Semiconductor Upconversion System with Band Offset
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Solution Overview
Problem
Existing photovoltaic systems face inefficiencies in photon upconversion, with low probabilities and energies in current methods, limiting their ability to displace fossil fuels and reduce costs effectively.
Innovation Solution
A system comprising semiconductor materials with controlled valence and conduction band offsets and discrete energy states, combined with graded compositions, is used to suppress radiative and nonradiative loss mechanisms, maximizing the probability of upconverting two lower-energy photons into a single higher-energy photon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional upconversion methods (nonlinear frequency doubling, Auger processes, lanthanide-doped materials) are used, then upconversion can occur, but the probability of upconversion is extremely low and photon energy efficiency is very low
Solution Approach 1:
The patent changes the energy level parameters by introducing an intermediate state positioned between the ground state and the final excited state. This intermediate state is engineered with specific energy levels that allow sequential photon absorption while minimizing energy loss through radiative and non-radiative pathways, thereby simultaneously improving upconversion probability and photon energy efficiency
Solution Approach 2:
The patent introduces an intermediate quantum state as a mediator in the upconversion process. This intermediate state acts as a stepping stone that facilitates the transition from ground state to final excited state through two sequential photon absorptions, enabling efficient energy transfer while suppressing direct radiative recombination losses
2Device complexity
If single quantum dot materials are used for upconversion, then material simplicity is maintained, but there is no path to achieving high upconversion probability
Solution Approach 1:
The patent employs composite quantum dot structures with multiple semiconductor materials (e.g., CdSe core with ZnS shell, or type-II heterostructures like CdTe/CdSe) that combine different band structures to create the desired intermediate state. This composite approach enables high upconversion probability while maintaining relatively simple colloidal synthesis processes
Solution Approach 2:
The patent segments the quantum dot structure into distinct regions (core/shell or type-II heterostructure) with different materials and band structures. This segmentation allows independent optimization of each region's properties to achieve the desired intermediate energy state and improve upconversion probability
3Ease of manufacture
If less-expensive PV device technologies are used, then module cost is reduced, but land costs and balance-of-systems costs may increase
Solution Approach 1:
The patent changes the optical parameters of the PV system by integrating upconversion quantum dots that convert sub-bandgap photons into usable higher-energy photons. This parameter change enables lower-cost PV materials to achieve higher effective utilization of the solar spectrum, improving energy efficiency per land area without sacrificing manufacturing simplicity
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 enhances the net upconversion efficiency by minimizing energy loss pathways and optimizing the emission of high-energy photons, potentially reducing the cost and increasing the efficiency of photovoltaic systems.
Implementation Method 1
Photon upconversion (UC) is a process in which the sequential absorption of two or more lower-energy photons leads to the emission of a single photon with higher energy than any of the absorbed photons
Implementation Method 2
Efficient photon upconversion requires the use of discrete quantum states to suppress both radiative and nonradiative loss pathways
Data Source
AI summary
Described herein are materials and systems for efficient upconversion of photons. The materials may be disposed in a system comprising two semiconductor materials with an interface therebetween, the interface comprising a valence and/or conduction band offset between the semiconducting materials of about −0.5 eV to about 0.5 eV, including 0, wherein one of the semiconductor materials is a material with discrete energy states and the other is a material with a graded composition and/or controlled band gap. The system can upconvert photons by: a) controlling energy levels of discrete energy states of a semiconducting material in a system to direct tunneling and exciton separation; b) controlling a compositional profile of another semiconducting material in the system to funnel charges away from an upconversion region and into a recombination zone; and c) utilizing the discrete energy states of the semiconducting material in the system to inhibit phonon relaxation.