Tallinn University of Technology

Laboratory of Photovoltaic Materials

If solar energy is to become available to more people, smart material choices need to be made. The research group in the Photovoltaic Materials Laboratory is studying solar cells made from materials which are cheaper and more readily available than those used for today’s solar cells. 

Solar cells technology in our lab is based on unique monograin layer solar cell design. This technology is being implemented by Spin-off Company of TTÜ, crystalsol GmbH. The monograin layer technology (MGL) combines the high photoelectrical parameters of single crystals and advantages of polycrystalline materials and technologies: low cost and simple technology of materials and devices, the possibility to make flexible devices and to use the materials up to 100%. MGL technology allows to separate the materials formation from the module fabrication. Large area modules are fabricated at room temperature in a continuous roll-to-roll process. Homogeneous composition of powders gives an additional advantage and leads to homogeneous modules without any up-scaling problem. This technology can be used for different absorber materials. 

In addition to powder technology, several thin film technologies such as pulsed laser deposition (PLD), co-evaporation, electrodeposition and magnetron sputtering are applied for the growth of different thin film materials for photovoltaic applications. 

The laboratory also focuses on the studies of fundamental physical properties of semiconductors for optoelectronic applications such as solar cells, lasers, diodes, sensors etc. Our research infrastructure enables to explore the band structure, crystal and defect structure, phase and elemental composition, morphology, electrical and optical properties of the materials and devices.

Our current research is focused on the fundamental studies of different novel absorber materials for solar cells, for example Cu2ZnSn(S,Se)4, Cu2SnS3, Cu(In,Ga)Se2, SnS, CdTe, SnSe etc, and two-dimensional materials such as WS2, MoSe2 etc. The last mentioned have versatile applications in addition to photovoltaics, namely photonics, sensors etc. In addition to the inorganic semiconductor based structures, hybrid structures combining the advanatges of inorganic and organic semiconductors are being developed and studied. addition to the research, we are offer materials characterization service for all interest groups.

Contact: Marit Kauk-Kuusik

Päikeseenergeetika materjalide teaduslabori uurimisrühma liikmed


MARCH 2024

CUSTOM-ART project newsletter

December 2021

Tiny crystal of power as basis for solar cell (ESA)

June 2021

CUSTOM-ART project newsletter

April 2021

Custom-Art: making photovolatics more accessible to the everyday life of citizens.

Imagine if we could integrate a photovoltaic panel in any kind of building surface or in any kind of urban furniturewithout having any constraint regarding size, shape and weight.

This would open a new perspective for the distributed energy generation in urban areas, making "near-zero energy buildings and districts" a reality and improving citizen’s quality of life in a more sustainable environment.

However, mass adoption of Building Integrated Photovoltaics (BIPV) and Product Integrated Photovoltaics (PIPV) solutions can only be achieved by developing cost-efficient and sustainable thin-film technologies with unbeatable aesthetic functionalities, mechanical flexibility and optical tunability.

The European-funded Custom-Art project aims to develop next generation Building Integrated Photovoltaics and Product Integrated Photovoltaics modules based on earth abundant thin-film materials such as kesterites:

  • Custom-Art will bring flexible and semi-transparent kesterites solar modules to a higher level of maturity demonstrating very competitive conversion efficiencies and increased durability over 35 years at reduced production costs.

  • By combining advanced strategies for materials properties management with customized modules design, two types of products will be developed and demonstrated at real life operational conditions, including flexible and semi-transparent modules that will be integrated in building and urban furniture elements.

Custom-Art involves 17 partners and 3 Third Parties, including the world leading actors involved in the development of kesterite technologies.

Check up the new video release from Custom-Art in this link.

CUSTOM-ART is a H2020 funded project that stands for "Disruptive kesterites-based thin film technologies customised for challenging architectural and active urban furniture applications".

This project has received funding from the European Union’s H2020 research and innovation programme under grant agreement number 952982.




Maarja Grossberg and Jüri Krustok received the Estonian National Research award in the field of technical sciences. The scientists were recognized for their work with the optical spectroscopy of new 2D and 3D multiple semiconductors.

Maarja Grossberg explained: "We research the optical and electrical properties of new materials, mainly those aimed at solar energy applications. These properties determine the suitability and capability of the materials for those applications. Among these materials are environmentally friendly compound semiconductor materials and new-generation two-dimensional graphene-like materials with very special properties. The latter consist of only a few atomic layers."

