Core-Shell Nanowire Solar Cell Exceeding Shockley-Queisser Limit
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Solution Overview
Problem
Current single-junction silicon solar cells are limited by the Shockley-Queisser limit, achieving efficiencies of up to 29% due to energy loss to heat from photons exceeding the bandgap energy, and existing techniques such as multi-exciton generation and avalanche multiplication are either ineffective or impractical for achieving higher efficiencies.
Innovation Solution
The development of optical-to-electrical energy conversion devices using core-shell nanostructures with heavily compensated p/n junctions, employing a cascaded exciton ionization mechanism that generates multiple electron-hole pairs from a single photon, allowing for efficient absorption of photons at various wavelengths and exceeding the Shockley-Queisser efficiency limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If single-junction silicon solar cells are used, then manufacturing simplicity is maintained, but energy conversion efficiency is limited to 29% due to Shockley-Queisser limit
Solution Approach 1:
The patent applies local quality by creating core-shell nanostructures with different doping types (p-type core, n-type shell) within the silicon substrate. This localized differentiation enables cascaded exciton ionization at the core-shell interface, allowing multiple electron-hole pair generation from single photons while maintaining overall device simplicity and single-junction architecture.
Solution Approach 2:
The invention uses composite materials by combining differently doped semiconductor regions (p-type and n-type) in a core-shell configuration within the silicon substrate. This composite structure enables the cascaded exciton ionization mechanism, achieving over 48% conversion efficiency while remaining within single-junction silicon technology.
2Productivity
If multi-exciton generation or avalanche multiplication techniques are employed, then energy conversion efficiency may exceed Shockley-Queisser limit, but device complexity and impracticality increase
Solution Approach 1:
The patent implements self-service through the cascaded exciton ionization mechanism, where photogenerated carriers automatically generate additional electron-hole pairs through impact ionization at the core-shell interface without requiring external control systems or complex multi-stage structures. The process is self-sustaining within the single-junction device.
Solution Approach 2:
The invention changes key parameters by introducing heavily doped p-n junctions at the core-shell interface with specific doping concentrations (10^19-10^21 atoms/cm³). This parameter modification enables the cascaded exciton ionization process, achieving high efficiency without the complexity of multi-junction or avalanche structures.
3Power
If photons with energy exceeding bandgap are absorbed, then electrical signal generation is enabled, but energy loss to heat occurs
Solution Approach 1:
The patent converts the harmful energy loss to heat into a beneficial effect by utilizing hot carriers generated from high-energy photon absorption. These hot carriers drive cascaded impact ionization at the core-shell interface, generating multiple electron-hole pairs. The excess photon energy that would normally be wasted as heat is instead harnessed to create additional electrical charge carriers.
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
This approach achieves energy conversion efficiencies greater than 48% in single-junction Si solar cells, nearly doubling the theoretical limit, with the cascaded exciton ionization mechanism enabling high efficiency optoelectronic applications without the constraints of MEG or avalanche multiplication.
Implementation Method 1
generating an electrical signal from the light obtained by said optical-to-energy conversion via a cascaded exciton ionization (CEI) mechanism at the array of multilayered nanostructures
Implementation Method 2
Techniques, systems, and devices are described for highly-efficient optical to electrical energy conversion, e.g., which exceed the highest efficiencies achievable for single-junction Si according to Shockley-Queisser theory
Data Source
Figure 1~2C
Figure 2D
Figure 3
AI summary
Methods, systems, and devices are disclosed for implementing high conversion efficiency solar cells. In one aspect, an optical-to-electrical energy conversion device includes a substrate formed of a doped semiconductor material and having a first region and a second region, an array of multilayered nanoscale structures protruding from the first region of the substrate, in which the nanoscale structures are formed of a first co-doped semiconductor material covered by a layer of a second co-doped semiconductor material forming a core-shell structure, the layer covering at least a portion of the doped semiconductor material of the substrate in the second region, and an electrode formed on the layer-covered portion of the substrate in the second region, in which the multilayered nanoscale structures provide an optical active region capable of absorbing photons from light at one or more wavelengths to generate an electrical signal presented at the electrode.