Lithography Patterning for Thin Film Solar Cells
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Solution Overview
Problem
Thin-film solar cells for indoor applications face reduced efficiency due to shunt leakage currents and patterning defects, particularly metal flakes, which are challenging to avoid in conventional laser scribing processes, especially under low light intensities.
Innovation Solution
A method involving lithography processes to form isolation and contact trenches in solar modules, reducing the probability of metal flakes and enhancing efficiency by allowing for smaller trench dimensions and flexible substrate use, thereby improving the series connection of solar cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser scribing is used to pattern material layers for series connection, then large area modules can be manufactured with automated processes, but metal flakes are generated causing shunt leakage currents that reduce cell efficiency
Solution Approach 1:
The patent extracts and removes the harmful metal flakes from the system by using lithography to create isolation trenches that completely separate metal contacts between adjacent cells, preventing flake-induced shunt leakage while maintaining automated manufacturing capability
Solution Approach 2:
The patent introduces an intermediary dielectric layer filled into isolation trenches created by lithography, which acts as a barrier to prevent metal flake contact between adjacent cell regions, thereby eliminating shunt leakage paths while preserving the benefits of laser-based material removal
2Ease of manufacture
If laser scribing is used for patterning, then series connection can be achieved, but dead areas are caused by the beam size constraint of approximately 50 to 60 μm, resulting in loss of active cell area
Solution Approach 1:
The patent replaces the mechanical laser beam patterning system with a lithography-based patterning system that uses photoresist and chemical etching, enabling trench widths below 50 μm and thereby increasing active cell area while maintaining ease of manufacture for series connection
Solution Approach 2:
The patent changes the critical parameter of trench width from 50-60 μm (laser limitation) to below 50 μm (lithography capability), thereby increasing the active cell area ratio while preserving the series connection functionality through modified patterning parameters
3Device complexity
If conventional patterning processes are used, then manufacturing can be simplified, but defects such as metal flakes are generated during processing of metal back side contact
Solution Approach 1:
The patent segments the patterning process into distinct lithography-based isolation trench formation and separate metal contact processing steps, preventing metal flake generation during patterning by avoiding laser processing of metal layers and thereby improving manufacturing precision
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 method significantly reduces shunt leakage currents and increases the active cell area, enhancing the overall efficiency of solar modules, especially in indoor environments with low light intensities, while maintaining cost-effectiveness.
Implementation Method 1
The first isolation trench and/or the contact trench and/or the second isolation trench are formed by applying a lithography process
Implementation Method 2
Thin-film solar cell technology based on appropriate semiconductive materials, such as amorphous silicon (a-Si:H), is very promising for generating low-cost solar energy
Data Source
AI summary
Solar thin film modules are provided with reduced lateral dimensions of isolation trenches and contact trenches, which provide for a series connection of the individual solar cells. To this end lithography and etch techniques are applied to pattern the individual material layers, thereby reducing parasitic shunt leakages compared to conventional laser scribing techniques. In particular, there may be series connected solar cells formed on a flexible substrate material that are highly efficient in indoor applications.