[Paper Review] Axial vs. Radial Junction Nanowire Solar Cell

Vidur Raj, Hark Hoe Tan+1 more|arXiv (Cornell University)|Mar 24, 2021

Nanowire Synthesis and Applications118 references4 citations

TL;DR

This review provides a comprehensive comparative analysis of axial and radial junction nanowire solar cells, evaluating their optical absorption, device physics, and efficiency potential. It highlights how radial junctions offer superior light trapping and carrier collection, while axial junctions face challenges in radial transport, concluding with key challenges in nanowire solar cell development.

ABSTRACT

Both axial and radial junction nanowire solar cells have their challenges and advantages. However, so far, there is no review that explicitly provides a detailed comparative analysis of both axial and radial junction solar cells. This article reviews some of the recent results on axial and radial junction nanowire solar cells with an attempt to perform a comparative study between the optical and device behavior of these cells. In particular, we start by reviewing different results on how the absorption can be tuned in axial and radial junction solar cells. We also discuss results on some of the critical device concepts that are required to achieve high efficiency in axial and radial junction solar cells. We include a section on new device concepts that can be realized in nanowire structures. Finally, we conclude this review by discussing a few of the standing challenges of nanowire solar cells.

Motivation & Objective

• To systematically compare axial and radial junction nanowire solar cells in terms of optical absorption and device behavior.
• To identify critical device concepts enabling high efficiency in both axial and radial nanowire solar cell architectures.
• To explore novel device concepts enabled by nanowire structures for next-generation photovoltaics.
• To outline persistent challenges hindering the practical deployment and efficiency scaling of nanowire solar cells.

Proposed method

• Reviewing recent experimental and theoretical results on light absorption in axial and radial nanowire solar cells.
• Analyzing device physics, including carrier generation, transport, and collection mechanisms in both architectures.
• Evaluating the impact of nanowire geometry, doping profiles, and heterostructure design on photovoltaic performance.
• Comparing optical properties such as absorption efficiency and light trapping using nanowire arrays.
• Surveying emerging device concepts like core-shell, axial heterostructures, and radial doping gradients in nanowires.
• Synthesizing findings to identify performance bottlenecks and design limitations in current nanowire solar cell platforms.

Experimental results

Research questions

• RQ1 How do axial and radial junction nanowire solar cells differ in their optical absorption characteristics?
• RQ2 What are the key device physics mechanisms that influence carrier collection in axial versus radial nanowire solar cells?
• RQ3 What design principles enable higher efficiency in radial junction nanowire solar cells compared to axial ones?
• RQ4 What novel device concepts can be realized in nanowire structures to enhance photovoltaic performance?
• RQ5 What are the primary unresolved challenges limiting the efficiency and scalability of nanowire solar cells?

Key findings

• Radial junction nanowire solar cells exhibit superior light trapping and absorption due to the radial heterostructure, enabling efficient carrier collection.
• Axial junction nanowires face challenges in radial carrier transport, limiting their efficiency despite simpler fabrication.
• Radial junctions benefit from a larger junction area and better electric field distribution, enhancing photogenerated carrier collection.
• Optical absorption in nanowires can be tuned via diameter, length, and material composition, with radial designs showing higher absorption efficiency.
• Core-shell radial structures allow for better bandgap engineering and reduced recombination losses.
• Despite progress, challenges such as surface recombination, contact resistance, and scalable fabrication remain significant barriers to commercialization.