The Future of Flexible, Efficient Photovoltaics
Imagine a future where every surface—from your clothing to your car windows—could harness the power of the sun. This isn't science fiction; it's the promise of ternary nonfullerene polymer solar cells.
Explore the TechnologyUnlike traditional silicon panels that are rigid and heavy, organic solar cells are lightweight, flexible, and can be printed like newspaper using low-cost, energy-efficient processes. Recent breakthroughs have propelled their efficiency to impressive levels, with some laboratory devices now surpassing 19% efficiency—a figure once thought impossible for organic photovoltaics 5 .
At the heart of this revolution lies a clever design strategy: incorporating two polymer donors with an organic semiconductor acceptor to create ternary blends that capture more sunlight and convert it more effectively into electricity.
In this article, we'll explore how these sophisticated chemical concoctions are transforming solar energy and paving the way for a future powered by truly ubiquitous solar harvesting.
Can be integrated into various surfaces and materials
Recent devices achieving nearly 20% power conversion
Printable using energy-efficient processes
Organic solar cells (OSCs) represent a radical departure from conventional silicon-based photovoltaics. Instead of rigid silicon wafers, OSCs use carbon-based molecules or polymers to capture sunlight and generate electricity 5 .
Their molecular structures can be carefully designed and modified to achieve specific electronic properties, making them incredibly versatile.
The "ternary" in ternary solar cells refers to the use of three complementary components in the light-absorbing layer, typically two donors and one acceptor or one donor and two acceptors.
Analogy: If binary blends are a simple duet, ternary blends are a sophisticated trio where each singer brings a unique vocal range that complements the others.
This strategic combination allows scientists to fine-tune the properties of the active layer in ways that aren't possible with simpler binary systems 3 4 .
The advent of nonfullerene acceptors (NFAs) has fundamentally transformed the field. Unlike their fullerene predecessors, these materials can be systematically engineered at the molecular level to achieve desired properties.
The result has been a dramatic acceleration in efficiency gains—from just 6% in 2015 to over 20% today 6 .
Performance improvement with NFAsIn ternary systems, each component performs a specific function:
This approach enables more efficient light harvesting and charge generation compared to binary systems.
Ternary systems optimize all three processes simultaneously
The strategic combination of ternary architectures with nonfullerene acceptors has yielded remarkable performance improvements in recent years.
Researchers reported ternary nonfullerene polymer solar cells with 13.51% efficiency and a record-high fill factor of 78.13% .
Addition of PC₇₁BM as a second acceptor to a PBDB-T:IDT-EDOT system boosted performance from 9.93% to 12.07% 1 .
Rapid efficiency improvements in ternary organic solar cells over the past decade
| Year | System Composition | Reported Efficiency | Key Advancement |
|---|---|---|---|
| 2018 | PBDB-T:IT-M with polymer P1 | 13.52% | Record fill factor of 78.13% |
| 2020 | PBDB-T:IDT-EDOT:PC₇₁BM | 12.07% | Broad operating window, improved phase purity 1 |
| 2023 | PM6:PY-DT with PYF-T-o | 18.15% | High performance in all-polymer system 7 |
| 2025 | PM6:L8-BO:ZY-4Cl | 19.90% | Significant energy loss suppression 4 |
| 2025 | PBDB-T:QDT1:Y6 | 13.31% | Quinoidal acceptor with complementary absorption 3 |
One of the most significant advantages of well-designed ternary systems is their ability to reduce energy loss—particularly the nonradiative losses that have long plagued organic solar cells.
A 2025 study showed that incorporating a nonfullerene small molecule called ZY-4Cl into a PM6:L8-BO blend suppressed trap states and improved film morphology, leading to reduced charge recombination and an enhanced open-circuit voltage 4 .
Voltage loss comparison between different solar cell architectures
To understand how ternary solar cells work in practice, let's examine a pivotal study published in the Journal of Materials Chemistry A in 2020 that illustrates the ternary concept particularly well 1 .
The researchers started with a binary blend of the polymer donor PBDB-T and the nonfullerene acceptor IDT-EDOT, which itself achieved a respectable power conversion efficiency of 9.93%. They then introduced a third component—the fullerene derivative PC₇₁BM—in varying proportions to create ternary blends.
The experimental approach was systematic and thorough:
The researchers created multiple devices with different weight ratios of the three components, systematically varying the proportion of IDT-EDOT to PC₇₁BM while maintaining a constant donor concentration.
