Perovskite Solar Cell Processing

The first solar panels were based on silicon wafers, and c-Si, or crystalline silicon, continues to be the dominant material used in photovoltaics. But ever since the first solar panels were deployed, there has been a continuous quest for higher efficiency and lower cost panels. A second-generation material, CdTe, or cadmium telluride, is a thin-film semiconductor that has begun to achieve commercial success. Although not as efficient as silicon, CdTe is lower cost.

A third-generation material, Perovskite, could be a game-changer. It has the potential for both higher efficiency and lower cost compared to c-Si and CdTe. However, Perovskite is still laboratory-based and has not yet reached commercial viability. Nevertheless, the growth rate of Perovskite's demonstrated efficiency has been faster than that of silicon and CdTe.

Lasers Will Help Enable Commercial Viability of Perovskite Solar Cells

Perovskite solar cell manufacturing is a roll-to-roll process. Part of the process involves removing very narrow portions of thin-film layers of material in a multi-film stack without delamination or debris. This is commonly referred to as "patterning" or "scribing," which is done to achieve monolithic serial interconnections with adjacent cells. Traditional mechanical scribing methods, such as with a blade, and wet chemical etching methods have limitations and may cause undesired problems. Thankfully, a superior solution for Perovskite solar cell manufacturing is available: lasers. Here are some of the reasons why.

Lasers are very high precision devices that can perform accurately and repeatability on the order of microns. This helps increase manufacturing yields. By contrast, traditional mechanical tools cannot reliably perform on nearly the same scale. In addition to their high precision, lasers offer more variable and intricate patterns for scribing compared to mechanical tools, which may enable more complex, and possibly more efficient, Perovskite solar cell designs.
Lasers deliver higher quality results by producing fewer burrs than mechanical scribes and cuts do with less thermal damage to the surrounding areas. This further results in higher manufacturing yields, as less of the material is wasted. Additionally, this can also lead to better quality and reliability of the product in the field, as fewer of these issues will end up in the final assembly.
Laser scribing is a contact-free operation with no tool wear. Thus, replacement downtime is exceedingly infrequent by comparison to mechanical methods.
Lasers are a more "green" technology. By contrast, a particular concern of wet chemical etching is that the waste management required presents extra complications and costs. Lasers, however, do not produce environmental waste.

Taken all together, MKS believes that incorporating lasers into Perovskite solar cell manufacturing will help to accelerate their commercial viability.

Figure 1. Schematic of laser-based Perovskite cell patterning and selective layer material removal to construct finished cell and achieve monolithic serial interconnection with adjacent cells.

MKS Solutions for Perovskite Solar Cell Processing

Challenges in Perovskite Processing	MKS Solutions
Selective removal of targeted materials without delamination	High-power UV, green and IR lasers to ablate required materials High power/high fluence optics to manage the lasers
Precise, repeatable control of manufacturing process	Lasers with versatile and consistent pulse control Power meters and beam profilers to ensure optimal laser output Robust, stable optical mounts
Preventing collateral damage, contamination or particle generation	Ultrafast lasers for highest quality micromachining
Scaling capacity at larger surface areas	High-power lasers for more operations

Your Partner for Perovskite Solar Cell Processing

50+ years and thousands of laser micromachining systems for industrial applications
Long-term partner to photovoltaic processing companies
Full range of products: lasers, optics, opto-mechanics, beam analysis
- Custom capabilities
- Product availability
Ability to scale with you

Global corporation and presence

Lasers	Beam Analysis	Optics	Opto-Mechanics
Ultrafast (femtosecond and picosecond) and nanosecond lasers DPSS Q-switched lasers UV, green and IR lasers	Laser thermal sensors Beam profilers Laser power/energy meters	High energy mirrors High energy lenses High energy beamsplitters Zero order waveplates UV, visible and IR optics	Mirror mounts Lens positioners Prism mounts Posts and pedestals Manual positioners

Lasers

Criteria for Selecting Lasers

When choosing a laser, there are several criteria to consider. First is the application or function of the laser – for Perovskite solar cell manufacturing, it is patterning by ablation, and more specifically, sequential removal of thin film by ablation. Next, the requirements of the application must be addressed, including the type and thickness of the material to be processed. For Perovskite solar cells, this includes not only Perovskite but also hole-transport, electron-transport, top electrode, back contact and glass coating materials whose thicknesses will be on the order of microns. Then, the specifications of lasers, such as wavelength and power, must be evaluated. Listed here are the criteria that MKS believes are most important when selecting lasers for Perovskite solar cell processing.

