Minimizing the electrical losses on the front side: Development of a selective emitter process from a single diffusion

Abstract

In this paper we present latest results in the development of a process for the fabrication of a selective emitter structure on mono- and multicrystalline silicon solar cells. The process is based on an approach that was first introduced by Zerga et al. [1]. We have chosen a wet chemical route for an emitter etch back where the areas of the wafer that are intended for emitter metallization are shielded from etching by a screen printable etch barrier. The etch barrier is later removed by wet chemical etching. The process has yielded a gain in open circuit voltage of more than 1% and a gain in short circuit current of more than 2%. The overall efficiency gain was more than 0.3%abs due to slightly lower fill factor of the cells

Non-Vacuum Process for Production of Crystalline Silicon Solar Cells

“…A selective emitter structure is an optimum tradeoff to combine these both emitter conditions with highly doped low sheet resistance regions under the printed contact fingers and lowly doped high sheet resistance regions between the fingers [41]. By the advantage of that, selective structures lower the surface recombination velocity of minority carriers [42], and leads to reduced contact series resistances as well [43,44]. Additionally, blue response of solar cells can be improved [45,46], high open circuit voltage and fill factor [47] can be achieved owing to the selective emitter structures.…”

Recent Developments on Silicon Based Solar Cell Technologies and their Industrial Applications

“…The etch-back process in combination with a masking step is an industrially feasible scheme to form a selective emitter structure on p-type wafers. By changing the initial POCl 3 diffusion to 20 ohm/square and etching back to 95 ohm/square, a maximum efficiency of a selective emitter solar cell was measured to 19.0% [33].…”

Manufacturing 100-µm-thick silicon solar cells with efficiencies greater than 20% in a pilot production line

“…Both selective, heavily doped layers were created by means of wet-chemical etch-back solutions. The selective phosphorous BSF is created via an etch-back process which has been presented in [29], whereas the boron emitter etch-back has been introduced in [30]. These selective doping structures avoid the trade-off between high surface doping concentration to achieve low contact resistance and high emitter sheet resistance to minimize J 0e .…”