Dithieno Copolymer Solution Stability for Organic Solar Cells

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Solution Overview

Problem

Organic semiconductor materials used in electronic devices tend to gel when left standing in solution, making it difficult to form stable films for applications like solar cells.

Innovation Solution

A copolymer with specific repeating units, including a dioxopyrrole condensed ring and a dithieno condensed ring, is developed to maintain stability in solution and enhance light absorption at longer wavelengths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If copolymer with dioxopyrrole and dithieno condensed rings is used to absorb long wavelength light, then light absorption efficiency is improved, but solution stability deteriorates causing gelling

Engineering Contradiction:

Improvelight absorption efficiencyVSAvoidsolution stability

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The patent modifies the chemical structure parameters of the copolymer by introducing specific substituent groups (alkyl, alkoxy, aryl, or heteroaryl groups) at defined positions on the dithieno condensed ring. This structural parameter change reduces intermolecular interactions that cause gelling while preserving the extended pi-conjugation needed for long-wavelength light absorption, thereby improving solution stability without sacrificing optical performance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite molecular structure combining dioxopyrrole condensed ring (electron-deficient) with dithieno condensed ring (electron-rich) units in alternating sequence. This donor-acceptor composite structure enables intramolecular charge transfer that extends absorption to longer wavelengths while the specific substituent pattern prevents intermolecular aggregation, resolving the contradiction between absorption efficiency and solution stability

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If copolymer is dissolved in organic solvent for film formation, then ease of manufacture is improved, but solution gels after standing causing manufacturing difficulty

Engineering Contradiction:

Improveease of film formationVSAvoidsolution stability during storage

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent introduces solubilizing substituent groups (particularly alkyl and alkoxy groups) at specific positions on the dithieno condensed ring, which increase the polymer's solubility and prevent intermolecular stacking that leads to gelling. This parameter change maintains the polymer's ability to form stable solutions during storage while enabling reliable solution processing for film fabrication

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The substituent groups act as intermediary elements that mediate between the polymer chains, preventing direct pi-pi interactions that cause gelling while maintaining solubility in organic solvents. These intermediary groups allow the polymer to remain in solution form during storage and handling, enabling ease of manufacture through solution processing

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS9249257B2Copolymer, organic semiconductor material, organic electrical device, photovoltaic module

Publication Date: 2016.02.02 MITSUBISHI CHEM CORP

AI summary

A copolymer containing a repeating unit having a dioxopyrrole condensed ring skeleton and a repeating unit having a dithieno condensed ring skeleton and also having a specific substituent is provided.