Application Requirements
- Function
- Type of Material & Thickness
- Speed
- Resulting Size of Heat Affected Zone (HAZ)
Laser Specifications
- Wavelength
- Power
- Pulse Width and Repetition Rate
- Stability

Perovskite Solar Cell Processing Lasers

IceFyre® Picosecond Lasers: Versatile UV, green and IR picosecond lasers: The new standard for picosecond micromachining.

	IceFyre^®
Wavelengths	UV	Green	IR
Power	Up to >50 W
Pulse Width	<12 ps	<15 ps
Repetition Rates	Single Shot to 10 MHz
Max Pulse Energy	Up to >60 µJ	Up to >100 µJ	Up to >200 µJ
Power Stability	<1%, 1 σ, over 8 hours
Other Features	24/7 industrial reliability TimeShift™ technology for pulse control Laser/controller in single, compact package

IceFyre ^®FS Femtosecond Lasers: Highest performing fs lasers on the market for 24/7 micromachining of critical materials

	IceFyre^® FS
Wavelengths	UV	IR
Power	>50 W @ 1 & 1.25 MHz	>200 W @ 1-50 MHz
Pulse Width	<500 fs
Repetition Rates	Single Shot to 3 MHz	Single Shot to 50 MHz
Max Pulse Energy	>50 µJ @ 1 MHz	>200 µJ @ 1 MHz
Power Stability	<1% rms over 8 hours (after warm-up)
Pulse-to-Pulse Energy Stability	<2% rms
Other Features	24/7 industrial reliability TimeShift™ technology for pulse control Laser/controller in single, compact package

Talon^® Ace™ High-Power UV Laser with Programmable Pulses: Highest single-mode ns UV power in the industry, with TimeShift™ programmable pulse capability

	Talon^® Ace™
Wavelengths	UV
Power	>100 W
Pulse Width	<2 or 50 ns
Pulse Energy	>500 µJ
Repetition Rates	Single shot to 5 MHz
Pulse-to-Pulse Energy Stability	<3%, 1 σ
Other Features	24/7 industrial reliability TimeShift technology for pulse control Laser/controller in single, compact package

Talon^® Diode-Pumped Solid State Q-Switched Lasers: Superior combination of performance, reliability and cost

	Talon^®
Wavelengths	UV	Green
Power	>45 W	>70 W
Pulse Width	<25 or 35 ns	<25 or 43 ns
Pulse Energy	Up to 500 µJ	Up to 1000 µJ
Repetition Rates	0 to 500 kHz	0 to 700 kHz
Pulse-to-Pulse Energy Stability	<5% rms
Other Features	24/7 industrial reliability E-Pulse™ technology for superb stability Laser/controller in single, compact package

Explorer One: The most compact UV and green nanosecond lasers in its class with high peak power and short pulse widths.

	Explorer One	Explorer One XP	Explorer One HP
Wavelength	UV, Green		UV
Power	Up to 2 W	2 W (UV) or 5 W (green)	>4 or >6 W
Pulse Width	<5, <10 or <15 ns	<10 ns (UV) or <12 ns (Green)	<12 or <15 ns
Repetition Rates	Single shot to 200 kHz	Single shot to 500 kHz	Single shot to 200 or 500kHz
M²	<1.3, TEM₀₀
Stability	<2%
Other Features	It’s in the Box™ design Very compact, lightweight air-cooled designs Thousands of hours in the field

Lasers for PV Perovskite Processing Selection Guide

Presented here is a summary of recommended MKS lasers for various Perovskite manufacturing applications. Please use this as a reference guide only, and always contact us to discuss your application and requirements in detail so that we may provide the best solution for you.

