Marko Turek

• Dr.
• Head of Department at Fraunhofer Center for Silicon Photovoltaics

Self‐assemble monolayers (SAMs) have become state‐of‐the‐art hole‐selective contacts for high‐efficiency perovskite‐based solar cells due to their easy processing, passivation capability, and low parasitic absorption. Nevertheless, for the deposition of SAMs with a monolayer thickness and a high packing density on metal oxide substrates, critical c...

Quality control in solar cell production relies on characterization methods that are fast enough to yield information on the properties of each solar cell in less than about one second. Imaging techniques such as electroluminescence (EL) are well established methods revealing spatially resolved quality mappings. Scanning techniques such as light be...

Defects in solar cell production can lead to thermal heating, posing a risk of damaging and degradation to solar modules in the field. Elevated temperatures can accelerate chemical reactions and material degradation. To address this issue, this contribution demonstrates an experimental approach to approximate the module temperature increase during...

LED-based solar simulators have been shown to provide many advantages compared to Xenon-based flashers in particular regarding the flexibility of the spectrum, flash duration and illumination intensity. Using these extended capabilities, several new inline measurement applications, such as a rapid quantum efficiency (rapid-EQE) or rapid reflectivit...

Half-cell and third-cell modules are the current module technology standard due to their enhanced electrical performance. Also, special module layouts for building or vehicle integrated photovoltaics rely on non-standard cell formats obtained by separation techniques. For either application, interdigitated back-contact (IBC) solar cells are one of...

In this Application Note, a versatile and reliable measurement system for photoelectrochemical investigations is described which aims to assist scientists in obtaining reproducible photoelectrochemical data of high quality, including the solar‐to‐hydrogen (STH) efficiency. Specifically, it addresses the parameters irradiation quality, reaction temp...

A unified schematic visualization of Si solar cell technologies as well as tandem interconnection schemes (2, 3, 4 terminal) with industrial relevance is presented based on a comprehensive literature review.

In this Application Note, a versatile and reliable measurement system for photoelectrochemical investigations is described which aims to assist scientists in obtaining reproducible photoelectrochemical data of high quality, including the solar-to-hydrogen (STH) efficiency. Specifically, it addresses the parameters irradiation quality, reaction temp...

The Laser Enhanced Contact Optimization treatment has been shown to be beneficial for yield and efficiency improvement of PERC cells in the past three years. In this contribution, we analyze the impact of the LECO treatment on three batches of industrial PERC cells by different manufacturers applying statistical data analysis. Especially a correlat...

Shingled solar cells with Electrically Conductive Adhesive (ECA) interconnection represent a technological path to make very esthetic and efficient modules with lead free interconnection technology. The reliability assessment of the interconnection stability in shingled modules is one major aspect in the material qualification for selection of prop...

The rear side of bifacial silicon solar cells can suffer potential induced degradation (PID) when subject to high voltage stress. The PID of the polarization type (PID-p) has its largest impact on the rear side short circuit current and is attributed to loss of surface passivation. In this study, PID tests at bifacial silicon solar cells reveal fas...

In this work the influence of the LECO treatment on the typical PERC degradation mechanisms was investigated. It was found that the treatment has no significant impact on the Boron-Oxygen related Light Induced Degradation and Light and elevated Temperature Induced Degradation behavior. Furthermore, it is shown that stabilized cells remain stable af...

PV modules can quickly accumulate a light hindering layer of dust on the front glass, especially in arid regions. This soiling needs to be removed regularly, often using dry brushes as water is usually not easily available to wash the panels. Repeated cleaning negatively affects the anti-reflective coating (ARC) on the glass, leading to permanent t...

State-of-the-art solar cell technologies, such as hetero-junction cells or PERC cells, exhibit a time-dependent deformation of their current-voltage characteristics in fast solar simulator measurements. This hysteresis effect is due to an increased internal capacitance. It manifests itself as a pronounced difference between I–V-curves depending on...

Microplastic detection in water samples becomes important for tracing microplastic sources. Microplastic may harm desalination facilities by blocking filters and disturbing the marine food chain. Thermoanalytical methods, such as aspyrolysis gas chromatography mass spectroscopy and spectroscopic methods like (micro) Raman spectroscopy or (micro) Fo...

Detrimental corrosive potential induced degradation at the rear side of bifacial solar cells has been found recently. This potential induced degradation effect is non-reversible and shows typical surface damages in the micrometer scale. However, also areas in the cells showing no such surface damage suffer from electrical losses. Cracks in the nano...

Screen-printed metal-semiconductor contacts as the mainstream-metallization of industrially produced silicon solar cells are currently a major topic in research, as they still show high potential for cell efficiency improvement. The Laser Enhanced Contact Optimization (LECO) process developed by the CE Cell Engineering GmbH enables the generation o...

