Arecent article presented an overview of how lasers can play a key role in the development and production of solar devices, delivering twin benefits of lower fabrication costs and superior performance (see ILS, August , p. 24). Laser scribing is rapidly emerging as one of the most significant of all these processes as it is critically enabling high-volume production of next-generation thin-film devices, surpassing mechanical scribing methods in quality, speed, and reliability.
For more information, please visit our website.
These thin-film solar cells are important because they lend themselves to streamlined, high-volume manufacturing and greatly reduced silicon consumption. This results in dramatically lower fabrication costs per unit of power output compared to traditional silicon-wafer-based solar cells.
As implied by their name, “thin-film” devices typically consist of multiple thin layers of material deposited on sheet glass. While other formats and materials are at early stages of development, initial volume production of thin-film solar cells is being dominated by devices based on amorphous silicon (a-Si) in a so-called single-junction configuration (see Fig. 1). Multijunction a-Si variants such as the tandem ‘micromorph’ structure are expected to follow soon. But the laser-scribing processes described here are applicable to all other thin-film systems under development, including those based on CdTe (cadmium telluride) and cigs (copper indium gallium selenide).
FIGURE 2. After each of the different material thin films are deposited, the film must be patterned using narrow scribes to create a series of thin strip-shaped solar cells.Click here to enlarge imageEach panel starts off as a sheet of glass with a typical thickness of 3 mm. This is called a glass superstrate, because sunlight will enter through this support glass. The first step is to deposit a continuous, uniform layer of tco (transparent conductive oxide) with a typical thickness of a few hundred nanometers, which will form the front electrodes. This is followed by a scribe process called P1, which scribes through the entire layer thickness. The next step is vapor deposition of p- and n-type silicon with a total thickness of 2-3 µm, again followed by a scribing step, called P2, which completely cuts through the silicon layer. The final deposition is the thin (submicron) metal (Al or Mo) layer that forms the rear electrodes. These are patterned using a third scribe process, called P3. The panel is then sealed with a rear surface glass lamination.
To attain economic viability, thin-film devices must be produced in high volumes for low unit costs. Fast process throughput (short takt times) is critical to minimizing scribing costs. But high-quality scribes with very low defect counts are also necessary to deliver a high yield of final product with the highest possible electrical-conversion efficiency.
As with many other laser micromachining applications, both resolution and precision are important. Specifically, the area between P1 and P3 is a nonactive (that is, wasted or ‘dead’) area. Scribe lines are currently on the order of several tens of microns in width, with an offset separation between P1 and P3 of tens to hundreds of microns. But given that each cell has a total width of less than 10 mm, together with the importance of maximizing the inherently low conversion efficiency (6%-10% versus 15%-20% for bulk Si devices), it is vital to further minimize this already small scribe area. That means narrow scribes that are placed as close to each other as possible, with minimum offset. (Next-generation product is projected to use line widths in the 25-30-µm range.) The use of more closely spaced scribes requires very straight cuts that don’t wander out of alignment. Scribe narrowing also must be accomplished without increasing scribe defects.
Cut quality in terms of edge roughness and layer peeling is another important consideration, because solar conversion efficiency is substantially reduced by microcracks, and other types of surface and subsurface thermal damage. Therefore, it is vital to create scribes with a minimal haz (heat affect zone), smooth edges, and no recast debris.
However, this application is somewhat unique in that it must combine this precision, resolution, and edge quality with very high speed. Panels are produced in a continuous-flow production line. The typical amount of time a panel spends in a specific process step is widely considered to be in the range of only a few tens of seconds for small panels and a few minutes for larger sized panels. Yet each panel requires literally hundreds of meters of scribing. Even in workstations that utilize several lasers, scribe rates have to be in the range of 2 m/s, and each scribe has to be accomplished in a single pass. Moreover, active depth control is not realistic-each laser scribe depth must be naturally limited by material selectivity.
