Solar Cell Inducing Layer High Surface Charge Density
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Solution Overview
Problem
Conventional solar cells with inversion or accumulation layers suffer from limited lateral conductivity and inadequate surface passivation, particularly on non-crystalline surfaces, due to the use of materials like silicon nitride which only achieve small charge carrier inversion or accumulation.
Innovation Solution
A solar cell design that utilizes an inducing layer with a high surface charge density of at least 10^12 cm^-2, preferably 10^13 cm^-2, to induce inversion or accumulation layers with enhanced lateral conductivity and improved surface passivation, using materials like aluminium fluoride (AlF3) or aluminium oxide (Al2O3), which can be applied via atomic layer deposition (ALD) to ensure even coverage and precise thickness control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional materials like silicon nitride are used to produce inversion or accumulation layers, then surface passivation is achieved, but lateral conductivity remains limited and charge carrier inversion/accumulation is small
Solution Approach 1:
The patent applies parameter changes by increasing the surface charge density of the inducing layer from conventional levels (5-7 x 10^12 cm^-2 for SiNx) to at least 10^13 cm^-2. This parameter change enables both adequate surface passivation and sufficient lateral conductivity, resolving the technical contradiction between these two requirements.
2Ease of manufacture
If the inducing layer is applied directly on the semiconductor layer, then processing requirements are reduced, but surface passivation may be inadequate on non-crystalline surfaces
Solution Approach 1:
The patent resolves this contradiction by changing the surface charge density parameter to at least 10^13 cm^-2, which provides sufficient passivation effect even when the inducing layer is applied directly on the semiconductor layer, thereby reducing processing requirements while maintaining reliable surface passivation.
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 high surface charge density inducing layers significantly increase lateral conductivity and enhance surface passivation, minimizing ohmic losses and improving the overall performance of solar cells, especially as semiconductor wafers become thinner.
Implementation Method 1
Due to the positive surface charge density of the SiNx-layer, in a surface region of the semiconductor layer, depending on the doping of the semiconductor layer, an inversion layer or an accumulation layer is produced
Implementation Method 2
additional majority charge carriers are drawn to the surface region in order to form an accumulation layer
Implementation Method 3
minority charge carriers are drawn in while majority charge carriers are pushed away from the surface region in order to achieve a charge carrier inversion
Implementation Method 4
As a result of the formation of the inversion layer or accumulation layer at the same time passivation of the semiconductor surface is achieved, because, as a result of pushing away a charge carrier type, charge carrier recombination at surface defects is reduced
Data Source
AI summary
A solar cell comprising a semiconductor layer (1) with first doping, an inducing layer (3) arranged on the semiconductor layer (1) and an inversion layer (4) or accumulation layer (4) which due to the inducing layer (3) is induced underneath the inducing layer (3) in the semiconductor layer (1) is characterised in that the inducing layer (3) comprises a material with a surface charge density of at least 1012 cm-2, preferably of at least 5x1012 cm-2, more preferably of at least 1013 cm-2.