Ag-Doped CdTe Photovoltaic Absorber Layer Fill Factor
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Solution Overview
Problem
Thin film photovoltaic devices face a challenge in maintaining high conversion efficiency as the sulfur or selenium content in CdTe absorber layers increases, leading to a rapid drop in Fill Factor (FF) at higher (ISC*VOC) product values, which reduces overall energy conversion efficiency.
Innovation Solution
Doping the CdTe absorber layer with specific proportions of copper (Cu) and silver (Ag) as co-dopants, along with a graded selenium profile, to enhance voltage (VOC) and current (ISC) without compromising the Fill Factor, thereby improving the potential total power (PT) and conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sulfur or selenium content in CdTe absorber layer is increased, then infra-red absorption and ISC are improved, but Fill Factor drops rapidly at higher (ISC*VOC) product values
Solution Approach 1:
The patent applies parameter changes by systematically varying the sulfur and selenium content ratios in the absorber layer, along with adjusting dopant concentrations (Cu, Ag, Au) to optimize both infra-red absorption and Fill Factor simultaneously. This involves changing compositional parameters to achieve a balance where high (ISC*VOC) product values are maintained without causing rapid FF degradation.
Solution Approach 2:
The patent uses composite materials by creating a multi-element absorber layer combining CdTe with controlled amounts of sulfur and selenium, along with multiple dopants (Cu, Ag, Au). This composite approach allows the material to simultaneously achieve improved infra-red absorption from S/Se while maintaining electrical properties through dopant combinations that preserve Fill Factor at high power output levels.
2Length of moving object
If grain size and thickness of CdTe absorber layer are increased, then VOC is improved, but Fill Factor drops at higher (ISC*VOC) product values
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness of the absorber layer and the size distribution of grains within it, while simultaneously adjusting dopant concentrations. This coordinated parameter optimization ensures that increased thickness and grain size improve VOC without causing the Fill Factor to drop at high (ISC*VOC) values.
Solution Approach 2:
The patent applies local quality by creating variations in grain size distribution and dopant concentration throughout the absorber layer thickness. This allows different regions of the layer to have optimized properties - for example, larger grains in certain regions for high VOC while maintaining appropriate dopant levels to preserve Fill Factor performance at high power output.
3Power
If (ISC*VOC) product is increased, then total potential power is improved, but Fill Factor drops rapidly, reducing conversion efficiency
Solution Approach 1:
The patent applies parameter changes by systematically adjusting multiple parameters including S/Se content, dopant concentrations (Cu, Ag, Au), absorber layer thickness, and grain size distribution. These coordinated parameter changes enable the device to achieve high (ISC*VOC) product values while maintaining Fill Factor, thereby maximizing conversion efficiency rather than allowing it to drop.
Solution Approach 2:
The patent uses composite materials with multiple elements (Cd, Te, S, Se) and multiple dopants (Cu, Ag, Au) in specific combinations. This composite approach creates an absorber layer that can simultaneously achieve high total potential power and maintain high Fill Factor, resolving the contradiction between power output and efficiency.
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 use of Cu and Ag co-doping in conjunction with a selenium gradient in the absorber layer increases the potential total power (PT) and maintains a higher Fill Factor (FF) at higher (ISC*VOC) product values, resulting in improved conversion efficiency and stability of the photovoltaic devices.
Implementation Method 1
the energy from the solar radiation is converted to electrical energy by disassociating electrons from their nuclei in the absorber material
Implementation Method 2
Doping the CdTe absorber layer with specific proportions of copper (Cu) and silver (Ag) as co-dopants
Data Source
AI summary
A doped photovoltaic device is presented. The photovoltaic device includes a semiconductor absorber layer or stack disposed between a front contact and a back contact. The absorber layer comprises cadmium, selenium, and tellurium doped with Ag, and optionally with Cu. The Ag dopant may be added to the absorber in amounts ranging from 5×1015/cm3 to 2.5×1017/cm3 via any of several methods of application before, during, or after deposition of the absorber layer. The photovoltaic device has improved Fill Factor and PMAX at higher Pr(=Isc*Voc product) values, e.g. about 160 W, which results in improved conversion efficiency compared to a device not doped with Ag. Improved PT may result from increased Isc, increased Voc, or both.