A novel method for the determination of the front contact resistance in large area screen printed silicon solar cells

The contact resistance at the interface of the semiconductor (Si)/metal (Ag) contact in a solar cell is generally small because it is made on a heavily doped silicon surface. In the case of large area terrestrial silicon solar cells contact is made by screen printing silver paste which has pores even after baking and sintering. Therefore the entire area is not active and the contact resistance is not entirely negligible. This paper describes the use of a simple method for the measurement of contact resistance of the front grid in a large area silicon solar cell based on the application of three-point probes using the existing fixed equidistant grid fingers of the solar cell. In addition, the value of the sheet resistivity is obtained from the measurement and is compared with that measured by the standard four-point probe method on different samples. The power losses due to current travelling through different resistive elements in the solar cell were obtained by using the standard formulae. The calculations show that power loss due to contact resistance is a small part of the total power loss. The total power loss agrees with that determined from the illuminated I-V characteristics of the solar cell.