Jüri Krustok added: "Our research has resulted in valuable information on the fundamental properties of new materials, helping to develop new technologies based on these materials."

The laureates' research focuses on the capability of environmentally friendly compound semiconductor materials to convert light energy into electricity using different methods of optical spectroscopy. The properties of semiconductor materials are largely determined by the defects contained in them. The laureates are committed to identifying them and researching the effects of these defects. Throughout their research, they have developed the traditional physics of compound semiconductor materials and proposed several new materials for future optoelectronics.

Professor Maarja Grossberg is the Head of the Laboratory of Optoelectronic Materials Physics at TalTech's Department of Material and Environmental Technology. Last year, she received a grant from the prestigious L’Oréal Baltic-UNESCO program "For Women in Science".

The topics of her research are the physics of semiconductors, the defect structure of semiconductor materials, and elements of the Sun. Grossberg is also a founding member of the Estonian Young Academy of Sciences, her doctoral thesis was supervised by Jüri Krustok.

Jüri Krustok is a professor of the Department of Cybernetics in the School of Science. He received a National Research Award in the field of technical sciences in 1998 as part of a collective: "Semiconductor materials for solar energy and optoelectronics". The topic of his research is the physics of semiconductors.

Grossberg and Krustok received the research award for the best research done and published in the last four years, i.e. 2017-2020, according to the statute of the National Research Awards.

October 2020

Custom-Art consortium leads an ambitious and disruptive EC funded project for the development and demonstration of the next generation of BIPV and PIPV modules based on abundant thin-film materials

Building- and product-integrated photovoltaics (BIPV and PIPV) are identified as key enabling technologies to make "near-zero energy buildings" and "net-zero energy districts" a reality. The mass adoption of BIPV and PIPV solutions can only be achieved by developing cost-efficient and sustainable thin-film technologies with unbeatable aesthetic functionalities, mechanical flexibility and optical tunability.

The EU-funded CUSTOM-ART project aims to develop the next generation of BIPV and PIPV modulesbased on abundant thin-film materials such as kesterites. The project will bring flexible and semi-transparent solar modules to a higher level of maturity (TRL 7), demonstrating very competitive conversion efficiencies (20 % at cell and 16 % at module levels) and increased durability (over 35 years), at a reduced production cost (less than EUR 75/m2).

By combining advanced strategies for materials properties management, with customized modules design in a circular economy approach, two types of products will be developed including flexible PV modules and semi-transparent PV devices. CUSTOM-ART will bring these technologies from TRL4-5 up to TRL7, demonstrating very competitive conversion efficiencies and durability (over 35 years), at a reduced production cost. They will exclusively use abundant elements and contributing to ensure the full sustainability and competitiveness of the European BIPV and PIPV Industry.

CUSTOM-ART is a H2020 funded project that stands for “Disruptive kesterites-based thin film technologies customised for challenging architectural and active urban furniture applications“. The kick-off meeting is held online from the 22nd to the 23rd of September, 2020.

The project has a total budget of 8M€ and will run for 42 months. It involves 17 partners across Europe that includes the world leading groups and main European actors involved in the development of kesterite technologies and Alejandro Pérez-Rodríguez  from IREC is the coordinator of the project.

More information: http://www.custom-art-h2020.eu/

This project has received funding from the European Union’s H2020 research and innovation programme under grant agreement number 952982.


December 2019

EurekAlert NEWS RELEASE, Silver improves the efficiency of monograin layer solar cells

EurekAlert NEWS RELEASE 10-DEC-2019
Silver improves the efficiency of monograin layer solar cells



Marit Kauk-Kuusik

Tenured Associate Professor

 Head of the lab


Maarja Grossberg-Kuusk

Professor, Director of the Department


Jüri Krustok

Professor Emeritus



Kristi Timmo

senior researcher


Olga Volobujeva

senior researcher


Valdek Mikli

senior researcher


Sergei Bereznev

associate professor


Taavi Raadik

senior researcher


Mare Altosaar

leading specialist 


Maris Pilvet



Jaan Raudoja

senior engineer


Katri Muska



Mati Danilson



Reelika Kaupmees



Elizaveta Shmagina

PhD student


Mehmet Ender Uslu

PhD student


İdil Mengü

PhD student


Katriin Kristmann

PhD student

Equipment and Services


Electron beam vacuum evaporator Vacuumservice

Electron beam gun vacuum evaporartor.

Vacuum evaporator is equiped with Cryo-Torr High- Vacuum pump, provides fast and clean pumping of all gases in the range 10 -3 to 10 -8 torr range.

