Silicon Nanocrystals Embedded in Nanolayered Silicon Oxide for Crystalline Silicon Solar Cells
Ryohei Tsubata, Kazuhiro Gotoh, Masashi Matsumi, Markus Wilde, Tetsuya Inoue, Yasuyoshi Kurokawa, Katsuyuki Fukutani, Noritaka Usami
Abstract
This study describes the fabrication of silicon nanocrystals (Si NCs) in silicon oxide layers, which led to high-performance passivation and enhanced carrier transport in crystalline silicon (c-Si) solar cells. These Si NCs comprised nanocrystalline transport pathways in ultrathin dielectrics for reinforced passivating contact structures (NAnocrystalline Transport path in Ultrathin dielectrics for Reinforcing (NATURE) contacts). Si NCs were formed in silicon oxide layers by depositing hydrogenated amorphous silicon oxide (a-SiOx:H) with different oxygen concentrations, followed by postdeposition annealing (PDA). Based on microscopic images, the silicon oxide layer was maintained after PDA, and the Si NCs were formed in the silicon oxide matrix, leading to a relatively low recombination current (178.8 fA/cm2) compared with simple a-SiOx:H layer structures. Furthermore, the contact resistivity for the NATURE contact was 13.1 mΩ·cm2, which was comparable to that of a single a-SiOx:H layer with a low oxygen concentration. The developed NATURE contact structure expands the design flexibility scope for various functional devices containing a passivation contact layer. It allows for the production of c-Si solar cells with passivating contacts using thicker dielectric layers for improved reliability and long-term stability.