	IceFyre^®			IceFyre^® FS		Talon^® Ace	Talon^®	Explorer^® One
Material	UV (ps)	Green (ps)	IR (ps)	UV (fs)	IR (fs)
Perovskite	✓	✓		✓		✓	✓	✓
Hole-transport materials (e.g., Sprio-MeOTAD, NiOx)	✓	✓		✓		✓	✓	✓
Electron-transport materials (e.g., TiO₂, ZnO)	✓	✓		✓		✓	✓	✓
Top electrode / back contact materials (e.g., Ag, Pt, Au)	✓	✓		✓		✓	✓	✓
Coatings from glass surface (e.g., ITO, FTO)			✓		✓

Laser Beam Analysis

Even with the advantages that lasers provide over traditional tools, lasers systems can degrade over time, leading to reduced output power or a change in focus. This, in turn, could result in lower quality laser operations. Therefore, it is very important to monitor your laser beam frequently, and the critical parameters of the laser should be checked before and after each important step of the laser manufacturing process.

Figure 1. As the laser emerges from the laser source (left), it runs through a variety of laser delivery components, such as free-space optics and process fibers, which can change the power levels and beam profile (center). The laser beam next moves through the laser processing head. Mirrors and lenses and cover glass can also have a significant impact on power levels, size, and shape (right).

Laser Power Sensors

MKS offers a comprehensive portfolio of power sensors. Shown here are examples of sensors designed to measure optical output power of short-pulsed lasers, such as IceFyre, Talon and Explorer One that operate in fs, ps and ns pulse widths.

Laser Thermal Power Thermal Sensors: very high damage thresholds for hundreds of watts power measurement.

	F150(200)A-CM-16	30(150)A-SV-17	F80(120)A-CM-17
Spectral Range	0.248-9.4 µm	0.19-11 µm	0.248-9.4 µm
Power Range	300 mW - 200 W	100 mW - 150 W	100 mW - 120 W
Energy Range	50 mJ – 200 J	50 mJ – 300 J	50 mJ – 200 J
Max Avg Power Density	35 kW/cm²	60 kW/cm²	35 kW/cm²
Max Energy Density (2 msec)	45 J/cm²	50 J/cm²	45 J/cm²
Aperture	Ø16 mm	Ø17 mm	Ø17.5 mm
Response Time	3 sec	1.7 sec	2 sec
Other Features	Not water-cooled

Power Meters

Ophir laser power and energy meters work on the smart plug principle. This means that almost any power meter can work – plug and play – with almost any of the wide range of Ophir optical sensors.

Power Meters		Virtual Power Meters
Centauri	StarBright Handheld	Juno+	EA-1
Extensive graphic displays on 7-in full color touchscreen display Advanced measurement processing Single- or dual-channel versions USB and RS-232 interfaces, with user-friendly software application Analog and TTL output External trigger input	Portable use For transmission checks "in the field" Variety of measurement modes and displays USB & RS-232 interfaces	USB connection to use PC as monitor User-friendly software Extensive graphic displays of data Advanced measurement processing Data logging	Ethernet adapter enables remote control and monitoring of sensor Telnet, HTTP and UDP protocols supported Interact with sensor through custom software or MKS user-friendly software Data logging

Beam Profilers

SP932U Beam Profiling Camera: high resolution, real-time viewing and measuring of laser structure with highest accuracy in the industry.

	SP932U
Spectral Range	190-1100 nm
Damage Threshold	50 W/cm², 1 J/cm², <100 ns pulse width
Beam Sizes	34.5 µm to 5.3 mm
Pixels	2048 x 1536 Effective Pixels, 3.45 µm Pixel Size
PC Interface	USB 2.0
Other Features	BeamGage^® software included UltraCal™ correction algorithm Measures cross-sectional intensity 72 dB true dynamic resolution 24 Hz frame rate in 12-bit mode

Optics

Criteria for Selecting Optics

Wavelength
Laser Damage Threshold
- Substrate Material
- Coating
Reflectivity/Transmission
Size and Shape

High-Energy Laser Mirrors

High-energy laser mirrors optimized for 355, 532 and 1064 nm offer very high reflectivity and damage thresholds, and standard broadband metallic mirrors offer a more economic option for good performance and value over very broad spectral ranges.

