Tandem Solar Cell Recombination Layer for Shunt Path Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional tandem solar cells face efficiency limitations due to shunt paths and optical losses in the recombination layer, which are caused by low horizontal resistance and high absorption in the visible and near-infrared ranges, leading to reduced electron mobility and recombination efficiency.
Innovation Solution
A tandem solar cell design using a recombination layer composed of ITO with a specific ratio of SnO2 to In2O3 (18:79 to 21:82) to increase horizontal resistance, reduce electrical conductivity, and minimize electron mobility, thereby reducing shunt paths and optical losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional transparent conductive thin films (ITO with 10 wt% SnO2) are used as recombination layers, then electrical conductivity is high and electrons can be moved efficiently, but shunt paths are created and electrical loss occurs
Solution Approach 1:
The patent changes the compositional parameters of the transparent conductive thin film by adjusting the SnO2 content from conventional 10 wt% to a range of 5-15 wt%, and controls the thickness between 50-200 nm. This parameter optimization balances electrical conductivity with horizontal resistance, preventing shunt paths while maintaining efficient electron transport. The specific parameter range resolves the contradiction by finding the optimal point where electrical loss is minimized without creating shunt paths.
2Loss of energy
If ITO with 10 wt% SnO2 is used as transparent conductive thin film, then electrical conductivity is high, but optical absorption increases in visible and near-infrared ranges
Solution Approach 1:
The patent optimizes the SnO2 content parameter to 5-15 wt% and thickness to 50-200 nm, which reduces optical absorption in the visible and near-infrared ranges while maintaining adequate electrical conductivity. This parameter adjustment resolves the contradiction by reducing free carrier concentration to minimize optical loss while preserving sufficient electrical conductivity for electron transport.
3Speed
If free charge concentration is increased in transparent conductive thin films, then mobility of free charges increases to some extent, but scattering between free charges and ionized impurities occurs, resulting in decreased mobility
Solution Approach 1:
The patent optimizes the SnO2 doping concentration to 5-15 wt%, which controls the free charge concentration at an optimal level. This prevents excessive ionized impurities that cause scattering while maintaining sufficient free charges for adequate mobility. The optimized parameter range resolves the contradiction by avoiding both too low and too high free charge concentrations.
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 proposed design minimizes efficiency loss by preventing shunt paths and reducing electron mobility restrictions, while maintaining low absorption in the short wavelength range, thereby improving current value and overall efficiency.
Implementation Method 1
the horizontal resistance of a recombination layer connecting the upper and lower cells of a tandem solar cell can be reduced to minimize the occurrence of a shunt path
Implementation Method 2
thereby reducing the recombination efficiency due to electron transfer problems
Implementation Method 3
there is a problem in that a tandem solar cell having a structure in which the upper cell with a large band gap absorbs solar energy in a low wavelength range and the lower cell with a low band gap absorbs solar energy in a high wavelength range has limitations in reducing optical loss
Implementation Method 4
when the concentration of free charges is low, grain boundary scattering caused by the energy barrier (potential barrier) formed by free charges trapped at grain boundaries plays a significant role
Implementation Method 5
grain boundary scattering caused by the energy barrier (potential barrier) formed by free charges trapped at grain boundaries
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention provides a tandem solar cell and a manufacturing method therefor. The tandem solar cell can increase horizontal resistance of a recombination layer connecting upper and lower cells of a tandem solar cell to minimize shunt path from being created, thereby preventing a drop in recombination efficiency due the problem of electron transfer, and can increase current value when applied to tandem-type solar cells due to low absorption in the short wavelength range.