Back-Side Contact Photovoltaic Device Eliminates Front Shadowing
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Solution Overview
Problem
Current solar cells have low efficiency and high production costs, limiting their adoption as a mainstream energy source due to the inefficiency in converting solar energy into electric energy.
Innovation Solution
A photovoltaic device design featuring a window layer and an absorber layer with contacts on the back side to prevent shadowing, allowing for increased efficiency by allowing photons to reach the absorber layer without obstruction, and a method of fabricating these devices using epitaxial layers and specific semiconductor materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If contacts are placed on the front side of the solar cell to facilitate external connection, then electrical connection is simplified, but photons are blocked from reaching the absorber layer, reducing conversion efficiency
Solution Approach 1:
The patent inverts the conventional contact placement by moving all electrical contacts to the back side of the solar cell. This inversion eliminates front-side shadowing while maintaining electrical connectivity through the absorber layer, thereby resolving the contradiction between ease of connection and conversion efficiency.
Solution Approach 2:
The patent transitions from traditional planar contact placement to a three-dimensional configuration where contacts are positioned on the back surface and extend vertically through the absorber layer. This dimensional change allows electrical connection without obstructing the optical path on the front surface.
2Ease of manufacture
If conventional solar cell designs are used with front-side contacts, then manufacturing processes are well-established, but production costs remain high relative to efficiency levels
Solution Approach 1:
The patent changes the spatial parameter of contact placement from front-side to back-side configuration. This parameter change enables improved photon absorption and electron-hole pair generation, thereby increasing conversion efficiency and improving the efficiency-to-cost ratio.
3Reliability
If larger contact areas are used to reduce contact resistance, then electrical connection improves, but more photons are blocked from reaching the absorber layer
Solution Approach 1:
By inverting the contact placement to the back side, the patent eliminates the trade-off between contact area and photon absorption. Contacts can be made with sufficient area for reliable electrical connection without blocking front-side photons, as they are positioned on the opposite surface.
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 enhances the conversion efficiency of solar energy into electric energy by minimizing shadowing effects and reducing production costs through efficient contact placement and material selection, resulting in improved voltage and current output.
Implementation Method 1
the junction of a solar cell absorbs photons to produce electron-hole pairs, which are separated by the internal electric field of the junction to generate a voltage, thereby converting light energy to electric energy
Implementation Method 2
a window layer, an absorber layer disposed below the window layer such that electrons are generated when photons travel through the window layer and are absorbed by the absorber layer
Data Source
AI summary
Methods and apparatus for converting electromagnetic radiation, such as solar energy, into electric energy with increased efficiency when compared to conventional solar cells are provided. A photovoltaic (PV) device generally includes a window layer; an absorber layer disposed below the window layer such that electrons are generated when photons travel through the window layer and are absorbed by the absorber layer; and a plurality of contacts for external connection coupled to the absorber layer, such that all of the contacts for external connection are disposed below the absorber layer and do not block any of the photons from reaching the absorber layer through the window layer. Locating all the contacts on the back side of the PV device avoids solar shadows caused by front side contacts, typically found in conventional solar cells. Therefore, PV devices described herein with back side contacts may allow for increased efficiency when compared to conventional solar cells.