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We performed workfunction mapping of the cleaved interface of silicon heterojunction (SHJ) solar cell. While it has been widely accepted that the efficiency of solar cells depends on their electric contacts at various interfaces, no direct information on the electronic properties had been obtained on nm-scale. In this work, we employed Kelvin probe force microscopy (KFM) and simultaneously measured the workfunction and morphology of the cleaved interfaces on nm-scale for the first time. We show the measured workfunction differences between the surface layers on the cleaved SHJ solar cell, and discuss how such information can be used to improve the quality of the devices.

We investigated a new high efficiency low cost bifacial cell based on n-type substrate using a new simplified inline ion doping system, the so called ion shower. We were able to successfully form the boron doping layer and control the sheet resistance of the doped layer by controlling the doping and annealing parameters. Furthermore, we fabricated a bifacial Passivated Emitter and Rear Totally diffused (PERT) cell using the ion shower doping system to form a boron emitter. At first, PV performances were relatively low and the bifaciality was higher than 1. This result suggested that the recombination on the P+ side was greater than on the N+ side. Therefore, we applied the Alignment Free-Selective Emitter (AF-SE) technique to our cell to reduce the recombination loss of the emitter. As a result, all parameters were improved, and especially the increase in Jsc on the P+ side was remarkable, with the bifaciality decreased to 0.987. This clearly shows the effectiveness of AF-SE. In conclusion, we confirmed the feasibility of newly proposed high efficiency low cost n-type bifacial cell fabrication process using an ion shower doping system.