Double-Junction Photovoltaic Device for Reduced Carrier Recombination
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Solution Overview
Problem
Conventional single p-n junction photovoltaic cells have low conversion efficiencies due to rapid recombination of electrons and holes, limiting the contribution of absorbed photons to photo-current.
Innovation Solution
A photovoltaic device with double junctions is designed, featuring a substrate with multiple doped regions of varying polarity and concentration, creating a larger depletion region for enhanced light absorption and reduced recombination, with electrodes formed on these regions to facilitate charge separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single p-n junction is used in photovoltaic cells, then the device structure is simple, but the conversion efficiency is low due to rapid electron-hole recombination
Solution Approach 1:
The single p-n junction is segmented into multiple junctions (first p-n junction between P-type substrate and N-type well, second p-n junction between N-type well and P-type region). This segmentation creates multiple depletion regions that work together to reduce carrier recombination while maintaining manufacturing feasibility through sequential doping processes
Solution Approach 2:
Different regions are doped with different doping concentrations to create localized properties: the P-type substrate has a first doping concentration, the N-type well has a second doping concentration, and the P-type region has a third doping concentration. This local quality variation optimizes charge separation and collection at each interface, improving overall conversion efficiency
2Productivity
If multiple doped regions with varying concentrations are introduced to reduce recombination, then conversion efficiency improves, but device complexity increases
Solution Approach 1:
The doping structures are nested within each other: the N-type well is formed within the P-type substrate, and the P-type region is formed within the N-type well. This nested configuration creates multiple junctions in a compact arrangement, improving conversion efficiency without proportionally increasing device complexity
Solution Approach 2:
The invention transitions from a single-planar junction to a multi-layer vertical structure with doped regions at different depths and concentrations. This dimensional arrangement allows multiple junctions to be stacked vertically, reducing lateral complexity while improving efficiency through enhanced light absorption and charge separation
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 double junction configuration increases the surface area for light absorption and reduces electron-hole recombination, leading to higher conversion efficiencies compared to single junction devices.
Implementation Method 1
A photovoltaic cell is a solid state device that converts the energy of sunlight into electricity by the photovoltaic effect
Implementation Method 2
As sunlight shines on the single p-n junction from the front side of the substrate 510, electrons in the semiconductor may absorb the light and be excited into the conduction band
Data Source
AI summary
The present invention, a photovoltaic device includes a substrate having a first doped-type, a first doped region having a second doped-type in the substrate, a second doped region in a portion of the first doped region and exposing the other portion of the first doped region, and a third doped region in the exposed portion of the first doped region. The polarity of the second doped-type is substantially reversed with that of the first doped-type. The second doped region has a polarity substantially identical to that of the first doped-type and a doped concentration substantially greater than that of the substrate. The third doped region has a polarity substantially identical to that of the second doped-type and a doped concentration substantially greater than that of the first doped region. The first doped-type is one of N-type and P-type, while the second doped-type is the other of P-type and N-type.