3D Conductive Electrode for Solar Cell Uniformity
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Solution Overview
Problem
The formation of a bottom electrode in photovoltaic devices is challenging due to the sensitivity of deep reactive ion etching (DRIE) processes, leading to series resistance issues and efficiency problems when the electrode is too thin, and current methods are costly.
Innovation Solution
A method involving the formation of pillar structures in a substrate, followed by a first electrode layer and a continuous photovoltaic stack, with a second electrode layer deposited to create gaps that are then wet etched to achieve a three-dimensional electrode of uniform thickness, reducing costs and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If DRIE is used to form the bottom electrode, then the electrode can be formed on textured structures, but the process is highly sensitive to thickness variations causing series resistance problems
Solution Approach 1:
Instead of using DRIE to etch through a deposited electrode layer (top-down approach), the patent deposits electrode material to conformally cover the textured substrate and then uses wet chemical etching to selectively remove material from recessed areas (bottom-up approach). This inversion of the conventional process sequence achieves uniform electrode thickness while avoiding the sensitivity issues of DRIE.
Solution Approach 2:
The patent changes the etching method from plasma-based DRIE to wet chemical etching, altering the etching parameters and mechanism. This parameter change enables better control over electrode thickness uniformity and reduces sensitivity to variations, thereby improving reliability by preventing series resistance problems.
2Manufacturing precision
If conventional lithographic patterning and DRIE processes are used, then precise electrode formation is achieved, but the manufacturing cost increases
Solution Approach 1:
The patent extracts and eliminates the expensive lithographic patterning step from the conventional process flow. By using conformal deposition followed by selective wet etching, the method achieves precise electrode formation without requiring complex lithography tools and processes, thereby reducing manufacturing cost while maintaining precision.
Solution Approach 2:
The patent replaces expensive, complex equipment (lithography tools and DRIE reactors) with simpler, more affordable wet chemical etching processes. This substitution uses cheaper materials and equipment that can be easily implemented, reducing the overall manufacturing cost while achieving the desired electrode 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
This approach results in a more uniform and contoured bottom electrode with improved absorption efficiency and reduced costs, eliminating the need for expensive lithographic patterning and DRIE processes.
Implementation Method 1
The second electrode layer is wet etched to open up the gaps or fissures and reduce the second electrode layer to form a three-dimensional electrode of substantially uniform thickness over the 3D photovoltaic stack.
Implementation Method 2
When a photon hits silicon, the photon may be transmitted through the silicon, reflected off the surface, or absorbed by the silicon if the photon energy is higher than the silicon band gap value. This generates an electron-hole pair and sometimes heat, depending on the band structure.
Data Source
AI summary
A photovoltaic device and method include forming a plurality of pillar structures in a substrate, forming a first electrode layer on the pillar structures and forming a continuous photovoltaic stack including an N-type layer, a P-type layer and an intrinsic layer on the first electrode. A second electrode layer is deposited over the photovoltaic stack such that gaps or fissures occur in the second electrode layer between the pillar structures. The second electrode layer is wet etched to open up the gaps or fissures and reduce the second electrode layer to form a three-dimensional electrode of substantially uniform thickness over the photovoltaic stack.