Light-Induced Plating of Metal Contacts on Silicon Photovoltaic Cells

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Solution Overview

Problem

Existing methods for plating metal contacts on photovoltaic cells, such as electroplating, can result in breakage of fragile silicon substrates due to the need for electrical connections, and electroless plating suffers from instability and slow deposition rates.

Innovation Solution

A light-induced plating method using a composition containing soluble silver ions and an agent to solubilize aluminum ions on the back surface of the solar cell, allowing metal deposition without electrical contact, utilizing a neutral pH to prevent corrosion and ensure controlled dissolution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electroplating is used to deposit metal contacts on photovoltaic cells, then high conductivity and good electrical contact are achieved, but the fragile silicon substrates may break due to the need for electrical connections

Engineering Contradiction:

Improvesubstrate integrityVSAvoidelectrical connection requirement

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the requirement for external electrical connections by utilizing the photovoltaic cell's own generated electricity to drive the plating process. The cell is illuminated to generate current, which is then used to electroplate metal contacts directly onto the cell surface without needing external connection devices, thereby eliminating the source of mechanical stress that causes substrate breakage

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The photovoltaic cell serves itself by using the electrical current it generates through light absorption to drive the electroplating process. The cell's own output power is utilized to deposit metal contacts, eliminating the need for external power sources and complex connection apparatus, thus reducing device complexity while maintaining substrate integrity

Inventive Principle:

Principle #25Self-service

2Productivity

If electroless plating is used to deposit metal contacts, then no electrical connections are needed, but the deposition rate is slow and the process is unstable

Engineering Contradiction:

Improvedeposition rateVSAvoidprocess stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the operational parameters by using controlled electroplating with adjustable current density and illumination intensity. This allows optimization of the deposition rate while maintaining process stability through electrical control, overcoming the inherent slowness and instability of electroless plating methods

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The electroplating process is controlled by feedback from the photovoltaic cell's own electrical output. The current generated by the cell under illumination directly controls the plating rate, providing automatic feedback control that ensures stable and repeatable deposition without the instability problems of electroless plating

Inventive Principle:

Principle #23Feedback

3Reliability

If the metal pattern on the front-side intercepts incident radiation, then low resistance path for current collection is achieved, but the amount of radiation absorbed for current generation is reduced

Engineering Contradiction:

Improvecurrent collection efficiencyVSAvoidradiation interception loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent applies metal contacts only in specific localized patterns on the photovoltaic cell surface rather than uniform coverage. This selective placement creates low resistance current collection paths at critical locations while leaving most of the cell surface available for light absorption, thus resolving the contradiction between current collection efficiency and radiation interception loss

Inventive Principle:

Principle #3Local quality

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

This method achieves faster plating rates without substrate breakage and improves deposition stability, resulting in thicker, more uniform metal layers on the front side and reduced corrosion on the back side, enhancing the efficiency and reliability of metal contact formation on photovoltaic cells.

Implementation Method 1

Solar cells are photovoltaic cells or modules, which convert sunlight directly into electricity. When light (ultraviolet, visible and infrared radiation) strikes the cell, a certain portion of it is absorbed within the semiconductor material, such that the energy of the absorbed light is transferred to the semiconductor and an electrical current is produced.

Methodology Applied

Scientific EffectPhotovoltaic effect: Photovoltaic Effect

Implementation Method 2

Methodology Applied

Scientific EffectElectroplating: Electroplating

Data Source

PatentUS8956687B2Light induced plating of metals on silicon photovoltaic cells

Publication Date: 2015.02.17 MACDERMID ACUMEN INC

AI summary

A method and composition for plating metal contacts on photovoltaic solar cells is described. The cell is immersed in an aqueous bath containing platable metal ions and a solubilizing agent for aluminum or aluminum alloy ions from the back side of the solar cell. The cell is then exposed to light, causing the two sides of the cell to become oppositely charged. The metal ions are plated without requiring an external electrical contact.