A Novel TLM Analysis for Solar Cells

Abstract

Despite its widespread usage, the linear regression method used to obtain contact resistivity and sheet resistance from the transmission line model (TLM) can lead to huge errors. The method assumes that contact parameters (both electric and geometric) are identical across the probed structure, such as a solar cell. In contrast, the contact parameters display various processassociated inhomogeneities. This paper analyzes the limitations of the linear fit method by using mathematical analysis and measurements on the front-side Ni-Cu plated contacts of a passivated emitter and rear contact (PERC) solar cell. It presents a new evaluation method based on the compartmentalization of contact resistance and emitter sheet resistance of a TLM network. The relative increase in the uncertainty of the extracted contact parameters with decreasing contact resistance is verified and linked to strong error coupling. A large error (20%-180%) is observed in the extracted values of the contact resistance for an assumed (5%-40%) scatter in the sheet resistance values, when a linear fit is used on simulated data with absolutely no pre-estimated error in the contact resistance. The presented method enables the detection and elimination of the influence of bad contacts along with minimal error propagation, which is imperative for contacts with small opening width and lower values of contact resistivity.

Curing conditions for low‐resistivity contacts on transparent conductive oxide layers for different solar cell applications

“…In addition, screen‐printed and dispensed electrodes result in a comparable level of contact resistivity 19,20 . When interpreting the results of contact resistivities, the measurement inaccuracy of the TLM should be kept in mind 51 . Furthermore, it must be pointed out that the manufacturing process and the composition of the ITO layers have a distinct effect on the contact formation of the electrodes to that layer and consequently on the contact resistivity values, as described in the literature 52,53 …”

“…19,20 When interpreting the results of contact resistivities, the measurement inaccuracy of the TLM should be kept in mind. 51 Furthermore, it must be pointed out that the manufacturing process and the composition of the ITO layers have a distinct effect on the contact formation of the electrodes to that layer and consequently on the contact resistivity values, as described in the literature. 52,53 The data allow the following observation: The lateral electrode resistance R lateral predicts if a contact between the Ag electrode and the ITO layer is formed or not.…”

Comparison of the Values of Solar Cell Contact Resistivity Measured with the Transmission Line Method (TLM) and the Potential Difference (PD)

“…The resistivity is understood to be the quantity that characterises the metal–semiconductor junction, considering the area above and below the junction. The value of contact resistance, which depends on the type of paste used, the substrate resistance, and the temperature of the metallisation process, can be determined experimentally—for example, by using the TLM (transmission line model) method [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ] or the PD (potential differences) method [ 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. In the case of the TLM method, the measurement consists of forcing an electric current signal between the selected pair of adjacent front conductive lines on the tested sample through the supply soda and the spontaneous generation of a potential difference in them through the measuring probes ( Figure 1 a).…”

Dopant‐free passivating contacts for crystalline silicon solar cells: Progress and prospects

“…However, standard CSM and TLM cannot deliver an accurate extraction of ρ c when it comes to contacts that show Schottky behavior such as HTL/ n ‐Si 74,82 . In addition, by algebraic analysis and experimental verification, Mir et al revealed that certain assumptions of linear regression may cause the ρ c to be seriously overestimated, resulting in inhomogeneities both at wafer level and contact level 83 . Meanwhile, Wang et al proposed an expanded CSM which has generally higher precision confirmed by simulation 74 …”