This does not represent a significant obstacle for the P1 scribe, which only needs to remove a few hundred nanometers of tco. Although quite demanding on certain laser parameters, it can be performed using conventional techniques with the near-infrared (1.06 µm) output of a Q‑switched dpss (diode-pumped solid-state) laser. But the P2 and P3 scribes must remove a few microns of thickness of silicon, plus the overlaying metal film in the case of P3. Conventional (thermal) materials processing cannot deliver the combination of single-pass speed, as well as cut quality and spatial resolution. Photoablation with a fast-pulsed UV laser is not an option, as this application would not sustain the cost of the laser and, more important, such a laser would provide no material selectivity and, hence, depth control: it would ablate all the materials and could damage the glass.
The solution is a laser lift-off process that has been developed in different forms for other applications. Instead of melting, vaporizing, or atomizing all the target material, this lift-off process vaporizes a small amount of material at the film interface, removing the overlaying layers entirely in a microexplosive effect. This is the principal reason that these scribes are performed through the glass (see Fig. 3). Specifically, P2 and P3 scribes are accomplished using a fast-pulsed green (532 nm) dpss laser.
Thin-film solar panels are an innovative alternative to conventional panels, offering a lightweight, bendy solution for people who want to generate clean energy whilst they’re on the go.
They’re also much cheaper than traditional solar panels, and are much quicker to install.
However, thin-film solar panels also come with a host of drawbacks, and certainly aren’t suitable for people looking to cut down their household energy bills.
To find out how much a traditional solar & battery system could save you on your energy bills, enter a few quick details below and we’ll provide an estimate.
Thin-film solar panels, also known as flexible solar panels or stick-on solar panels, are a type of photovoltaic (PV) panel used to generate electricity from sunlight. As their name suggests, they are extremely thin and lightweight, offering an alternative to heavier, rigid solar panels.
Microtreat are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together.
Although not as efficient as traditional crystalline panels (more on that later), they're cheaper canal boats.
The manufacturing process for thin-film solar panels is faster and wastes fewer raw materials than the production of crystalline silicon solar panels, which involves the energy-intensive preparation and slicing of silicon ingots.
In contrast, the manufacture of thin-film solar panels involves coating a base material (known as a substrate) with a thin layer of photovoltaic material, such as amorphous silicon (a-Si), cadmium telluride (CdTe), or copper indium gallium selenide (CIGS). The substrate is usually made from glass, metal or plastic.
Using laser scribing or etching, the manufacturer then cuts up the photovoltaic material into pieces to form individual solar cells and electrical pathways. Finally, a protective layer is added on top to protect the solar cells, ensuring they last longer and are shielded from environmental damage.
Thin-film solar panels work by capturing sunlight and converting it into electricity, just like any other PV panel.
The key difference lies in their thickness - thin-film solar panels are typically around 2-3 millimetres thick, whereas a traditional crystalline silicon solar panel is about 30-50 millimetres thick.
In fact, the latest thin-film solar panels made from kesterite can bend an astonishing 70 degrees, which sounds almost unnecessary.
A solar panel’s ‘efficiency’ refers to the percentage of sunlight hitting the panel that is being converted into electricity - so the higher the percentage, the better.
Compared to the typical 20-25% efficiency of monocrystalline solar panels, thin-film solar panels are around 7-13% efficient, which is significantly lower.
This means that you shouldn’t be getting thin-film solar panels to make a difference to your energy bills, as their output will never match up to what a traditional crystalline silicon solar panel system can produce. Instead, thin-film solar panels are only really suitable for people on the move.
Despite their advantages, thin-film solar panels are much less efficient compared to traditional crystalline silicon solar panels, so you'll need more of them to produce the same amount of electricity.
Flexible solar panels also have a much shorter lifespan and higher degradation rate over time, tending to last around 10-20 years before they need replacing. In contrast, monocrystalline silicon solar panels usually come with a 25-year or 30-year warranty, and can last upwards of 40 years.
Installing thin-film solar panels is usually a breeze - for most types, you can just peel off the protective backing and stick them wherever you please. But depending on the specific type of thin-film solar panel and its location, it may need drilling into place.
Regardless of the method, you'll need to connect the panels to an inverter to be able to actually use the electricity, so it's best to hire a professional installer to make sure it's a safe and efficient setup.
Are you interested in learning more about thin film solar module laser scribing system? Contact us today to secure an expert consultation!