[26p-F408-1~11] 16.3 Bulk, thin-film and other silicon-based solar cells

[26p-F408-1] Heterojunction Ge Solar Cells with an Efficiency of 8.6%

〇Makoto Konagai¹, Kimihiko Saito², Kazuyoshi Nakata¹, Yukimi Ichikawa¹, Naoki Suyama¹, Ryousuke Ishikawa¹ (1.Tokyo City Univ., 2.Fukushima Univ.)

Keywords:Silicon solar cell, Heterojunction, Germanium solar cell

In order to improve the efficiency of the heterojunction Ge solar cell, in addition to the substrate cleaning process, the carrier concentration of the wafer, the thickness of the wafer, and the optimization of the passivation structure using a-Si:H should be solved. In this presentation, we will focus on the relationship between the carrier concentration of the wafer and the cell characteristics. Unlike the heterojunction Si solar cell, the carrier concentration of the wafer has a great influence on the solar cell characteristics in the Ge system. Here, Ge solar cells were prepared using three types of Ge wafers from 1 × 10¹⁶ /cm³ to 3 × 10^{1 8}/cm³. As a result, a conversion efficiency of 8.6 % was obtained on a wafer with a carrier concentration of 2.5 × 10¹⁷ /cm³. This value is the highest among the heterojunction Ge solar cells reported so far. The open circuit voltage is as high as 291 mV. In addition, the Electroluminescence (EL)-EQE of 7 × 10^-4 % was obtained. This value is an order of magnitude higher than that of cells with Voc ~ 200 mV.