Perovskite solar cells (PSCs) have shaken up the renewable energy scene. They’ve soared past 25% efficiency, hinting at a future where solar power could be both affordable and high-performing.
But scaling up production? That’s the real sticking point. It mostly comes down to how we deposit the functional layers inside these devices.
A recent study put two popular techniques head-to-head: spin coating and doctor blade coating. The researchers used both methods to apply copper sulfide (CuS) thin films as hole transport layers (HTLs).
The results? There are notable trade-offs between precision and scalability. These findings could help guide large-scale manufacturing without totally giving up on performance.
Spin Coating vs. Doctor Blade Coating in PSCs
Spin coating is a lab favorite. It makes highly uniform films with excellent crystallinity, which is crucial for PSC prototypes.
Still, it wastes a lot of material, doesn’t handle big surfaces well, and isn’t practical for industrial-scale production. Doctor blade coating, on the flip side, is gaining ground as a cost-effective, scalable alternative.
It cuts down on material waste, works with flexible substrates, and supports large-area production. That makes it a strong candidate for commercial applications—at least in theory.
Copper Sulfide as a Hole Transport Layer
CuS stands out as an HTL material because of its stability, p-type conductivity, and excellent energy alignment with perovskites.
People have dug into CuS properties before, but not much has been done to compare how different deposition techniques affect its performance in PSCs. This study tried to fill that gap and offer some practical insights.
Structural and Optical Properties of CuS Films
Structural analysis turned up some clear differences between the two methods:
- Spin-coated films had smaller crystallites, less strain, and fewer defects.
- Doctor blade films produced larger grains but came with more defects.
Both types of CuS films stayed transparent in the visible spectrum. That’s crucial for letting as much light as possible reach the perovskite absorber layer.
The bandgap values were 3.23 eV for spin-coated films and 3.15 eV for doctor blade films. Both allow efficient light transmission.
Energy-Level Alignment and Hole Extraction
Doctor blade coating showed improved energy-level alignment with the well-known perovskite MAPbBr₃. This helps boost hole extraction efficiency, which is a big deal for device performance.
Spin coating gives you fewer defects, but the unique energy compatibility of doctor blade films could help balance out some of those structural issues—at least in practical applications.
Comprehensive Characterization Techniques
The team used a bunch of scientific tools: X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), UV-Vis spectroscopy, X-Ray Photoelectron Spectroscopy (XPS), and Ultraviolet Photoelectron Spectroscopy (UPS).
They also ran drift-diffusion simulations to model and compare the electrical behavior of PSCs with each type of HTL. This mixed approach meant their findings had both solid data and theoretical support.
Industrial Implications
When you think about mass production, doctor blade coating really starts to shine:
- It uses less material, which means lower costs and less environmental impact.
- It’s easier to fit into roll-to-roll manufacturing systems.
- It works with flexible substrates—great for lightweight, portable solar panels.
Those perks make it a compelling option, even if the films have a few more defects.
Conclusion: A Sustainable Route Ahead
Spin coating and doctor blade coating both make solid copper sulfide HTLs for high-performing PSCs. Still, doctor blade coating feels like the more promising choice for scaling up production.
It keeps optical transparency intact and lines up well with energy levels, even if it comes with a few more defects. Manufacturers can lean into scalability here without losing too much on the performance front.
Spin coating probably stays the favorite for research labs chasing precision. But if a company wants to launch PSC technology on a bigger scale, doctor blade coating strikes a practical balance between quality and mass production.
Here is the source article for this story: Influence of deposition technique on the structural and optical properties of CuS thin films for hole transport layers