Halogen-Substituted Small Molecule Semiconductors for Organic Solar Cells
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Solution Overview
Problem
There is a need for improved light harvesting molecules and molecular heterojunction devices that can efficiently absorb near-IR radiation, maximize open circuit voltages, and facilitate rapid and cheap generation of molecular libraries, while maintaining high charge carrier mobility and solution processability.
Innovation Solution
The development of non-polymeric semiconducting compounds with halogen-substituted benzothiadiazole, benzooxadiazole, and related core structures for use in small molecule solar cells and transistors, which exhibit broad optical absorption, deep HOMO levels, and planar structures, allowing for efficient charge carrier mobility and solution processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polymer based bulk heterojunction devices are used, then ease of processing and solution processability are improved, but batch-to-batch variations and structural definition are worsened
Solution Approach 1:
The patent uses small molecule compounds as discrete, well-defined structural copies that eliminate the polydispersity inherent in polymers. Each small molecule has a precise molecular weight and structure, enabling reproducible batch-to-batch performance while maintaining solution processability through molecular design with appropriate solubilizing groups.
Solution Approach 2:
The patent changes the fundamental parameter from polymeric chains to discrete small molecules, transitioning from a distribution of molecular weights to a single defined molecular weight. This parameter change eliminates batch-to-batch variations while preserving solution processability through careful selection of molecular structure and solubilizing side chains.
2Manufacturing precision
If small molecule bulk heterojunction devices are used, then structural definition and mono-dispersity are improved, but attention and development resources are worsened
Solution Approach 1:
The patent segments the molecular structure into distinct functional units: light-harvesting chromophores, charge transfer bridges, and electron-accepting units. This segmentation allows independent optimization of each component and facilitates systematic structure-property relationship studies, accelerating development while maintaining precise structural definition.
Solution Approach 2:
The patent develops a universal platform of small molecule donors with standardized core structures (e.g., dithienosilole, benzodithiophene) that can be systematically modified with different side chains and terminal groups. This universal platform approach enables rapid generation of molecular libraries while maintaining well-defined structures, addressing both precision and productivity needs.
3Use of energy by moving object
If broad optical absorption extending into near-IR is achieved, then photon absorption efficiency is improved, but molecular structure complexity is worsened
Solution Approach 1:
The patent creates composite molecular structures by combining electron-donating chromophores with electron-accepting units through conjugated bridges. This molecular composite approach extends optical absorption into the near-IR region through intramolecular charge transfer transitions while maintaining relatively simple modular structures that can be systematically designed and synthesized.
4Use of energy by moving object
If deep HOMO levels from -5 to -5.5 eV are achieved, then open circuit voltage is improved, but charge carrier mobility may be worsened
Solution Approach 1:
The patent applies local quality by introducing electron-withdrawing groups (e.g., fluorine, cyano, or carbonyl substituents) at specific positions on the molecular core to lower HOMO levels and increase open circuit voltage. These localized modifications achieve the desired energy level tuning without significantly disrupting the overall planar structure and π-π stacking necessary for charge carrier mobility.
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
These compounds demonstrate enhanced optical properties, facilitating efficient photon absorption and charge transport, leading to improved power conversion efficiencies in organic solar cells and transistors, with the potential for scalable and cost-effective production of molecular libraries.
Implementation Method 1
broad and efficient optical absorption that extends into the near-IR region to maximize photon absorption
Data Source
AI summary
Small organic molecule semi-conducting chromophores containing a halogen-substituted core structure are disclosed. Such compounds can be used in organic heterojunction devices, such as organic small molecule solar cells and transistors.