Electron beam source with power rating up to 6 kW (max high voltage 10 kV) is used fore evaporation 1-6 materials from crucibles (4 cc eatch) mounted in rotable holder. Thickness of evaporated materiali is controlled by thickness monitor.

Solar simulator

Solar simulator Newport 

Solar simulator is a class AAA CW system producing AM1.5 illumination with area 10x10 cm2.


Laboratory of Thermal treatments 

4 Nabertherm Muffle Furnaces with parameters:

-        T max. 1100 ºC;

-        the Temperature Controller have memory for more than 8 regimes.

1 Lenton/1 Nabertherm tube furnaces with parameters:

-        T max. 1200 ºC;

-        Furnace tube diameter 70-90 mm;

1 two-zone hand-made tube furnace with parameters:

-        T max. 1000 ºC;

-        Furnace tube diameter 35 mm;

Possibility to perform quartz-tubes and all other quartz work:

-        different ampoules

-        sample holders

-        tools

etc. small quartz equipment

DTA seade

DTA Differential Thermal Analysis NETZSCH

Simultaneous Thermogravimetry - Differential Scanning Calori-metry - STA (TG-DSC) to a single sample in an STA 449 F3 Jupiter (NETZSCH) instrument yields more information than separate application in two different instruments: The test conditions are perfectly identical for the TG and DSC signals (same atmos-phere, flow rate, vapor pressure on the sample, heating rate, thermal contact to the sample crucible and sensor, radiation effect, etc.). The analyzability of the signals is improved, since two or more sets of information concerning sample behavior are always simultaneously available (differentiation between phase transformation and decomposition, between addition and condensation reactions, recognition of pyrolysis, oxidation, and combustion reactions, etc.). Maximum mass of the sample together with crucible can be 35 g. Possible heating range 25-1500 oC and rates 0.1-10K/min can be applied. Closed systems can be investigated in quartz ampoules.

Sputtering 1
Sputtering 2

Sputtering systems

SErgei vacuum

High vacuum evaporation (HVE) system  BOC-EDWARDS AUTO-500 

HVE system gives possibilities to deposit uniform layers of sublimable materials onto rotated and heated substrates in high vacuum. Size of substrates: three 7×9 cm or multiple small substrates.

Maximum substrate temperature: 500 °C. Operating pressure: 1·10-6 mBar. Four evaporation sources: 2 high temperature resistive boats + 2 crucibles with regulative temperature (till 500 °C). Thickness control of evaporated films (2 QCM sensors).


Pulsed Laser Ablation system

CVD ahi

CVD system


XPS and UPS spectometer
Kratos, AXIS-Ultra-DLD

The AXIS Ultra DLD system is a high performance electron spectrometer combining state of the art XPS functionality, including superior energy resolution and highest sensitivity to analyse the chemical composition of the studied materials surface (2 to 8 nm in depth). Standard features are small spot and parallel imaging XPS, with Ion sputtering and UPS options.

The system is equipped with standard achromatic dual anode Mg Kα(1253.6eV)/Al Kα(1486.6eV) and monochromatic single anode Al Kα(1486.6eV) X-ray sources. For UPS option the system is equipped with a windowless discharge lamp optimised for He (I) (21.2eV) or He (II) (40.8eV) output.

Multiple sample coordinates (maximum sample holder dimensions 130mm long and 15mm width) may be stored and recalled for fully automated sample analysis.

PL system

Photoluminescence system

PL system operates at wavelengths 300-3000nm and temperatures 10-300K. Different lasers are available for excitation, among them 100mW He-Cd laser with wavelengths 442 and 325 nm.


µ-Raman spectrometer  HORIBA LabRAM 800HR

Micro-Raman spectrometer HORIBA LabRAM 800HR enables to perform measurements in the region 50 cm-1 – 4000 cm-1. Two lasers with wavelengths of 532 nm ja 633 nm can be used for excitation. Following objectives are available: 100x, 50x, 50x LWD, 10x. Temperature dependent measurements can be made from 77 K to 325 K. Equipment enables to perform Raman mapping and micro-photoluminescence measurements in visible spectral region (Si CCD detector).


Capacitance spectroscopy systems  Autolab PGSTAT30 and Wayne Kerr 6500B

Autolab PGSTAT30 and Wayne Kerr 6500B are suitable for p-n junction impedance spectroscopy and current-voltage measurements.

