An efficiency of 18.88% in selective emitter solar cells by metal pattern optimization

A high efficiency (η~18.88 %) mono-crystalline Si solar cell (Area=15.6 × 15.6 cm²) with a selective emitter structure used in the conventional diffusion process (POCl3) and the screen printed contact is presented in this paper. In particular, we focus on the improvement of fill factor (FF) by the front metal Ag portion and aspect ratio optimization. As a result, the front metal portion of 5.15% (printing thrice) represents the best in the FF of 77.68%. The fabricated solar cell with a selective emitter has the portion of high doping concentration (30 ohm/sq.) to just below the metal contact and the shallow emitter (80 ~ 90 ohm/sq.) of the rest of contacts. As a result, our selective emitter solar cell is accomplished by the Eff 18.88% when the front metal portion of 5.15% is applied during its printing thrice.