Ultra-low reflective black silicon photovoltaics by high density inductively coupled plasmas

Abstract

Photovoltaics (PV) as a renewable source of energy has received renewed interest in the immediate provision of sustainable energy to meet market demand in recent years. A key challenge in clean energy research is to ensure that the technology not only provides a sustainable energy source during device operation, but is also environmentally sustainable during the manufacturing phase of the device lifecycle. Plasma sources have been conventionally employed in numerous surface nucleation and nanostructure growth processes due to highly controllable process parameters that enable precise control of material properties at the nanoscale. However, these processes usually employ toxic feedstock as a means to obtain favourable PV characteristics, such as nanotexturing. In this work, an inductively coupled plasma (ICP) system in a cascading cluster configuration setup was employed for fabrication of highly efficient nanotextured PV cells. A 2-step process was developed to use a high density N2 discharge for high density plasma immersion ion implantation (HD-PIII) in group V doping of c-Si samples for high quality junction formation. Subsequently, an Ar + H2 discharge was utilized for the simultaneous nanotexturing of the surface as well as passivation of surface defects through intense hydrogenation from the plasma generated radical flux. The resulting black silicon (b-Si) PV cells fabricated through this process typically have ultra-low reflectance of <1.8%, Voc of ∼540 mV, and Jsc of ∼24 mA × cm−2. In-situ plasma diagnostics were also performed to enable a truly deterministic method for obtaining optimal material properties based on plasma parameters instead of process parameters, which may vary for different reactor geometries.