CIGS Solar Cell Back Contact with Dielectric Passivation
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Solution Overview
Problem
Existing solar cells face challenges in reducing absorber thickness to lower material costs and processing time while maintaining efficiency, due to back contact reflectance issues and high charge carrier recombination at the surface.
Innovation Solution
A stacked-layered thin-film solar cell design featuring a substrate, conducting material, reflecting material, dielectric, semiconducting material, and transparent materials, with specific layer deposition and etching processes to minimize absorber thickness and reduce back surface recombination, including the use of Copper Iridium Gallium Selenide (CIGS) and anti-reflective coatings to enhance radiation absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If absorber thickness is reduced to lower material costs and processing time, then productivity and cost efficiency improve, but back surface recombination increases and efficiency decreases
Solution Approach 1:
A dielectric layer is introduced as an intermediary between the reflecting element and the semiconducting material. This dielectric layer passivates the interface, reducing charge carrier recombination at the back surface while allowing the absorber thickness to be reduced. The dielectric acts as a mediator that enables thin-film construction without sacrificing efficiency.
Solution Approach 2:
The solar cell employs a composite structure combining multiple materials: conducting material, reflecting material, dielectric material, and semiconducting material. This composite approach allows each layer to contribute specific properties - the reflecting material enhances infrared reflectance, the dielectric reduces recombination, and the thin semiconducting layer maintains absorption efficiency despite reduced thickness.
2Loss of time
If absorber thickness is reduced to decrease processing time, then manufacturing speed improves, but back contact reflectance for infrared wavelengths decreases
Solution Approach 1:
The dielectric layer serves as an intermediary that enables the use of thinner absorbers without compromising infrared reflectance. By passivating the back surface interface, it allows the reflecting element to maintain its effectiveness even when the absorber thickness is reduced, thus preserving infrared wavelength reflectance while enabling faster processing.
Solution Approach 2:
The invention changes the physical and chemical parameters of the back surface interface by introducing a dielectric layer with specific properties. This parameter change - the addition of the dielectric - allows the system to maintain high infrared reflectance with reduced absorber thickness, as the dielectric modifies the optical and electrical characteristics of the back contact interface.
3Quantity of substance
If absorber thickness is reduced to lower material costs, then quantity of material used decreases, but charge carrier recombination probability increases
Solution Approach 1:
The dielectric layer acts as a protective intermediary at the back surface interface, reducing charge carrier recombination through passivation. This allows the use of reduced material quantities in the absorber layer while compensating for the increased recombination probability that would normally accompany thinner films.
Solution Approach 2:
The dielectric layer is applied locally at the critical back surface interface where recombination occurs. This localized quality enhancement - passivation specifically at the back contact region - addresses the recombination issue without requiring increased absorber thickness throughout the entire device, thus maintaining material cost reductions while suppressing recombination at the problematic interface.
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 results in improved solar cell efficiency by reducing material usage, processing time, and increasing throughput, while minimizing reflectance and charge carrier recombination, thereby enhancing overall performance.
Implementation Method 1
The reflecting element is deposited on the conducting material... The art of solar cells addresses the conversion of radiation into electrical energy... back contact of a solar cell having reduced reflectance for infrared wavelengths
Implementation Method 2
The dielectric is deposited on the reflecting element... a surface with a high probability for charge carrier recombination leading to decreased efficiency
Implementation Method 3
The art of solar cells addresses the conversion of radiation into electrical energy... The semiconducting material is deposited on the dielectric...
Implementation Method 4
anti-reflective coatings to enhance radiation absorption... The first transparent material is deposited on the semiconducting material...
Data Source
AI summary
A stacked-layered thin film solar cell. The solar cell has reduced absorber thickness and an improved back contact for Copper Indium Gallium Selenide solar cells. The back contact provides improved reflectance particularly for infrared wavelengths while still maintaining ohmic contact to the semiconductor absorber. This reflectance is achieved by producing a back contact having a highly reflecting metal separated from an absorbing layer with a dielectric layer.