Passivated Photovoltaic Cell Edge Coating to Prevent TCO Short-Circuits
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Solution Overview
Problem
Photovoltaic cells with passivated contacts face challenges in avoiding short-circuits between p- and n-doped parts while maximizing minority charge collection and minimizing optical losses, particularly due to incomplete coverage with transparent conductive oxide (TCO) layers, which affects performance and leads to edge-related issues.
Innovation Solution
A photovoltaic cell design featuring passivation layers on main and lateral faces, with strategically placed conductive transparent oxide layers and non-reflective coatings to ensure complete coverage of the rear face and partial coverage of the front face, avoiding short-circuits and optimizing charge collection, and incorporating a non-reflective coating to mitigate optical losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the front face of the cell is completely covered with TCO layer, then non-reflective performance is improved, but short-circuits occur between front and rear faces through lateral overlap
Solution Approach 1:
The TCO layer deposition is segmented into two distinct operations: first, the front face is covered with TCO while leaving lateral edges exposed; second, the rear face is covered with TCO. This segmentation prevents lateral overlap and short-circuits while maintaining non-reflective performance on both main faces.
Solution Approach 2:
The solution moves from a two-dimensional planar coverage problem to a three-dimensional spatial arrangement by carefully controlling the lateral boundaries of TCO deposition. The front TCO layer is deposited only on the front main face without extending to lateral edges, creating a spatial separation that prevents short-circuits while maintaining optical performance.
2Reliability
If the rear face edges are masked to prevent TCO overlap, then short-circuits are avoided, but part of the rear face remains uncovered reducing cell performance
Solution Approach 1:
The masking step is completely removed from the process. Instead of using masks to prevent TCO overlap, the invention extracts the masking function by precisely controlling the deposition process to deposit TCO only on the rear main face without lateral extension, eliminating the need for masks and their associated performance losses.
3Productivity
If TCO layers are deposited on both front and rear faces without lateral coverage control, then charge collection is maximized, but short-circuits occur between p- and n-doped parts
Solution Approach 1:
Different regions of the cell are given different TCO coverage qualities: the front main face receives complete TCO coverage for optimal non-reflective performance and charge collection, the rear main face receives complete TCO coverage for charge collection, while the lateral edges are deliberately left uncovered to prevent short-circuits. This local differentiation resolves the contradiction between charge collection and short-circuit prevention.
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 solution effectively prevents short-circuits, maximizes minority charge collection, and reduces optical losses by ensuring comprehensive coverage with TCO layers and utilizing non-reflective coatings to confine light, thereby enhancing the overall performance of the photovoltaic cell.
Implementation Method 1
a non-reflective coating at least partially covering second parts of the first charge-collecting layer and/or of the second charge-collecting layer disposed on the lateral faces of the substrate and not covered with the second layer of conductive transparent oxide, and also covering the edges of the first main face
Implementation Method 2
A cell with passivated contacts includes one or more thin layers interposed between the metallisations and the absorber and which make it possible to avoid direct contact between the metallisations and the absorber. This makes it possible to greatly limit recombinations of charge carriers generated under illumination
Implementation Method 3
These layers serve both as non-reflective layers and layers for lateral transport of the charges, in particular on the face collecting minority carriers
Implementation Method 4
Photovoltaic cells with passivated contacts face challenges in avoiding short-circuits between p- and n-doped parts while maximizing minority charge collection
Data Source
AI summary
Photovoltaic cell comprising, an assembly comprising a substrate, first and second passivation layers covering opposite faces of the substrate and also lateral faces of the substrate, and first and second charge-collecting layers; a first layer of TCO disposed against the first main face of the assembly and such that edges of the first main face of the assembly are not covered by the first layer of TCO; a second layer of TCO covering the whole of the second main face of the assembly; a non-reflective coating partly covering the first and/or second charge-collecting layers on the lateral faces of the substrate and not covered by the second layer of TCO, and also covering the edges of the first main face.