Industrially feasible mc-Si solar cells with fine line printed front contacts on high emitter sheet resistance towards 17% efficiency

To achieve higher efficiencies without extra-cost is the major goal of research and development in crystalline silicon solar cell production technology. This goal can be addressed by fine line printing. Therefore, the focus of this work will be the combination of fine line printed front contacts and high emitter sheet resistances. A detailed study of fine line front contacts is presented. Therefore, an electrical analysis based on solar cell results as well as an optical analysis based on microscope pictures are carried out. Furthermore, the contact characteristic of different silver pastes as a function of the emitter sheet resistance is analyzed. As additional approach fine line printed front contacts as seed layer for a two-step metallization are discussed within this work. Both concepts, the one- and two-step metallization, will be compared with each other. Moreover, the use of MWT (metal wrap through) solar cells [1] allows a further efficiency increase [2]. Hence, MWT solar cells with fine line screen printed front contacts are developed and characterized in this paper. Efficiencies up to 16.8% are realized with mc-Si MWT solar cells.