Amorphous Silicon Photovoltaic Cell Design for Carrier Collection
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Solution Overview
Problem
Photovoltaic cells with pn junctions between n-type single crystalline silicon substrates and p-type amorphous silicon films face reduced open voltages due to carrier recombination at interface states, leading to decreased photoelectric conversion efficiency, and existing solutions like HIT and BSF structures face issues with leak currents and incomplete carrier collection.
Innovation Solution
A photovoltaic cell design featuring a crystal-based semiconductor with intrinsic and conductivity-type amorphous semiconductor films, where the amorphous films are formed in specific regions and covered by translucent electrode layers to prevent recombination and leak currents, enhancing carrier collection and output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If amorphous silicon films are formed in the entire area of the main surface and back surface to improve carrier collection, then the collection factor is improved, but leak currents are generated due to film detour around side surfaces
Solution Approach 1:
The patent divides the amorphous silicon film formation into separate regions: the main surface area and the back surface area are treated independently with controlled lateral extension. The film on the main surface is prevented from laterally extending to the side surface, and the film on the back surface is similarly constrained, thereby segmenting the continuous film path that would otherwise create leak current paths through the side surface.
2Productivity
If amorphous silicon films are formed in the entire area to improve photoelectric conversion efficiency, then carrier collection is enhanced, but interface states cause carrier recombination
Solution Approach 1:
The patent introduces an intrinsic amorphous silicon film as an intermediary layer between the n-type single crystalline silicon substrate and the p-type amorphous silicon film. This intrinsic layer acts as a mediator that reduces the density of interface states at the junction, thereby minimizing carrier recombination losses while still allowing the p-type film to collect carriers effectively.
3Object-generated harmful factors
If the area of amorphous silicon film is reduced to prevent leak currents, then leak current is prevented, but carrier collection in peripheral regions is insufficient
Solution Approach 1:
The patent applies different film configuration strategies to different locations: on the main surface, the amorphous silicon film is formed with controlled lateral boundaries to prevent side surface contact, while on the back surface, the film is formed to cover the active area without extending to the side surface. This local quality differentiation ensures leak current prevention in critical areas while maintaining adequate carrier collection in functional areas.
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 design improves output characteristics by reducing carrier recombination at surface states and preventing leak currents, leading to increased short-circuit currents and fill factors, thus enhancing the overall photoelectric conversion efficiency.
Implementation Method 1
In the above-mentioned formation of the amorphous silicon film, a plasma CVD (Chemical Vapor Deposition) method has been generally used.
Implementation Method 2
an attempt to form an i-type amorphous silicon film and a p-type amorphous silicon film by the plasma CVD method
Implementation Method 3
The present invention relates to a photovoltaic cell using a semiconductor junction
Data Source
AI summary
In a photovoltaic cell, an i-type amorphous silicon film and an n-type amorphous silicon film are formed in a region excluding a predetermined width of an outer periphery on a main surface of an n-type single crystalline silicon substrate. A front electrode is formed so as to cover the i-type amorphous silicon film and the n-type amorphous silicon film on a main surface of the n-type single crystalline silicon substrate. An i-type amorphous silicon film and a p-type amorphous silicon film are formed on the entire area of a back surface of the n-type single crystalline silicon substrate. A back electrode is formed in a region excluding a predetermined width of an outer periphery on the p-type amorphous silicon film. A surface, on the side of the front electrode, of the photovoltaic cell is a primary light incidence surface.