Various types of PID with fundamentally different physical root causes have been observed recently ranging from shunting (PID‐s), corrosion (PID‐c) to degradation of surface passivation (PID‐p). In this paper, PID‐p is investigated for the first time at the rear side of bifacial silicon solar cells with enhanced time‐resolution during degradation a...

High voltage stress at the rear side of bifacial PERC cells leads to severe power losses. In contrast to monofacial PERC solar cells, reversible de-polarization related potential induced degradation (PID-p) and irreversible corrosive potential induced degradation (PID-c) can occur. Our results show that a reliable assessment of the solar cells powe...

Fine-line printing for metallic contact structures with high aspect ratios are preferred for modern solar cell metallization. The bleeding phenomenon of screen-printed pastes during the metallization can result in an impact on the solar cell performance by shading. In this work, we present an approach for the characterization of the bleeding of org...

In a PVEL survey of 2018, light-induced degradation (LID, LeTID) was identified as the defect that causes the greatest concern among investors implying severe financial risks [1]. One reason is that the defect is still relatively new and not entirely understood due to its complexity. To reduce these risks, the LeTID Norm consortium is working on a...

pp. 1–25, ISBN: 3-936338-73-6

Bifacial passivated emitter and rear cell (PERC) solar cells are promising candidates to reduce levelized cost of electricity since a rear-side power gain can be achieved with minor changes in cell production. However, in addition to the potential-induced degradation of the shunting type (PID-s), some bifacial solar cells may exhibit another degrad...

Light-induced degradation (LID) is a known crystalline silicon cell effect that becomes noticeable in the first hours of light soaking or in the first days to weeks of operation of the PV system. The potential power loss is normally less than 3 % identified in the type approval test according to IEC 61215-2:2016 during stabilization (MQT 19.1), typ...

Bifacial PERC solar cells are promising candidates to reduce levelized cost of electricity, since a rear side power gain can be achieved with minor changes in cell production. However, in addition to the potential induced degradation of the shunting type (PID s), some bifacial solar cells may exhibit another degradation related to their rear side....

Industrial bifacial PERC solar cells show a new type of potential induced degradation (PID) at the rear side. After PID stress, cells exhibit power losses about 12 %rel. The origin of the losses is traced back to a local silicon corrosion, forming hole shaped damages within the passivation layers at the rear side. More details can be found in artic...

Bifacial passivated emitter and rear solar cells (PERC+) can suffer from potential induced degradation (PID) of the rear side. Rear‐side PID tests of industrial solar cells lead to more than 12% power degradation that is not recoverable under illumination or dark storage. A microstructural root cause analysis of the rear side reveals localized spot...

The failure and loss analysis of solar cells relies on the precise determination of their electrical performance parameters. Light emitting diodes (LEDs) used as light sources in solar simulators provide a number of advantages compared to conventional Xenon-based solar simulators. In this work, we present an approach to rapidly measure the quantum...

Motivation Gaining Understanding – What we know so far? Background: PERC, LID, LeTID… Temperature dependence of degradation and regeneration Test development Requirements for reliable testing - utilIzing Currents Update of Module LeTID Benchmark LeTID standardization Impact on Energy Yield Approach and first results

Industrial bifacial PERC solar cells have been exposed to high voltage stress at the rear side. The tested cells show a potential‐induced degradation (PID) in VOC and ISC. From a front side current voltage measurement, a power loss of about 12 %rel is observed. However, without significant change in fill factor. The degradation was traced back to m...

Solar modules with half-size solar cells have the potential for becoming the new standard. The cutting of cells leads to electrical recombination losses at the cell level, which are more than compensated by reduced resistive losses as well as by current gains at the module level. At the same time, the cutting process must be optimized to avoid mech...

In the last years, significant progress has been made regarding an understanding of light induced degradation at elevated temperature observed on PERC solar cells (LeTID). Nevertheless, the detailed root cause is still under discussion. Latest results show that a similar degradation occurs by annealing lifetime samples in the dark without carrier i...

Light Induced Degradation (LID) is a well-known cell effect, impacting in the first hours of testing or first months of operation. All c-Si device types are affected, typically with less than 5% degradation. The known mechanisms (Boron Oxygen complex formation and Iron Boron pair dissociation) are identified during certification by IEC 61215:2016 s...

In December 2014, the publicly funded project "AdmMo: Advanced multi-crystalline Modules" initiated by Hanwha Q-Cells started with the partners Heraeus, Frintrup, Innolas-Solutions, Meyer Burger Germany, Wavelabs, Karlsruhe Institute of Technology, Bergakademie Freiberg, Fraunhofer CSP and Fraunhofer ISE. The content of the project, which ended on...

