Electrical and Computer Engineering ETDs

Publication Date

Spring 5-11-2024

Abstract

Renewable energy sources, such as solar power, are rapidly expanding worldwide to meet increased energy demands. However, these sources are exposed to challenging environmental stressors, such as extreme wind, heavy snow loads, and hailstorms that can cause irreversible damage to the crystalline semiconductor solar cells. Today, single crystalline silicon solar cells dominate the market, and our work is focused on improving their reliability against environmental stressors. One of the main degradation mechanisms caused by environmental stressors is cell cracks. These microcracks can go virtually undetected and lead to reduced power output from solar modules over time. To solve this engineering problem, we have investigated the use of low-cost carbon nanotubes as an ingredient in silver metal matrix composite paste (MMC). In place of conventional commercial silver paste, the composite paste is used as mechanical reinforcement of the front side metallization of Passivated Emitter and Rear Contact (PERC) cells. The resulting metal contacts, also known as gridlines or fingers on silicon solar cells, show enhanced fracture toughness (> 7x), improved ductility where the critical strain increases by > 7x, and electrical gap-bridging of cell cracks (> 50 um gaps). In addition, the composite gridlines lead to improved cell efficiency by promoting silver particle sintering and lowering the contact resistance between gridlines and underlying silicon. Recent mini-module testing demonstrates that we can increase the module lifetime by > 1.5x against cyclic mechanical stress caused by environmental stressors. Our solution simultaneously improves module durability and efficiency. This dissertation work ranges from materials engineering, modeling

Keywords

Photovoltaics, Composite metallization, Cell cracks, Crack tolerance, Durability

Sponsors

U.S. Department of Energy under the DuraMAT program Award Number RGJ-8-82224, DOE SETO Award Number DE-EE0009013, DOE CINT Award Number 2019AU0023, NSF Award Number 1635334, and NMSBA.

Document Type

Dissertation

Language

English

Degree Name

Electrical Engineering

Level of Degree

Doctoral

Department Name

Electrical and Computer Engineering

First Committee Member (Chair)

Sang M. Han

Second Committee Member

Jane Lehr

Third Committee Member

Tito Busani

Third Advisor

Yu-Lin Shen

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