Equipment
We manufacture our solar cells in the clean room of the Ångström Laboratory. Here you can find information about the equipment we use to produce our solar cells.
How are solar cells made?
The division of solar cell technology (SCT) uses a wide range of systems for deposition and analysis of thin film solar cells and materials.
Two key manufacturing techniques for our thin film solar cells are co-evaporation and sputtering. They are also leading technologies for the industrial production of high-efficiency CIGS solar cells and therefore have the advantage that they can also be used in large-scale production.
Here you can read more about the equipment we use to manufacture solar cells.
Deposition
Most of the deposition tools are managed by SCT and situated within a university shared cleanroom, MyFab Uppsala. These tools have all the processes needed to make complete chalcogenide thin film solar cells.
Solar cell absorber
(Ag, Cu)(In, Ga)Se2
Co-evaporator using a masspectrometer feedback to control the power of the sources. Alkali post deposition treatments are also possible to do within the same system using a quartz crystal monitoring (QCM) readout.
Chalcogenide perovskites and Cu2ZnSnS4
Co-sputter with six target positions and with the possibility of both pulsed direct current (DC) and radio frequency (RF) sputtering, where the deposition rates can be observed by QCM.
Post sulfurization and selenization
Possible to do in an external furnace and sulfurization can also be performed in a small rapid thermal anneal furnace mounted on the co-sputter mentioned above, allowing for sample transfer between the two without air exposure.
NaF precursor
Evaporator using QCM for film thickness control.
Contacting layers
Buffer layer or transparent electron transport layer (ETL)
CdS, ternary ZnO compounds and ternary SnOx compounds are possible to deposit using atomic layer deposition (ALD) and heated chemical bath deposition (CBD). There is an option to do in-situ monitoring of the ALD process using either QCM or ellipsometry.
Transparent conducting oxide (TCO)
A sputter with the possibility of both DC and RF hosts several options for TCO depositions including Indium tin oxide (ITO) and ZnO:Al. This system belongs to the shared cleanroom facility MyFab Uppsala
Metals
Various metals including Mo, Al, and Ni are available through electron beam (e-beam) evaporation and sputtering. During evaporation it is possible to mount shadow masks for metal grid deposition. A wider variety of metals are available in the sputter and evaporation tools belonging to the shared cleanroom facility MyFab Uppsala
Miscellaneous
Anti reflection coating
MgF2 evaporator using QCM for film thickness control.
Cell area definition
Scriber tool using either a needle to mechanically remove layers or a green laser that ablates the layers away. Another option is to use the fully fledged lithography bay belonging to the shared cleanroom facility MyFab Uppsala in combination with chemical etching of the TCO to define the cell area.
Glass substrate cleaning
Automated washer accompanied by a spin rinse dryer.
Analysis
Analysis tools are used to gain knowledge about everything from the complete solar cells to the local arrangements of atoms within specific materials. Most of the tools on the list below belongs to SCT, but there is also a set of tools that are hosted elsewhere within the Ångström laboratory that are frequently used by SCT.
Electrical and optical
Current density versus voltage (JV)
One system using a halogen lamp and one setup using an ABA solar simulator. Both systems have adjustable light intensity and a temperature-controlled stage.
External quantum efficiency (EQE)
Two systems that also offer possibilities to use biasing with light and electrical potential.
Current, capacitance, voltage and temperature (ICVT)
A system using a controllable light source in an otherwise dark chamber, an admittance reader and a Peltier controlled temperature stage.
Optical transmittance and reflectance
A system using wavelengths spanning from UV to IR, monochromator and an integrating sphere. The integrating sphere can be modified to get rid of the specular component of the reflectance.
Photoluminescence (PL)
Measures steady state in both excitation and emission mode. The system also allows for electroluminescence if an external voltage source is used. This system belongs to the shared cleanroom MyFab Uppsala
Chemical and structural
X-ray fluorescence (XRF)
A system using a set of secondary targets to get good signal to noise ratio for most elements.
Glow discharge optical emission spectroscopy (GDOES)
A system with a very high element sensitivity, down to doping levels. The system gives depth profiles as the technique analyzes atoms that are continuously removed from the film.
X-ray photoelectron spectroscopy (XPS)
The system uses Al Kα radiation and has possibility to ion mill the samples to create depth profiles. This system belongs to the shared cleanroom MyFab Uppsala.
Electron microscopy
The shared cleanroom MyFab Uppsalah osts a wide variety of electron microscopes for analysis of micro- and nanoscale structures and their chemistries. SCT are e.g. frequent users of scanning tunneling electron microscopy (STEM) – energy dispersive X-ray spectroscopy (EDS) and electron beam induced current (EBIC), which provide very local information on the chemical and electrical properties within a material respectively. There is also an option to structure or slice materials up using the electron microscope equipped with a focused ion beam (FIB).
X-ray diffraction (XRD)
A wide variety of setups for both film and powder analysis exists within the shared X-ray lab hosted by the Department of Chemistry Ångström
Raman spectroscopy
The system belongs to Department of Chemistry Ångström [https://www.kemi.uu.se/angstrom/?languageId=1] and has a selection of light sources with different wavelengths.