	High-Energy Laser Mirrors
Wavelength	355 nm	532 nm	1064 nm
CW Damage Threshold	3 kW/cm²
Pulsed Damage Threshold	3.5 J/cm² @ 10 ns, 20 Hz	10 J/cm² @ 20 ns, 20 Hz	45 J/cm² @ 10 ns, 20 Hz
Reflectivity	R_s > 99.7% R_p > 99%
Diameter	1 and 2 inch
Substrate Material	UV Grade Fused Silica
Angle of Incidence	45°

High-Energy Plano-Convex Lenses

High-energy lenses optimized for 355, 532 and 1064 nm offer very high transmission and damage thresholds, and standard fused silica lenses offer good performance and value over very broad spectral ranges.

	High-Energy Spherical Lenses
Wavelength	355 nm	532 nm	1064 nm
Pulsed Damage Threshold	15 J/cm² @ 20 ns, 10 Hz
Average Reflectivity per Surface	< 0.25%
Diameter	1 inch
Substrate Material	High Purity Fused Silica

Nanotexture Surface Lenses

Highest laser damage resistance and lowest reflection loss

	Nanostructure Surface Fused Silica Plano-Convex Lenses
Wavelength	250 to 550 nm or 500 to 1100 nm
CW Damage Threshold	15 MW/cm²
Pulsed Damage Threshold	35 J/cm2 @ 10 ns, 1064 nm
Reflection Loss	0.1%
Diameter	0.5 in.
Shapes	Plano-Convex or Plano-Concave
Substrate Material	High Purity Fused Silica
Other Features	Sub-λ AR nanotextures etched directly into surface (no thin film coatings)

High-Energy Polarizing Cube Beamsplitters

Optimized for 355, 532 and 1064 nm, these cubes offer high damage thresholds, efficient polarization, and high extinction ratio.

	High-Energy UV Polarizing Cube Beamsplitters	Laser Line Polarizing Cube Beamsplitters
Wavelength	355 nm	532 nm	1064 nm
Pulsed Damage Threshold	5 J/cm²	10 J/cm²
Reflectivity	R_s > 99%	R_s > 99.5%
Transmission	T_p > 90%	T_p > 95%
Extinction Ratio	T_p/T_s >200:1
Size	1 in.	0.5 in.
Substrate Material	UV Grade Fused Silica
Other Features	Optically contacted, no cement

Zero-Order Waveplates (λ/4 and λ/2)

Very high damage threshold, low sensitivity to temperature and wavelength variation.

	Zero-Order Waveplates
Wavelength	355 nm	532 nm	1064 nm
CW Damage Threshold	2 MW/cm²
Reflectivity per Surface	< 0.25%
Diameter	0.5 and 1 in.
Substrate Material	Quartz
Temperature Coefficient	0.0001 λ/°C
Other Features	±λ/300 retardation accuracy

Opto-Mechanics

Criteria for Selecting Optical Mounts

Resolution/Sensitivity
Long Term Stability
Lockable
Size and Shape

Optical component mounts are needed to hold and adjust optics. Long term stability and low drift is crucial. Minimizing drift caused by vibrations or thermal drift over time will ensure laser alignment to the desired spot and also reduce any potential downtime due to misalignment and errors. Having a locking mechanism on these mounts can also prevent misalignment of the beam, especially during shipping and also if anything else happens during usage.

HVM industrial mounts are recommended for robust long term usage in compact space. The Suprema^® mirror mount is excellent for its stainless steel construction that gives better thermal performance than an aluminum mirror mount. Ultra-fine 254-TPI adjusters provide alignment sensitivity as low as 1.5 arc sec. For applications that are really concerned about the thermal changes that can be potentially caused by prolonged high powered laser usage, the ZeroDrift™ version will compensate for some thermal changes as well. For those mirror mounts that need to be set-and-forget for a long period of time, we recommend the MFM flexure mirror Mount. These are excellent for their small footprint so that machine size can be reduced.

