Monolithic Blocking Diode in Triple-Junction PV Cells for Shadowing
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Solution Overview
Problem
Existing multi-junction photovoltaic (PV) solar cells are vulnerable to performance degradation when one or more cells are shadowed, leading to reverse bias and potential damage due to the absence of effective blocking diodes, which can short-circuit the entire system.
Innovation Solution
Integration of a monolithic blocking diode within the PV solar cell structure, providing electrical isolation and protection by using a trench between the PV solar cell stack and the blocking diode stack, ensuring that shadowed cells are protected and do not affect the overall circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If discrete external blocking diodes are used to protect PV solar cells from reverse bias damage, then reliability is improved, but device complexity increases
Solution Approach 1:
The blocking diode is merged with the PV solar cell to form an integrated monolithic structure. The diode is fabricated using the same semiconductor layers (Ge, GaAs, InGaP) as the solar cell, with the blocking diode stack sharing the substrate and some layers with the PV stack, eliminating the need for separate external blocking diodes and reducing overall device complexity while maintaining protection functionality
Solution Approach 2:
The blocking diode is nested within the PV solar cell structure itself. The diode is formed by selectively removing portions of the semiconductor layers and creating a p-n junction that is embedded within the multi-junction cell architecture, allowing the protection function to be contained within the solar cell boundary rather than requiring external components
2Power
If PV solar cells are connected in series to increase power output, then power delivery is improved, but vulnerability to shadowing increases
Solution Approach 1:
The blocking diode is pre-configured within each PV solar cell before operation. When shadowing occurs, the diode immediately activates to block reverse bias current, preventing the propagation of harmful effects to other cells in the series connection without requiring external intervention or additional circuitry
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 integrated monolithic blocking diode effectively prevents reverse bias and protects the solar cell circuit, maintaining power delivery to the load even when individual cells are shadowed, enhancing the reliability and efficiency of the PV system.
Implementation Method 1
When all PV solar cells are illuminated, a forward voltage bias is generated across each cell
Implementation Method 2
These discrete blocking diodes serve to protect their respective circuit of three PV solar cells when one or more PV solar cells are shadowed and stop producing energy
Data Source
AI summary
A multi-junction, photovoltaic (PV) solar cell with an integrated, monolithic blocking diode, and methods of fabrication, are disclosed. The integrated, monolithic blocking diode protects a circuit of PV solar cells when some PV solar cells are shadowed. A triple-junction PV solar cell includes a first conductive substrate with a PV solar cell stack and an adjacent blocking diode stack disposed on a common conductive substrate. A trench is located in between the two stacks, which provides electrical isolation. A triple-junction cell has: a Ge first PN junction, a GaAs second PN junction, and an InGaP third PN junction. A first metal contact is disposed on a portion of the PV solar cell stack, and a second metal contact is disposed completely across the blocking diode stack. Extraterrestrial satellites can use these triple-junction PV solar cells with integrated, monolithic blocking diodes.