MBE CdTe Solar Cell In Situ Doping
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Solution Overview
Problem
Current photovoltaic cells, particularly cadmium telluride (CdTe) thin film solar cells, face challenges in achieving high conversion efficiency and low production costs due to limitations in doping capabilities and interface quality, leading to reduced electrical current and device performance.
Innovation Solution
The development of a molecular beam epitaxy (MBE) process for forming high-performance polycrystalline CdTe thin film solar cells with in situ doping, compositional grading, and grain boundary passivation, allowing for precise control over layer thickness and deposition rates, which eliminates the need for a CdS 'window' layer and enhances the efficiency of the p-n junction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional photovoltaic cell manufacturing processes are used, then production costs are reduced, but conversion efficiency and device performance deteriorate
Solution Approach 1:
The patent applies parameter changes by implementing in situ doping during the MBE deposition process to achieve precise control over dopant concentration and distribution. This enables optimization of the p-n junction properties and grain boundary passivation, directly improving conversion efficiency while maintaining cost-effectiveness through a single-step process
Solution Approach 2:
The patent employs preliminary action by performing in situ doping and compositional grading during the deposition process itself, rather than requiring subsequent separate processing steps. This preliminary doping action during deposition improves interface quality and grain boundary passivation before the cell is completed, enhancing performance without adding manufacturing complexity
2Reliability
If in situ doping and compositional grading are implemented, then device performance and grain size are improved, but process complexity increases
Solution Approach 1:
The patent merges multiple functions into the single MBE deposition process: layer formation, in situ doping, compositional grading, and grain boundary passivation all occur simultaneously during one continuous deposition process. This consolidation improves device performance through better interface quality while avoiding the complexity of multiple separate processing steps
Solution Approach 2:
The MBE process is made multi-functional by enabling it to perform deposition, doping, and compositional control in a single operation. The system universally handles both the structural formation and the electrical property optimization, reducing the need for additional specialized equipment and process steps
3Productivity
If high deposition rate polycrystalline growth is used, then productivity increases, but layer thickness control precision may deteriorate
Solution Approach 1:
The patent implements feedback control through real-time monitoring of deposition rate and in-situ measurement techniques during the MBE process. This allows dynamic adjustment of deposition parameters to maintain precise layer thickness control even at high deposition rates, ensuring both productivity and 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
This approach results in solar cells with improved short circuit current, open circuit voltage, and fill factor, achieving power efficiencies between 18% and 28%, and enables the production of high-quality thin film solar cells with longer lifetimes and larger grain sizes, reducing production costs.
Implementation Method 1
high deposition rate polycrystalline growth using molecular beam epitaxy (MBE)
Implementation Method 2
successive layers of which provide, in sequence: an optional thin buffer layer; a low ohmic, very high doped frontside connection layer
Implementation Method 3
A photovoltaic cell is able to absorb radiant light energy and convert it directly into electrical energy
Implementation Method 4
in situ thermal anneal
Data Source
AI summary
Solar cell structures formed using molecular beam epitaxy (MBE) that can achieve improved power efficiencies in relation to prior art thin film solar cell structures are provided. A reverse p-n junction solar cell device and methods for forming the reverse p-n junction solar cell device using MBE are described. A variety of n-p junction and reverse p-n junction solar cell devices and related methods of manufacturing are provided. N-intrinsic-p junction and reverse p-intrinsic-n junction solar cell devices are also described.