Unpatterned Fabry-Perot Cavity for Broadband Solar Absorption
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Solution Overview
Problem
Existing solar cells face limitations in achieving broad spectral bandwidth absorption due to the link between cavity-photon lifetime and resonant linewidth, restricting coherent-enhancement schemes to discrete wavelengths, which is not suitable for solar conversion applications.
Innovation Solution
The integration of a PIN-diode solar cell into an unpatterned asymmetric planar Fabry-Pérot cavity with an alignment-free optical arrangement that preconditions incident light to assign appropriate angles of incidence, enabling omni-resonance and continuous-wavelength coherent perfect absorption (CPA) across a broad spectral range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If coherent perfect absorption (CPA) is implemented in a traditional optical cavity, then absorption is achieved at discrete resonant wavelengths, but the bandwidth is restricted due to the link between cavity-photon lifetime and resonant linewidth
Solution Approach 1:
The patent introduces an alignment-free optical arrangement with angular dispersion that dynamically adjusts the angle of incidence for different wavelengths. This dynamic adjustment allows the system to maintain resonance conditions across a broad spectral range rather than at fixed discrete wavelengths, thereby extending the bandwidth while preserving absorption precision through the angular dispersion mechanism
Solution Approach 2:
The patent changes the parameter of angle of incidence as a function of wavelength through the alignment-free optical arrangement. By varying the angle of incidence across different wavelengths, the system overcomes the fixed resonant wavelength limitation of traditional CPA, enabling continuous wavelength absorption across a broad spectral bandwidth while maintaining the coherence required for perfect absorption
2Quantity of substance
If thin-film solar cells are used to reduce cost and weight, then material usage is reduced, but optical absorption diminishes due to reduced thickness
Solution Approach 1:
The patent employs coherent resonant optical effects that create standing wave patterns within the thin-film structure, effectively trapping light and increasing the interaction path length between photons and the absorptive material. This resonant enhancement compensates for the reduced material thickness, maintaining high optical absorption while using minimal material quantity
Solution Approach 2:
The patent creates a composite optical structure combining the thin-film solar cell with the alignment-free optical arrangement featuring angular dispersion. This composite system integrates the low-material-quantity advantage of thin films with the light-trapping capability of resonant optical structures, achieving both reduced material usage and maintained absorption performance
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 doubles the photocurrent in the near-infrared spectral range from 660-740 nm and ensures complete broadband optical absorption, overcoming the limitations of discrete wavelength absorption in traditional CPA schemes.
Implementation Method 1
A non-limiting embodiment is a PIN-diode solar cell... enabling a significant boost (e.g., up to 90%) of the photocurrent generated in an 80 nm NIR region
Implementation Method 2
coherent perfect absorption (CPA)... spectrally flat 100% absorption over a full octave of bandwidth in a 2 μm thick polycrystalline silicon film incorporated into a carefully designed planar cavity
Implementation Method 3
We introduce into the external field angular dispersion that is equal in magnitude but opposite in sign to that of the cavity. Consequently, angular dispersion cancellation allows all wavelengths within a selected band
Data Source
AI summary
A visibly transparent planar structure using a CPA scheme to boost the absorption of a multi-layer thin-film configuration, requiring no surface patterning, to overcome the intrinsic absorption limitation of the absorbing material. This is achieved in a multi-layer absorbing Fabry-Perot (FP) cavity, namely a thin-film amorphous silicon solar cell. Omni-resonance is achieved across a bandwidth of 80 nm in the near-infrared (NIR), thus increasing the effective absorption of the material, without modifying the material itself, enhancing it beyond its intrinsic absorption over a considerable spectral range. The apparatus achieved an increased external quantum efficiency (EQE) of 90% of the photocurrent generated in the 80 nm NIR region from 660 to 740 nm as compared to a bare solar cell. over the spectral range of interest.