Fullerene Derivative Blends for Stable, Cost-Effective OPV Acceptors
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Solution Overview
Problem
Organic photovoltaic devices (OPVs) based on liquid processed bulk heterojunctions face challenges in achieving high and stable power conversion efficiency (PCE) due to the instability of low-band-gap polymer-based devices, particularly under light soaking conditions, and the economic viability of using C70 derivatives as electron acceptors is limited by their higher cost compared to C60 derivatives.
Innovation Solution
The use of blends comprising two different types of fullerene derivatives, such as methanofullerenes and Diels-Alder adducts, in specific ratios, serves as electron acceptors in the active layer of OPVs, enhancing stability and maintaining initial PCE levels, while being more economically viable than using pure C70 derivatives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If C70 derivatives are used as electron acceptors to improve stability, then device stability is improved, but manufacturing cost increases
Solution Approach 1:
The patent uses composite fullerene blends combining C60 and C70 derivatives in specific ratios (e.g., 90:10, 80:20, 70:30) to achieve the stability benefits of C70 while reducing the overall cost by incorporating cheaper C60 derivatives. This composite approach allows optimization of both performance and manufacturing cost.
Solution Approach 2:
The patent systematically varies the composition ratio of C60 and C70 derivatives in the fullerene blend to optimize the balance between stability and cost. By adjusting parameters such as the proportion of C70 (5-40 wt%) and molecular weights of the derivatives, the patent achieves desired stability without requiring 100% C70 content, thereby reducing manufacturing cost.
2Productivity
If low-band-gap polymers are used to increase power conversion efficiency, then initial PCE is improved, but stability under light soaking deteriorates
Solution Approach 1:
The patent employs composite fullerene blends with specific C60:C70 ratios to complement the low-band-gap polymer donor materials. The combination of different fullerene types in the blend creates a more stable electron acceptor system that maintains high PCE while improving resistance to light-induced degradation.
Solution Approach 2:
The patent optimizes the local composition of the active layer by controlling the distribution and ratio of different fullerene derivatives within the blend. This local optimization ensures that the electron acceptance and charge transport functions are enhanced while providing localized stability against light soaking effects.
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 fullerene derivative blends demonstrate increased stability and thermal stability under annealing and light soaking conditions, with improved power conversion efficiency comparable to or exceeding that of devices using pure fullerenes, and offer a cost-effective alternative to C70-based solutions.
Implementation Method 1
efficient absorption of the solar light resulting in the efficient formation of excitons followed by charge transport to the electrodes
Implementation Method 2
the ratio of the first fullerene derivative to the second fullerene derivative is between about 97:3 and about 60:40
Data Source
AI summary
Fullerene derivative blends are described herein. The blends are useful in electronic applications such as, e.g., organic photovoltaic devices.