGaP were fully characterized and a method to extract the ohmic contact resistance was proposed. It utilizes a transmission line approach to an array of ohmic contacts and obtains the measurements required for their specific contact resistance as well as additional current and voltage measurements. The measured sheet resistances were R shMP 96 and 6.86 (Ohms Sq –1 ) respectively. In terms of its reliability, the reliability on n-InGaP is severely degraded after thermal annealing at 430°C for 30 minutes. Degradation increases first the metal pad resistance and then the contact resistance, while the resistance on p-GaAs remains unchanged. The Contact Resistance Tester produced by Millennial Solar has a testing range of 0.1~120mmΩ*cm＾2 during the detection of contact resistivity.

How to optimize contact resistivity measurements by adjusting TLM geometry

Contact resistivity measurements can be optimized by adjusting the TLM (transmission line matrix) geometry. For silicon solar cells, the measurement accuracy of contact resistivity is improved by improving the gridline TLM pattern. This includes explicit consideration of uncontacted (floating) grid lines, as well as employing commercial Ag paste through dielectric coating, screen printing and sintering to contact the different layers.

TLM test structure diagram

First, improving grid line design is one of the key steps to improve measurement accuracy. Traditional TLM patterns may have untouched grid lines, which may cause deviations in measurement results. By optimizing grid line layout and design, the number of such untouched grid lines can be reduced, thereby improving measurement accuracy and repeatability.

Second, screen printing and sintering through dielectric coatings using commercial Ag paste is an effective way to ensure effective contact with the different layers. Dielectric coatings can help improve contact stability and durability, thereby reducing changes in contact resistivity due to changes in the medium. In addition, the use of commercial Ag paste can provide good electrical conductivity and ensure effective transmission of current in the contact area, further improving the accuracy of the measurement.

According to the latest literature, a new device uses the TLM (Transmission Line Model) method to shorten the specific contact resistance measurement operation time. Each measurement point takes approximately 1 minute and a full-scale solar cell mapping is obtained in an acceptable time.

Contact Resistance Tester has contact resistivity testing function, which can achieve fast, flexible and accurate testing. The line resistance test function is mainly used for the line resistance of grid lines and cut cell with a length of 230mm.

Contact Resistance Tester

E-mail: market@millennialsolar.com

● Static test repeatability ≤1%, dynamic test repeatability ≤3%

● Line resistance measurement accuracy can reach 5% or 0.1Ω/cm

● Contact resistivity test and line resistance test can be switched at will

● A variety of probe heads can be customized for measurement and analysis

Contact resistivity testing is critical to the performance and reliability of photovoltaic solar cells. Contact Resistance Tester has high-precision contact resistivity and line resistance testing functions, with a wide testing range and high repeatability. The use of advanced (TLM) detection technology significantly improves measurement accuracy and reliability. In the future, Millennial Solar will also work with many photovoltaic enterprise users to innovate products and empower new capabilities!