Multi-Band Gap Silicon Photovoltaic Cell Structure
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Solution Overview
Problem
Conventional silicon-based solar cells face limitations in efficiency due to single band gap structures, leading to heat generation from photons with energies above the band gap, and multi-junction cells suffer from junction loss and lattice mismatch, restricting photovoltaic conversion efficiency.
Innovation Solution
A photovoltaic cell with a multi-band gap structure is created using silicon nanocrystals embedded in a silicon-rich dielectric layer, formed by laser-annealing a silicon-rich dielectric layer to produce nanocrystals with sizes ranging from 1-20 nm, allowing for enhanced light absorption across a wider spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single band gap silicon structure is used, then the device complexity is low, but the photovoltaic conversion efficiency is limited due to heat generation from high energy photons
Solution Approach 1:
The photovoltaic cell is segmented into multiple layers with different band gap materials (amorphous silicon layer with band gap 1.7-2.0 eV, crystalline silicon layer with band gap 1.1 eV) to handle different photon energy ranges separately, reducing energy loss while maintaining manageable structural complexity
Solution Approach 2:
The invention uses a composite structure combining amorphous silicon and crystalline silicon layers, each with different optical and electrical properties, to simultaneously capture high energy and low energy photons efficiently, improving overall energy utilization without excessive complexity
2Loss of energy
If multi-junction cells are used to improve photovoltaic efficiency, then the energy conversion is improved, but junction loss and lattice mismatch occur
Solution Approach 1:
The invention applies local quality by having the amorphous silicon layer specifically targeted at absorbing high energy photons (blue and UV regions) while the crystalline silicon layer handles lower energy photons, with each layer optimized for its specific function to avoid the pitfalls of conventional multi-junction cells
Solution Approach 2:
The amorphous silicon layer acts as an intermediary that absorbs high energy photons before they reach the crystalline silicon layer, preventing junction losses and lattice mismatch issues by creating a gradual transition in band gap rather than abrupt junctions
3Loss of energy
If conventional silicon solar cells are used, then the manufacturing is straightforward, but the conversion efficiency is limited to about 33%
Solution Approach 1:
The amorphous silicon layer is deposited first as a preliminary action to capture high energy photons, creating an optimized foundation for the subsequent crystalline silicon layer, which improves overall efficiency while following a systematic manufacturing sequence
Solution Approach 2:
The invention changes the optical parameter (band gap) by using different silicon phases with different band gaps (1.7-2.0 eV for amorphous, 1.1 eV for crystalline) to expand the absorbable solar spectrum, achieving higher efficiency with modified but still compatible manufacturing parameters
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 multi-band gap structure improves photovoltaic conversion efficiency by effectively utilizing a broader range of solar spectrum energies, reducing heat generation and increasing electrical energy output compared to single band gap cells, while avoiding the drawbacks of multi-junction cells.
Implementation Method 1
formed by laser-annealing a silicon-rich dielectric layer to produce nanocrystals
Implementation Method 2
laser-annealing a silicon-rich dielectric layer to produce nanocrystals with sizes ranging from 1-20 nm
Implementation Method 3
A solar cell or photovoltaic cell is a semiconductor device that converts solar/optical energy of light into electrical power by the photovoltaic effect
Implementation Method 4
When a photon hits the solar cell, the photon can pass straight through the silicon if it has lower photon energy, or reflect off the surface, or be absorbed by the silicon if it has photon energy higher than the silicon band gap value
Data Source
AI summary
One aspect of the present invention relates to a photovoltaic cell. In one embodiment, the photovoltaic cell includes a first conductive layer, an N-doped semiconductor layer formed on the first conductive layer, a first silicon layer formed on the N-doped semiconductor layer, a nanocrystalline silicon (nc-Si) layer formed on a first silicon layer, a second silicon layer formed on the nc-Si layer, a P-doped semiconductor layer on the second silicon layer, and a second conductive layer formed on the P-doped semiconductor layer, where one of the first silicon layer and the second silicon layer is formed of amorphous silicon, and the other of the first silicon layer and the second silicon layer formed of polycrystalline silicon.