Solar Cell Rear Electrode Design for Light Absorption
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Solution Overview
Problem
Conventional solar cells have reduced efficiency due to the formation of electrodes on both the light incident and non-incident surfaces of the substrate, which decreases the light incident area and hinders electron-hole pair collection.
Innovation Solution
A solar cell design featuring a semiconductor substrate of one conductive type, a second semiconductor layer of opposite conductive type, and electrodes positioned on the rear surface, with crystallinity-controlled layers such as a front passivation layer, emitter layers, and back surface field layers to minimize carrier loss and enhance light absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrodes are formed on both the light incident surface and non-incident surface of the substrate, then electron and hole collection is enabled, but the light incident area decreases and efficiency is reduced
Solution Approach 1:
The patent relocates electrodes from the light incident surface (2D plane) to the rear surface of the substrate, utilizing the third dimension (depth/thickness) of the solar cell structure. This dimensional shift allows the light incident surface to remain fully exposed while electrodes are positioned on the opposite surface, resolving the contradiction between electrode placement and light absorption area.
2Area of stationary object
If a back contact solar cell design is used with all electrodes on the rear surface, then light incident area is increased, but carrier loss may increase without proper passivation layers
Solution Approach 1:
The patent introduces intrinsic semiconductor layers and passivation layers as intermediary structures between the substrate and the rear surface electrodes. These intermediary layers serve dual functions: they provide electrical isolation to prevent carrier recombination (reducing energy loss) while allowing the rear surface electrode configuration to maintain maximum light incident area.
3Reliability
If crystallinity of semiconductor layers is increased, then carrier mobility is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent applies different crystallinity requirements to different regions and layers of the solar cell structure. The substrate maintains high crystallinity for optimal carrier mobility, while the emitter layer and passivation layers use lower crystallinity materials that are easier and cheaper to manufacture. This localized quality differentiation resolves the contradiction between performance and manufacturing complexity.
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 increases light absorption and reduces carrier loss, leading to improved solar cell efficiency by optimizing the crystallinity of layers and positioning electrodes on the rear surface, thereby enhancing the collection of electron-hole pairs.
Implementation Method 1
When light is incident on the solar cell, a plurality of electron-hole pairs are generated in the semiconductor. The electron-hole pairs are separated into electrons and holes by a photovoltaic effect.
Data Source
AI summary
A solar cell including a non-amorphous semiconductor substrate of a first conductive type; at least a first semiconductor layer on the non-amorphous semiconductor substrate, the first semiconductor layer including a portion that is amorphous and a plurality of portions having crystal lumps, so that the plurality of portions having the crystal lumps are distributed in the first semiconductor layer; a first electrode on the semiconductor substrate; and a second electrode on the semiconductor substrate.