As the final project of the Electronic and Photonic Devices course (ES 173), I and four other group members formulated a proposal for solar-cell research. Our team chose to work with black Silicon (b-Si) – a term used for etched crystalline Silicon (c-Si) to produce a surface dense with pillar-like structures with widths up to 2 um.
B-Si is a promising material as it increases single-junction solar cell efficiency solely through optimizing Silicon surface geometry. Without rare materials and with a multitude of methods available to process c-Si into b-Si, we believe that b-Si solar cells can be manufactured at competitive costs and greater efficiencies than current c-Si cells. Utilizing my cleanroom and nanofabrication experience, I’ve written the process flow and introduced my peers to the fundamentals of different thin film and etching processes.
I am currently taking a course on nanofabrication, where I aim to produce high-efficiency b-Si solar cells based on this proposal. Details about the proposal can be found below.
We chose dry reactive ion etching (DRIE) process for b-Si formation and varied the number of cycles of DRIE to vary b-Si ‘pillar’ height. Previous research has shown greater absorbance with greater pillar heights. We chose atomic layer deposition (ALD) for the passivation layer and varied number of ALD cycles to control passivation layer thickness. Previous research has shown greater current density for greater passivation layer thicknesses. However, it is also known that increasing passivation layer thickness reduces absorbance, and increasing pillar heights reduces current density.
Previous research has not established a consistent pillar height, b-Si formation method, thus it is unclear if the hypothesized simple inverse relationships will hold for different configurations. For this reason, we’ve proposed a two-parameter sweep to optimize b-Si solar cell manufacturing.
This project is a work in progress. It will be updated as developments occur.
Last update: Jan 2022.