Bragg Reflector Solar Cell Current Generation
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Solution Overview
Problem
Conventional multijunction solar cells face efficiency limitations due to metallic electrodes blocking solar energy and heat dissipation as resistive loss, which reduces performance, especially in high-power devices, and low-current-producing layers in these cells can limit the entire stack's current output.
Innovation Solution
Incorporating a distributed Bragg reflector structure beneath the nitride layer to reflect longer wavelengths back into the solar cell, increasing absorption and reducing heat dissipation by reflecting unused radiation, thereby enhancing current generation and collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional multijunction solar cells are designed to optimize solar to electrical energy conversion, then efficiency is improved, but metallic electrodes block solar energy and cause heat dissipation as resistive loss
Solution Approach 1:
A distributed Bragg reflector (DBR) structure is introduced as an intermediary component between the solar cell and the underlying layer. The DBR consists of alternating layers of materials with different refractive indices, creating constructive interference for specific wavelength ranges to reflect photons back into the solar cell absorber, thereby reducing energy loss from transmission and improving overall energy conversion efficiency
Solution Approach 2:
The patent optimizes the thickness and refractive index parameters of the DBR layers to achieve maximum reflectivity for specific wavelength ranges. By carefully controlling the optical parameters (layer thickness, refractive index contrast), the system achieves enhanced photon reflection and reduced energy loss while maintaining electrical performance
2Loss of energy
If the solar cell absorber layer is made thinner to reduce resistive loss, then heat dissipation is reduced, but current generation decreases due to lower absorption
Solution Approach 1:
The distributed Bragg reflector acts as an optical intermediary that compensates for the reduced absorption in thinner absorber layers by reflecting unabsorbed photons back into the active region, enabling the system to maintain high current generation while using thinner layers that produce less resistive heating
Solution Approach 2:
The DBR structure enables continuous photon interaction with the absorber layer by reflecting photons that would otherwise be transmitted through the thin absorber. This creates multiple passes of photons through the absorber material, ensuring continuous energy absorption and current generation despite the reduced thickness
3Adaptability or versatility
If dilute nitride layers are used to achieve desired bandgap, then spectral matching is improved, but current production is weak due to low absorption coefficient
Solution Approach 1:
The distributed Bragg reflector serves as an optical mediator that enhances the interaction between photons and the dilute nitride absorber layer. By reflecting photons back into the absorber, the DBR compensates for the low absorption coefficient of dilute nitride materials, enabling these materials to achieve both desired spectral matching and adequate current production
Solution Approach 2:
The periodic structure of the DBR with alternating high and low refractive index layers creates constructive interference for specific wavelength ranges. This periodic optical action enhances photon reflection and increases the effective path length of photons through the dilute nitride absorber, improving current generation while maintaining spectral matching
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 significantly increases current density and efficiency in solar cells with low absorption coefficients or minority-carrier collection probability, making them more cost-effective and suitable for high-power applications.
Implementation Method 1
the first Bragg reflector is operable to reflect a first range of radiation wavelengths back into the first solar cell and the second Bragg reflector operable to reflect a third range of wavelengths back into the first solar cell
Implementation Method 2
the first Bragg reflector and the second Bragg reflector are operable to cool the solar cell device by reflecting a second range of radiation wavelengths that are outside the photogeneration wavelength range of the first solar cell or that are weakly absorbed
Implementation Method 3
the first solar cell comprises a dilute nitride composition and has a first bandgap
Data Source
AI summary
The present disclosure generally relates to a solar cell device that a first Bragg reflector disposed below a first solar cell and a second Bragg reflector disposed below the first Bragg reflector, wherein the first solar cell comprises a dilute nitride composition and has a first bandgap, wherein the first Bragg reflector is operable to reflect a first range of radiation wavelengths back into the first solar cell and the second Bragg reflector is operable to reflect a third range of wavelengths back into the first solar cell, and the first Bragg reflector and the second Bragg reflector are operable to cool the solar cell device by reflecting a second range of radiation wavelengths that are outside the photogeneration wavelength range of the first solar cell or that are weakly absorbed by the first solar cell.