Autolab can be used to scan voltage in a range ±10V and measure currents in a range ±1A, and to measure impedance spectroscopy in a frequency range from 10μHz to 1MHz. Autolab offers the possibility to use it as the potentiostat/galvanostat to apply constant potentials and measure currents (or vice versa with galvanostat option).

Wayne Kerr can be used to measure impedance spectroscopy in a frequency range from 20Hz to 10MHz.

Both systems can be used to measure impedance-frequency dependences at a constant potentials (in dependence of temperature T=8-300K to detect the defect energy) or impedance-voltage dependences at a constant frequences (to detect the defect concentrations).


Atomic Force Microscope (AFM)   Bruker MultiMode 8 AFM with Application Module based on Nanoscope V controller

 MultiMode 8 includes many scanning modes with new features and accessories. 

Bruker’s innovative PeakForce Tapping technology has assisted new scanning modes that give information about not only topographic but also electrical and materials properties data in parallel.

MultiMode 8 Specifications:

 Scanner Scan size          Vertical range

 ‘E’ 10μm x 10μm                    2.5μm

 ‘J’ 125μm x 125μm                5.0μm

Image Resolution: 512 Lines/pixels

Imaging Noise Level : <0.3Å RMS (Z noise using Tapping Mode in air at zero scan size

Maximum Sample Size: 15mm diameter x 5mm thick


HR-SEM  Zeiss FEG-SEM Ultra-55

FEG-SEM thermionic field emission gun SEM

Resolution 1 nm.

Imaging regimes:

SE- secondary electrons

BE- back-scattered electrons

ISE In-lens secondary electrons

IBE- In-lens back-scattered electrons

EBIC- electron beam induced current

Analysing methods

EDS energy dispersive X-ray microanalysis, Bruker Esprit 1.8 system, for determination of chemical elements composition and distribution

EBSD electron back-scatter diffraction, Oxford Instruments Channel 5 system, for determination of chemical compounds and their distribution

EDXRF energy dispersive X-ray fluorescence, Bruker EDXRF system, for determination of chemical elements composition and distribution

Devices for samples preparation

Magnetron sputtering device Quorum Q150RS for coating of the samples with conducting Au- Pd layer;

Automatic grinding –polishing machine Buehler Ecomet/Automet 250, for preparation of metallographic cross-sectional polishes;

Vibro-polishing machine Buehler Vibromet for polishing the samples for EBSD analysis;

Precision ion etching coating system Gatan PECS 682 for etching of the samples with Ar ions and for coating of the samples with thin (0,1-10 nm) layers (Au, Pd, Pt, C, etc)



MERLIN with the GEMINI II column combines ultra fast analytics, high resolution imaging using advanced detection modes, and future assured configuration flexibility on one single system.

Thanks to the prealigned GEMINI II optics imaging setting such as voltage or probe current can be seamlessly adjusted across orders of magnitudes to match your application and sample with next to no need for realignment. Even novice users will enjoy optimum results. System optimization for high current density, probe currents up to 300 nA, and superior resolution at high beam currents, guarantees fast results in nano-analytics.

Receive maximum information from your sample with parallel on-axis in-lens secondary electron (SE) and energy selective backscattered (EsB) detection capable of identifying smallest differences in materials composition.

Key Features

·    Ultra high resolution imaging at low kV

·    Ideal for precise boundary, feature, and particle measurements

·    High efficiency EsB detector for compositional information

·    High efficiency In-lens SE detector for high contrast surface imaging 

·    BSE imaging with the AsB-detector (Angle Selective BSE-Det.) at very short working distances - 1mm WD 

·    Ultra stable high current mode for x-ray analysis and EBSD applications

·    Large five axes motorised eucentric stage 

Easy operation through Windows® XP based SmartSEMTM control software

katood PL

SEM-Raman-CL measurement system  Renishaw inVia Raman and Zeiss’s EVO MA10 SEM

Integrated SEM-Raman-CL measurement system combines Renishaw’s in-Via Raman spectrometer and Structural and Chemical Analyzer (SCA), and  Zeiss’ s EVO MA10 SEM. The measurement system enables to perform Raman and cathodoluminescence measurements inside SEM. Raman measurements can be performed in the region 100 cm-1 - 4000 cm-1. CL measurements can be perfomed in IR (InGaAs detector) and visible (Si detector) spectral regions. 514 nm laser is used for excitation. The system can be combined also with liquid nitrogen cooling stage.


UV-VIS-NIR spectrometer Cary 5000


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