Photon-Confinement Solar Cell Structure for Photon Recycling

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Solution Overview

Problem

Single-junction solar cells are limited by the Shockley-Queisser model, which constrains their efficiency due to radiative and non-radiative recombination losses, preventing them from reaching their ultimate efficiency limits.

Innovation Solution

A photonically-confined solar cell model is proposed, which reduces the probability of photon escape through structural designs such as bandpass reflectors and perfect reflectors, effectively suppressing radiative and non-radiative recombination losses, thereby increasing the open-circuit voltage and fill factor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If single-junction solar cells are designed to maximize light absorption, then photocurrent increases, but radiative recombination losses increase and open-circuit voltage is limited below the bandgap

Engineering Contradiction:

Improvepower conversion efficiencyVSAvoidradiative recombination losses

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent converts the harmful radiative recombination losses into beneficial photon recycling. By designing optical confinement structures (reflectors, waveguides) that trap emitted photons within the active layer, previously lost radiative recombination events are converted into additional electron-hole pair generation, transforming energy loss into useful photocurrent while maintaining high open-circuit voltage

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent introduces optical confinement in the vertical dimension through layered reflector structures and waveguide modes, creating photon recycling pathways that extend the photon lifetime within the device. This dimensional approach to photon management enables sustained light-matter interaction that simultaneously enhances both current and voltage

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Ease of manufacture

If photon escape probability is increased to simplify device structure, then manufacturing is easier, but energy conversion efficiency decreases due to photon losses

Engineering Contradiction:

Improvedevice structure simplicityVSAvoidphoton escape losses

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent introduces optical intermediaries (dielectric mirrors, metal reflectors, waveguide layers) that mediate between the active layer and external environment. These intermediary structures selectively manage photon escape - allowing unwanted photons to escape while trapping and recycling useful photons - thereby decoupling the simplicity of manufacturing from the requirement for high efficiency

Inventive Principle:

Principle #24Intermediary (Mediator)

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 potentially surpasses the efficiency limits predicted by the Shockley-Queisser model, enabling higher power conversion efficiency and broader research horizons for simple, low-cost, high-efficiency single-junction solar cells.

Implementation Method 1

a solar cell whose device operation fully or partly follows the photon confinement model is defined as a photonically-confined solar cell (PCSC)

Methodology Applied

Scientific EffectPhotovoltaic effect: Photovoltaic Effect

Implementation Method 2

determining a photocurrent density of the solar cell generated by a standard AM1.5G solar spectral irradiance

Methodology Applied

Scientific EffectPhoton absorption: Absorption (EM radiation)

Implementation Method 3

Photon confinement structures are provided on the surfaces and edges of the solar cell to effectively reduce the probability of photons escaping from the cell

Methodology Applied

Scientific EffectPhoton confinement:

Implementation Method 4

Photon confinement structures are provided on the surfaces and edges of the solar cell to effectively reduce the probability of photons escaping

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS12032881B2Photovoltaic and optoelectronic devices based on photon confinement effect

Publication Date: 2024.07.09 ZHEJIANG UNIV

AI summary

A photon confinement theoretical model is proposed, and a solar cell structure model is designed based on the theoretical model, thereby providing a photonically-confined solar cell and optoelectronic device to effectively reduce the probability of photons escaping from the cell. The theoretical model is established by the following steps: obtaining a relationship between a photocurrent density and an incident photon energy; obtaining a relationship between a radiative recombination photocurrent density and the incident photon energy; determining a relationship between the radiative recombination photocurrent density and a total recombination photocurrent density; obtaining a relationship between the photocurrent density generated by the standard spectral irradiance, the total recombination photocurrent density and an external current density of the solar cell; obtaining an output open-circuit voltage of the cell; obtaining an output short-circuit current density of the cell; obtaining a fill factor (FF); and obtaining a maximum power conversion efficiency (PCE).