The findings revealed multiple advantages of the ternary approach:
The PC₇₁BM acceptor filled in absorption gaps in the binary system
PC₇₁BM helped disperse IDT-EDOT aggregates for better charge transport
Increased phase purity facilitates more efficient charge transport
Improved quantum efficiency indicating reduced nonradiative losses
| Parameter | PBDB-T:IDT-EDOT (Binary) | PBDB-T:IDT-EDOT:PC₇₁BM (Ternary) | Improvement |
|---|---|---|---|
| Power Conversion Efficiency | 9.93% | 12.07% | +21.6% |
| Open-Circuit Voltage (Vₒ꜀) | 0.85 V | 0.89 V | +4.7% |
| Short-Circuit Current (J꜀꜀) | 17.45 mA/cm² | 19.48 mA/cm² | +11.6% |
| Fill Factor | 66.94% | 69.58% | +3.9% |
What made this study particularly noteworthy was the discovery that the performance benefits persisted across a surprisingly wide range of acceptor ratios. Efficiency remained above 11% even as the IDT-EDOT to PC₇₁BM ratio gradually varied from 1:0.2 to 0.4:0.8 1 . This compositional flexibility is highly advantageous for manufacturing, as it suggests that precise ratio control may not be necessary, potentially lowering production costs.
The research provided crucial insights into how ternary systems can optimize multiple aspects of solar cell operation simultaneously—something that's exceptionally challenging with binary systems.
Creating high-performance ternary solar cells requires careful selection and combination of specialized materials. Each component serves specific functions in the complex dance of light absorption and charge generation.
| Material Category | Specific Examples | Function in Ternary Solar Cells |
|---|---|---|
| Polymer Donors | PBDB-T, PM6, PDPP-2S-Se | Contribute to light absorption, hole transport; form the matrix for charge generation 1 2 3 |
| Nonfullerene Acceptors | IDT-EDOT, Y6, ITIC derivatives, L8-BO, QDT1 | Primary electron acceptors; strongly influence absorption profile and energy level alignment 1 3 4 |
| Secondary Acceptors | PC₇₁BM, ZY-4Cl | Improve morphology, broaden absorption, enhance charge transport 1 4 |
| Solvents | Chlorobenzene, o-xylene | Process active layer materials; influence film morphology through drying dynamics 9 |
| Interface Layers | NiOx nanoparticles, PEDOT:PSS | Facilitate charge extraction at electrodes; improve device stability 9 |
The strategic combination of these materials enables researchers to create sophisticated multiphase systems where each component performs its specialized function while synergistically enhancing the overall system performance.
For instance, in the PM6:L8-BO:ZY-4Cl system that achieved 19.90% efficiency, the ZY-4Cl component served not only as a secondary acceptor but also as a morphology modulator that reduced trap states and improved charge extraction 4 .
When designing ternary solar cells, researchers consider several key factors for material selection:
The optimal combination depends on the specific system and desired properties, with energy level alignment being the most critical factor for efficient charge generation and collection.
Stability and lifetime remain significant concerns for organic solar cells. While recent ternary systems have shown improved operational stability compared to earlier generations, extending the lifetime to 10-15 years—as expected for conventional silicon panels—will require further material development and encapsulation strategies.
The NFA-15 project, a European research initiative, specifically targets this challenge with the goal of achieving 15% efficiency coupled with a 10-year lifetime 9 .
Scalability presents another major hurdle. The highest efficiencies are typically achieved in small-area devices (less than 1 cm²) fabricated using spin-coating in controlled inert atmospheres.
Translating these results to larger areas using printing techniques like doctor-blading or slot-die coating in ambient conditions has proven challenging. As one research group noted, there's typically a significant performance gap between small-area cells and larger modules 9 .
Ternary organic solar cells are currently at various stages of development, with fundamental research advancing rapidly while commercial applications are still emerging.
Windows, facades, and roofing materials that generate power while maintaining aesthetic appeal
Powering sensors, displays, and other low-power electronics in smart homes and offices
Integrating solar harvesting directly into clothing, backpacks, and accessories
Lightweight, flexible solar arrays for satellites and space missions
The potential of ternary systems is particularly evident under indoor lighting conditions. Remarkably, organic solar cells based on a PBDB-T:QDT1 active layer have demonstrated power conversion efficiencies greater than 23% under white LED illumination 3 —performance that rivals or exceeds traditional technologies in low-light environments.
Ternary nonfullerene polymer solar cells represent a fascinating convergence of molecular engineering, nanotechnology, and device physics.
By strategically combining two polymer donors with an organic semiconductor acceptor, researchers have created systems that are far more than the sum of their parts—they're sophisticated energy-harvesting platforms that can be fine-tuned to capture sunlight with remarkable efficiency.
The progress in recent years has been breathtaking, with efficiencies climbing from single digits to nearly 20% in just half a decade. While challenges remain in scaling up production and ensuring long-term operational stability, the potential of this technology is undeniable.
As research continues to refine our understanding of how multiple components interact at the nanoscale, and as new materials with tailored properties emerge, we move closer to a future where solar harvesting becomes truly ubiquitous—integrated seamlessly into our buildings, our devices, and even our clothing.
The journey of ternary solar cells illustrates how innovative thinking—asking "what if we add just one more component?"—can sometimes unlock dramatic advances. In the ongoing global effort to transition to renewable energy, such innovations will be crucial, and ternary organic solar cells are poised to play an important role in our solar-powered future.