Copolymer Structure for Organic Solar Cells With Lower Recombination Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing organic solar cells face challenges in achieving high efficiency and economic feasibility due to electron and hole recombination losses, requiring additional processes that increase manufacturing costs.
Innovation Solution
A copolymer with specific chemical structures (Chemical Formulas 1, 3, 4, and 5-1) is used in the organic solar cell, comprising units A, B, and C, which allows for a large molecular weight, enhancing charge mobility and stability, and includes branch-chained alkyl or alkoxy groups to prevent excimer formation and improve solubility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional processes are used to transport electrons or holes to electrode without loss, then charge transport efficiency is improved, but manufacturing cost increases
Solution Approach 1:
The copolymer is designed with built-in electron donor and acceptor units that enable self-transport of charges through the polymer backbone. The alternating donor-acceptor structure allows electrons and holes to move along the polymer chain without requiring additional transport layers or complex multi-step processes, thus achieving efficient charge transport while maintaining simple manufacturing
Solution Approach 2:
The copolymer combines electron donor units (thiophene derivatives) and electron acceptor units (pyrrolopyrrole-diketone derivatives) into a single integrated material. This composite structure at the molecular level enables both charge generation and charge transport functions within one material, eliminating the need for separate additional processes and reducing manufacturing complexity
2Reliability
If copolymer with large molecular weight is used, then charge mobility and thermal stability are improved, but synthesis complexity increases
Solution Approach 1:
The copolymer is synthesized by segmenting the synthesis into two clear stages: first preparing the electron donor monomer with bromine substituents, then performing coupling reaction with the electron acceptor monomer. This segmented approach to monomer preparation and polymerization simplifies the overall synthesis of high molecular weight copolymer by breaking down complex reactions into manageable steps with clear control points
Solution Approach 2:
The synthesis employs specific parameter control including using Pd(PPh3)4 catalyst at controlled temperatures, adjusting monomer ratios, and controlling reaction time to achieve high molecular weight copolymer. By optimizing these parameters, the synthesis complexity is managed while achieving the desired large molecular weight for improved charge mobility and thermal stability
3Ease of manufacture
If branch-chained alkyl or alkoxy groups are included in copolymer, then solubility is improved, but molecular weight may be reduced
Solution Approach 1:
Branch-chained alkyl or alkoxy groups are introduced locally at specific positions on the thiophene rings (positions 2 and 5) rather than throughout the entire polymer structure. This localized modification provides sufficient solubility enhancement for solution processing while minimizing the impact on the overall conjugation length and molecular weight of the copolymer backbone
Solution Approach 2:
The copolymer creates a composite structure combining the hydrophobic aromatic backbone with hydrophobic but bulky branch-chained alkyl/alkoxy side groups. This composite molecular architecture provides both the solubility needed for processing and maintains sufficient molecular weight by keeping the side groups as substituents rather than reducing the backbone chain length
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
The copolymer enables high-efficiency organic solar cells with improved open circuit voltage and thermal stability, reducing manufacturing time and costs while maintaining device efficiency, even without a tandem structure.
Implementation Method 1
An organic solar cell is a device that can directly convert solar energy into electric energy by applying a photoelectromotive effect
Implementation Method 2
One of the factors of the electric charge loss is extinction caused by recombination of the generated electrons and holes. Various methods have been proposed as a method for transporting the generated electrons or holes to an electrode without a loss
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present specification provides a copolymer and an organic solar cell including the same.