Vapor Deposition: A Game-Changer for Perovskite Solar, Researchers Say

olar photovoltaics (PV) is a key player in the sustainable energy game, essential for tackling global climate change. Right now, silicon-based systems lead the PV market, but they're hitting their efficiency ceilings. This shift opens up exciting opportunities for next-gen materials like perovskites. Renowned for their most efficient solar power conversion and swift progress, this type of solar cell is poised to shake up the industry.

Perovskite solar cells have made impressive strides in efficiency, leaving traditional PV materials in the dust and staking their claim as the future of solar technology. Right now, they're on the brink of hitting the market, offering potential solar panel efficiencies higher than those of older models. But here's the big question: Which manufacturing method will push them ahead in the market race? That's where vapor-based deposition takes center stage. Fresh research conducted by 21 organizations from 10 different countries, led jointly by the National Renewable Energy Laboratory (NREL) in the U.S. and Germany's Karlsruhe Institute of Technology (KIT), claims that leveraging this technique can speed up the introduction of perovskite thin film processing into the commercial solar market.

The Rise of Perovskite PV

The hybrid perovskite solar panels are leading the pack in the race for the next generation of solar power. According to NREL, they're proving their worth with impressive efficiency rates. Single-layer perovskite-based cells are hitting up to 26%, while multi-layer ones are nearing 34%. These numbers outshine older technologies like organic photovoltaics (with efficiency up to 19.2%), cadmium telluride (up to 22.3%), copper indium gallium diselenide (up to 23.6%), and even the most common multi-crystalline silicon solar (up to 23.3%).

A perovskite PV cell is a special kind of solar cell made from a compound with a perovskite structure, usually a mix of organic and inorganic materials like lead or tin halides. This material's crystal arrangement is particularly effective at turning sunlight into electricity. Perovskite-based cells have sparked excitement because they could offer impressive power conversion rates, affordable production, and simple manufacturing techniques. But, like with any new technology, there are still some things to figure out, like making sure these cells can last a long time and hold up in all sorts of weather.

Unpacking the Deposition Techniques

Thin-film solar cells, such as those made from perovskite, are crafted by applying one or more thin layers of photovoltaic material onto a surface like glass, plastic, or metal. This step is called deposition, and it’s a key part of the manufacturing process. The way these layers are deposited plays a massive role in the solar cell’s performance, efficiency, and overall value for money. Solar production uses a mix of different deposition methods, each with its own pros and cons, tailored to specific needs. The research we're examining focuses on solution-based or vapor-based deposition methods.

Solution-Based Approaches: The Current Leader

Right now, solution-based approaches are at the forefront of the industry. These methods use inks made from materials that are dissolved in liquids. The inks are then applied to surfaces using various techniques such as spin-coating, blade-coating, and spray-coating. Valued for their simplicity and versatility in laboratory settings, solution-based methods are particularly attractive for their potential in efficient, cost-effective roll-to-roll production, which is similar to how newspapers are printed or walls are painted. While these techniques have been highly effective in the lab, scaling them up for larger industrial use remains a significant hurdle.

Vapor-Based Approaches: Gaining Ground

In contrast, vapor-based deposition, a technique that has been pivotal in the commercialization of other thin-film technologies such as OLEDs, involves converting precursor materials into a vapor under vacuum conditions, which then condenses onto a substrate to form highly uniform films. This method's uniqueness lies in its minimal process variables, which allow for easier scaling up and quality control during manufacturing. In the past, vapor-based methods played a crucial role in creating widespread markets for various PV technologies, providing a dependable way to produce them in large quantities.

In their research, scientists point out that vapor-based techniques, despite being less common, are proving effective in large-scale uses of perovskite solar modules. Given the solar industry's successful shift to vapor-based processes for other highest efficiency solar cells, there seems to be a viable route for scaling up perovskite production as well.

Why Vapor-based Deposition Stands Out

The team has highlighted several key advantages of using vapor-based deposition for producing perovskite solar cells, particularly as this technology progresses towards commercial use. Here’s a breakdown:

• Uniform Film Quality: Vapor deposition creates very consistent and smooth layers. This uniformity is a big deal for large-scale production where any small defect can reduce the PV panel efficiency. The process ensures that the perovskite films are even and free from defects such as pinholes or leftover solvents, which are often seen in modules made by solution processes.

• Improved Device Performance: Solar cells made with vapor-based methods generally perform better. For example, they often have a higher fill factor, which means they're losing less energy through things like shunt and series resistances. This improvement comes from the even layers and consistent coverage created through vapor deposition.

• Simpler Process Control: Compared to solution-based methods, vapor deposition is less complex. It involves fewer variables, making it easier to monitor, control, and replicate. Keeping it simple is essential when you're looking to increase production for industrial needs. It results in more uniform products and increased production yields.

• High Throughput Potential: While vapor-based methods are on the slower side right now, there's a lot of room to increase the speed of production. Innovations in how the material is deposited, like dynamic co-evaporation and using several sources at once, could greatly accelerate the process. Speeding up is crucial for vapor deposition to hold its own against other fast-paced manufacturing techniques like roll-to-roll printing seen in thin-film tech.

• Flexible Material Choices: Vapor deposition allows for the use of a wide range of materials, including hybrid organic-inorganic perovskites. This lets manufacturers tweak the solar cell’s characteristics to create the best efficiency solar panels.

• Top-Quality Interfaces: Vapor deposition can create high-quality interfaces between the different layers of the solar cell, crucial for minimizing energy losses. Techniques like interface passivation, which boost the efficiency and longevity of the cells, are easier to integrate into vapor-based processes.

Industrial and Research Dynamics

The paper also delivers a first-of-its-kind examination of the industrial landscape for perovskite products, surveying 89 companies globally. These include module manufacturers, equipment suppliers, and material providers. This extensive overview sheds light on the industrial dynamics surrounding perovskite photovoltaics.

In their analysis, the research team found that although solution processing is prevalent in the literature, there's a noticeable shift in practices among commercial manufacturers. They discovered that among the world’s top 15 solar module manufacturers, which encompass both silicon and cadmium telluride (CdTe) PV manufacturers, seven are exploring perovskite PV. Of these, six are adopting vapor phase processing exclusively or in combination with solution processing.

The study revealed that 40% of module manufacturers and a striking 70% of equipment manufacturers are exploring vapor phase deposition or a mix of vapor and solution approaches. Notably, while large companies are interested, it's the small startups that are taking the lead in using solution processing to manufacture perovskite solar panels and related equipment.

Looking Ahead

We're on the brink of something big in the quest to make perovskite solar panels most efficient and seamlessly incorporated into our lives. Vapor-based deposition holds a lot of promise, but there are hurdles to overcome. Scientists need to figure out how to make it faster, more stable, and easier to use alongside other technologies. If they get it right, vapor-based methods could be the ticket to unleashing the full potential of perovskites. With these technologies expected to hit the market around 2025, the next few years are crucial for turning possibilities into practical solutions.

Sources:

https://www.nrel.gov/pv/cell-efficiency.html

https://pubs.rsc.org/en/content/articlelanding/2024/ee/d3ee03273f