Composite Light Harvesting Material for Photovoltaic Devices
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Solution Overview
Problem
Conventional solar cells are limited by the Shockley-Queisser limit, and existing strategies to exceed this limit face challenges in efficiently coupling organic and inorganic semiconductors for energy transfer, particularly in transferring triplet excitons.
Innovation Solution
A composite light harvesting material is developed that enables efficient Dexter energy transfer of triplet excitons from organic semiconductors to luminescent materials, which are resonant with the lowest optical absorption band, allowing for enhanced energy transfer and increased photocurrent in photovoltaic devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Förster resonance energy transfer is used to transfer singlet excitons from organic to inorganic semiconductors, then energy transfer can occur, but triplet exciton transfer is spin-forbidden and inefficient
Solution Approach 1:
The patent introduces a luminescent material as an intermediary between the organic semiconductor and inorganic semiconductor. The luminescent material receives triplet excitons from the organic semiconductor via Dexter energy transfer and then transfers energy to the inorganic semiconductor, mediating the energy transfer process and overcoming the spin-forbidden limitation of direct triplet exciton transfer to inorganic semiconductors
Solution Approach 2:
The patent replaces the inefficient spin-forbidden Förster resonance energy transfer mechanism with a two-step process involving Dexter energy transfer to the luminescent material followed by energy transfer to the inorganic semiconductor. This substitution of the energy transfer mechanism enables efficient triplet exciton utilization that was previously blocked by spin selection rules
2Productivity
If multiple exciton generation is achieved in organic semiconductors, then photocurrent can be doubled, but efficient coupling to inorganic semiconductors for energy transfer remains challenging
Solution Approach 1:
The luminescent material serves as a mediator that couples the organic semiconductor capable of multiple exciton generation with the inorganic semiconductor. It receives multiple triplet excitons from the organic semiconductor and efficiently transfers energy to the inorganic semiconductor, enabling reliable energy transfer coupling while maintaining the productivity benefit of doubled photocurrent generation
Solution Approach 2:
The patent creates a composite light harvesting material system comprising organic semiconductor, luminescent material, and inorganic semiconductor components. This composite structure enables both multiple exciton generation in the organic component and efficient energy transfer to the inorganic component, achieving both high productivity and reliable coupling
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 generated from high-energy photons while maintaining photovoltaic operation, overcoming the Shockley-Queisser limit by efficiently transferring triplet excitons to inorganic semiconductors, thereby improving solar cell efficiency.
Implementation Method 1
Visible photons are absorbed in pentacene to create singlet excitons, which undergo rapid exciton fission to produce pairs of triplets
Implementation Method 2
the triplet excitons can be transferred from the organic semiconductor to the luminescent material via Dexter energy transfer. The triplet excitons, formed as a result of multiple exciton generation in the organic semiconductor are transferred from the organic semiconductor to the luminescent material via non-radiative energy transfer
Implementation Method 3
the emitting chromophore emits some of the received energy at a wavelength that is red-shifted from the wavelength absorbed by the other chromophore
Data Source
Figure 1~2
Figure 3~4(d)
Figure 5(a)~5(d)
AI summary
A photovoltaic device comprising a light harvesting device and a photovoltaic cell; wherein the light harvesting device comprises an organic semiconductor photoactive layer capable of multiple exciton generation with a luminescent material dispersed therein; wherein the bandgap of the luminescent material is selected such that the triplet excitons, formed as a result from the multiple exciton generation in the organic semiconductor, can be transferred from the organic semiconductor into the luminescent material non-radiatively via Dexter Energy Transfer; a photovoltaic cell disposed in an emissive light path of the luminescent material and having a first photoactive layer, wherein the bandgap of the luminescent material matches or is higher than the bandgap of the first photoactive layer.