Transparent Solar Cell Contacting Grid for Lower Ohmic Resistance
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Solution Overview
Problem
Existing methods for improving ohmic contact between a front contact grid and a doped layer in wafer solar cells result in high contact resistances, leading to reduced efficiency due to significant voltage losses and shading issues caused by contacting apparatuses, which affect the homogeneity of the process.
Innovation Solution
The use of transparent, full-surface conductive contacting apparatuses with optically transparent, electrically conductive materials or microscopically thin wires integrated into the surface, allowing for reduced shading and optimized contact points, enabling shorter current paths and more homogeneous process control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If opaque contacting apparatuses are used to make electrical contact with the front and back contacts, then electrical contact is achieved, but shading occurs that prevents complete illumination and reduces processing homogeneity
Solution Approach 1:
The contacting apparatus is made optically transparent or translucent instead of opaque, allowing light to pass through while maintaining electrical conductivity. This resolves the contradiction by enabling both electrical contact and complete illumination of the solar cell surface.
Solution Approach 2:
The contacting apparatus uses composite materials that combine electrical conductivity with optical transparency, such as transparent conductive oxides (TCO) like ITO or ZnO:Al, or fine metal wire networks embedded in transparent substrates. This allows simultaneous achievement of electrical contact and light transmission.
2Reliability
If conventional contacting apparatuses are used, then electrical contact is made, but voltage losses occur due to long current paths and significant resistance
Solution Approach 1:
The contacting apparatus is divided into multiple distributed contact points across the solar cell surface rather than single large contacts. This segmentation creates multiple parallel current paths, reducing overall resistance and voltage losses while maintaining reliable electrical contact.
Solution Approach 2:
The contacting apparatus transitions from point or line contacts to areal contacts that distribute contact points across the surface. This dimensional change creates shorter and more numerous current paths, reducing resistance and energy losses.
3Reliability
If the contacting apparatus covers the full surface for electrical contact, then contact reliability is improved, but shading increases and illumination is blocked
Solution Approach 1:
The contacting apparatus uses optically transparent or translucent materials that allow light to pass through while maintaining full-surface electrical contact. This resolves the contradiction by enabling both reliable contact and efficient illumination for processing.
Solution Approach 2:
The optical properties of the contacting apparatus are changed from opaque to transparent/translucent, fundamentally altering how light interacts with the contact structure while maintaining electrical functionality.
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 approach minimizes voltage losses and ensures more uniform processing across the solar cell, increasing efficiency by preventing shading and allowing for redundant contact designs, thus enhancing the ohmic contact quality.
Implementation Method 1
a point light source 4 configured and designed to illuminate the front 11 of the silicon wafer solar cell 1... a current flow is thus locally induced in the partial section
Implementation Method 2
a high current flows through a very small area and improves the metal-to-semiconductor contact there... A section of a partial region of the Sun-facing side is illuminated in the process, and a current flow is thus locally induced in the partial section. This current flow related to the section has a current density from 200 A/cm2 to 20,000 A/cm2
Data Source
AI summary
A device for improving ohmic contact between a front contact and a doped layer of a wafer solar cell having a front, a back, the front contact, the doped layer and a back contact. The front and back contacts are strip-shaped or grid-shaped. The device having: two contacting apparatuses for electrically contacting the front and back contacts; a voltage source having a pole for electrical connection to one contacting apparatus and a pole for connection to the other contacting apparatus; and two point light sources to illuminate the front and the back. The contacting apparatuses each have: an optically-transparent material coated with an optically-transparent, electrically-conductive layer; an optically-transparent material having microscopically-thin, electrically-conductive wires integrated into a surface of the optically-transparent material; an optically-transparent, electrically-conductive material having microscopically-thin, electrically-conductive wires integrated into a surface of the optically-transparent, electrically-conductive material; or, a braid or a network of microscopically-thin, electrically-conductive wires.