Suprema® Stainless Steel Mirror Mounts: The industry's best thermal performance for long-term stability.
M-Series Aluminum Mirror Mounts: The new standard for affordable mounts.

	Suprema	M-Series
Optic Diameters	0.5, 1 and 2 in.	0.5, 1 and 2 in.
Resolution	50, 100, 127 and 254 TPI	100 TPI
Angular Range	±7°	±4°
Material	Stainless Steel	Aluminum
Drive Types	Knob Hex Key Exchangeable Actuators	Knob Hex Key
Lockable Versions	Yes	No
Other Versions	Clear-Edge Front- and Rear-Loading Right- and Left-Handed Low Wavefront Distortion ZeroDrift™	Clear-Edge Front- and Rear-Loading Right- and Left-Handed

HVM Top-Adjust Mirror Mounts: For use in compact spaces so your hands do not have to cross the beam path for adjustment.
MFM Flexure Mirror Mounts: Designed for "set and forget" applications.

	HVM-Series	MFM-Series
Optic Diameters	0.5, 1 and 2 in.	0.5, 0.75 and 1 in.
Resolution	80 and 100 TPI	80 and 100 TPI
Angular Range	±2.5°, ±3° and ±3.5°	±2.5°
Material	Anodized Aluminum, Stainless Steel	Stainless Steel
Drive Types	Hex Key	Hex Key
Lockable Versions	Yes	No
Other Features	Front- and Rear-Loading Versions	Shock Resistant Front- and Rear-Loading Versions Adhesive wells for permanent mounting

A-Line™ Fixed Position Lens Mounts: Fast, easy and economic mounting, aligning and focusing of optics.
Compact Lens Positioners: ideal solution for applications with limited table space.
LP Precision Multi-Axis Lens Positioners: Highest performing lens positioners.

	A-Line	Compact	LP-Series
Optic Diameters	0.5 to 3 in.	0.5, 1 and 2 in.	0.5, 1 and 2 in.
Resolution	-	100 TPI	100 TPI
Adjustments	Fixed	XY, XYZ, XYZθxθy	XY, XYZ, XYZθxθy
Material	Aluminum	Aluminum	Aluminum
Other Features	Self-aligning design Large clear aperture Compatible with A-Line alignment system	Adapters for other optics Lockable positions	Zero-freeplay XY mechanism True Gimbal adjustments Independent non-influencing locks Adapters for other optics

Ultima® Gimbaled Cube/Prism Mount: Precision alignment of beamsplitter cubes and prisms.
RSP High Performance Optic Rotation Mounts: Smooth, continuous 360° rotation of optics.

	UGP-1	RSP-Series
Optic Size	0.5 and 1 in. cube	1 and 2 in.
Resolution	100 TPI	4 arc min
Angular Range	±5°	360°
Material	Aluminum	Aluminum
Drive Types	Knob w/ Hex Hole	Coarse: knurled edge Fine: knob
Lockable	Yes	Yes
Other Features	True gimbal motion Adapters for other optics	Full ball bearing races Adapters for other optics

ULTRAlign™ Crossed-Roller Bearing Steel Linear Stages: Highest smoothness, precision and stability.
SDS Low Profile Ball Bearing Steel Linear Stages: Lowest profile positioner for moderate loads

	Ultralign	SDS Low-Profile
Travel Range	13 and 25 mm	10, 16 and 25.4 mm
Axes of Travel	X, Z, XY, XZ and XYZ	X, Z, XY and XYZ
Angular Deviation	<100 µrad	Pitch: <100 µrad Yaw: <150 µrad
Bearings	Crossed-Roller	Ball (Gothic Arch Bearing Ways)
Material	Stainless Steel	Stainless Steel
Drive Type	Adjustment Screw Micrometer Motorized Actuator	Side-Mounted Micrometer
Lockable	Yes	Yes
Other Features	Extra thick plates for more stability Low profile Right- and left-handed configurations	<20 mm height Non-influencing locking mechanism

Resources

Perovskite Brochure(7 MB, PDF)