InSECT : an inline selective emitter concept with high efficiencies at competitive process costs improved with inkjet masking technology

Abstract

The latest results in the application of selective doping structures to inline diffused industrial phosphorus emitters are presented. It was found that the efficiency of the cell can be increased substantially by partially etching back the highly doped layers created during the emitter diffusion. An average gain in the open circuit voltage (Voc) of 19 mV and a rise of the short circuit current density (Jsc) of 1.2 mA/cm², resulting from a significant decrease of recombination losses at the front surface of the cell, was measured. Combined with better fill factors achieved by contacting emitters with lower sheet resistivity, an efficiency gain of 1.4%abs was realized. The best cells show 18.1 % efficiency. The processes used for the investigations were performed on equipment used in large scale industrial production. Furthermore, novel inkjet masking methods were applied and their potential for improving selective emitters was evaluated. Inkjet printing is warp-free, applies no mechanical stress on the wafer and enables a precise structuring of the etch mask with very little lateral tolerances. This increase in precision lowers the areal fraction of low-resistance contact areas, resulting in lower emitter saturation current densities and thus improving the performance of selective emitters produced by inline processes.