High-Resistivity Silicon Photovoltaic Cells for High Breakdown Voltage
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Solution Overview
Problem
Commercial silicon photovoltaic devices have breakdown voltages below 50-100 volts, leading to unreliable performance due to high failure rates of bypass diodes, and existing studies do not adequately address device reliability under real-world illumination and temperature conditions.
Innovation Solution
A high-efficiency silicon photovoltaic cell with very high breakdown voltages is achieved by combining a device architecture with low surface recombination and silicon wafers of high bulk resistivity (above 10 ohms centimeter), forming a heterojunction with n-type and p-type regions, which improves reliability and reduces design complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bypass diodes are used to prevent photovoltaic cells from going into breakdown, then device protection is provided, but failure rates increase and reliability decreases
Solution Approach 1:
The patent removes bypass diodes from the photovoltaic device by achieving inherently high breakdown voltages through the use of undoped substrates with bulk resistivity greater than 10 Ω-cm. This extraction of the bypass diode component eliminates the reliability issues and failure rates associated with these protective devices while maintaining device protection through the substrate's intrinsic properties.
Solution Approach 2:
The undoped substrate with high bulk resistivity provides self-protection against breakdown without requiring external protective components. The substrate's inherent electrical properties enable it to withstand high reverse biases and prevent breakdown, making the device self-protecting and eliminating the need for bypass diodes.
2Strength
If silicon wafers with high bulk resistivity (above 10 Ω-cm) are used, then breakdown voltage increases to close to 1000 V, but manufacturing complexity may increase
Solution Approach 1:
The patent changes the bulk resistivity parameter of the silicon substrate to greater than 10 Ω-cm, which fundamentally alters the electrical properties and enables breakdown voltages close to 1000 V. This parameter change is achieved through selecting undoped or lightly-doped float zone silicon wafers, which are commercially available and can be integrated into existing manufacturing processes.
Solution Approach 2:
The patent employs a composite structure combining undoped silicon substrate with high bulk resistivity and low surface recombination velocity materials. This composite approach leverages the advantageous properties of both the substrate and surface materials to achieve high breakdown voltage while maintaining manufacturability through established heterojunction technologies.
3Strength
If undoped substrates with bulk resistivity >>10 Ω-cm are used, then breakdown voltage increases, but device performance under real-world conditions remains unverified
Solution Approach 1:
The patent performs preliminary characterization of devices with undoped substrates under real-world operating conditions including temperature ranges and illumination intensities before deployment. This preliminary testing validates the device performance and reliability under actual operating conditions, ensuring that the high breakdown voltage property translates to reliable real-world performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides photovoltaic cells with breakdown voltages close to 1000 volts, enhancing the reliability and efficiency of photovoltaic devices while maintaining comparable thermal coefficients and performance across varying light intensities and temperatures.
Implementation Method 1
Photovoltaic devices with very high breakdown voltages are described herein
Implementation Method 2
silicon wafers with high bulk resistivity (above 10 ohms centimeter (Ω-cm))
Data Source
AI summary
Photovoltaic devices with very high breakdown voltages are described herein. Typical commercial silicon photovoltaic devices have breakdown voltages below 50-100 volts (V). Even though such devices have bypass diodes to prevent photovoltaic cells from going into breakdown, the bypass diodes have high failure rates, leading to unreliable devices. A high-efficiency silicon photovoltaic cell is provided with very high breakdown voltages. By combining a device architecture with very low surface recombination and silicon wafers with high bulk resistivity (above 10 ohms centimeter (Ω-cm)), embodiments described herein achieve breakdown voltages close to 1000 V. These photovoltaic cells with high breakdown voltages improve the reliability of photovoltaic devices, while reducing their design complexity and cost.