NiOx/MoOx bilayer as an efficient hole-selective contact in crystalline silicon solar cells

Abstract

Summary: Designing effective carrier-selective contact is a prerequisite for high-efficiency crystalline silicon (c-Si) solar cells. Compared to doped silicon thin films, wide-band-gap transition metal oxides (TMOs) feature low parasitic absorption, but their carrier selectivity and passivation being poor leads to a mediocre cell efficiency. Herein, we introduce a NiOx/MoOx bilayer as an efficient hole-selective contact in c-Si solar cells. A power conversion efficiency (PCE) of 21.31% is achieved using NiOx/MoOx bilayer, outperforming cells with a single layer of NiOx or MoOx. Upon depositing NiOx on MoOx, interfacial reactions modify the stoichiometry and defect chemistry in both oxides, leading to a band alignment beneficial for hole selectivity. By inserting a SiOx tunneling layer on c-Si surface to further suppress recombination, we achieve a PCE of 21.60% (fill factor 83.34%). Our work highlights a promising approach to improve the performance of dopant-free c-Si solar cells by employing cost-effective TMOs as hole-selective contact.

Keywords

• silicon heterojunction solar cells
• hole-selective contacts
• transition metal oxides
• hole extraction and electron blocking
• NiOx/MoOx bilayer
• SiOx tunneling passivation