LID is a well known effect, impacting in the first hours of testing or first months of operation. Testing at higher temperatures of PERC devices resulted in much higher degradation levels, but slower degradation rates than BO, termed Light Induced Degradation at Elevated Temperatures (LeTID). The presentation gives an overview of known LID mechanis...

Half-cell modules are gaining an increasing market share due to their potential of increasing the module power without requiring any changes in the cell technology. However, it has turned out that different cell separation technologies can yield a similar electrical performance of the half-cells, yet leading to an entirely different mechanical beha...

Modules with partial cells show better performance compared to full-cell modules due to lower electrical losses and increased optical gains. In this paper, we compare photovoltaic (PV) modules made of full, half, and third cells with tab widths of 0.8 and 1.5 mm under moderate and desert conditions, respectively. Initially, a statistical assessment...

Solar modules convert light in wanted electricity, unwanted heat and reflected incident light. Light absorbed in the silicon of the solar cells generates free charge carriers which are converted into electricity by the photovoltaic effect. Some of the energy absorbed in free charge carriers as well as all other absorption in non-photoactive layers...

Mechanical and electrical characterization of two half-cell cutting technologies: - Laser Scribe and Cleavage (LSC) - Thermal Laser Separation (TLS)

Recent progress in the electronic quality of high-performance (HP) multicrystalline silicon material is reported with measurements and modeling performed at various institutions and research groups. It is shown that recent progress has been made in the fabrication at Trina Solar mainly by improving the high excess carrier lifetimes τ due to a consi...

Modules with partial cells have shown better performance compared to full-cell modules due to reduced electrical losses and increased optical gains. In this paper, we have compared different module concepts of full-cell, half-cell and third-cell with different tab widths of 0.8 mm and 1.5 mm in moderate and desert conditions. First, we present the...

This works presents a new functionalization concept for front glasses of PV modules and an analysis of their anti-reflective and anti-soiling properties. The described functionalization technology is based on surface structuring and modification obtained by a low cost chemical treatment. The functionalized, nanostructured surface is part of the ori...

The rear side passivation of PERC (passivated emitter and rear) solar cells implies a modified contacting approach in comparison to Al back surface field cells. This substantial modification of the rear side leads to higher cell performance but can also imply new failure and degradation mechanisms. In our work, we present a systematic approach for...

Light induced degradation can lead to a severe efficiency loss in multi-crystalline PERC solar cells depending on bulk Si material properties and solar cell processing parameters, known as mc-LID or LeTID. Various defect models have been suggested which indicate a clear distinction to BO- and FeB-LID mechanisms. Cu is known to cause light induced d...

High-performance multi-crystalline silicon material (HPmc-Si) dominates the market for casted p-type silicon. Solar cells made from HPmc-Si material might suffer from light induced degradation due to the so called sponge-LID mechanism. In this work, we present a kinetic sponge-LID model showing that the degradation follows a pairing reaction involv...

Multicrystalline silicon solar cells are plagued by different types of light-induced degradation (LID), including Sponge-LID. Sponge-LID decreases the Al-BSF cell efficiency by up to 10 %rel. and is only partially recoverable at 200°C. This contribution shows that Sponge-LID occurs at and near most grain boundaries, but only in the centre of the af...

Light‐induced degradation (mc‐LID or LeTID) can lead to a severe efficiency loss in multi‐crystalline solar cells. The underlying mechanism clearly distinguishes from known mechanisms as B‐O‐LID and Fe‐B‐LID. Various defect models have been suggested for mc‐LID mainly based on metal impurities, including Cu which is known to cause light‐induced deg...

No abstract is available for this article.

An empirical dependence of the short circuit current density Jsc as a function of the dark saturation current density J01 is proposed, which describes this dependence down to a bulk lifetime of 1 ns. This method avoids artifacts, which appear when applying the previously proposed quadratic dependence. The parameters of the new dependence are fitted...

Modules with half-cell layout show an increased efficiency due to reduced electrical losses and increased optical gains. In this work, we demonstrate that by reducing the tab width, additional benefits can be obtained and the demands for reducing costs of material consumption and higher Cell-To-Module power (CTM) ratios can be met. First, we presen...

We present a new characterization technique based on hyperspectral imaging applied to silicon wafers. It combines the measurement of spatially and spectrally resolved reflection features and a dedicated subsequent data analysis. This method allows for a rapid localization and classification of defects and contaminations on wafers. Thus, it compleme...

The output power of a solar module is the sum of the powers of all the individual cells in the module multiplied by the cell-to-module (CTM) power ratio. The CTM ratio is determined by interacting optical losses and gains as well as by electrical losses. Higher efficiency and output power at the module level can be achieved by using novel ideas in...

Light induced degradation can cause a severe loss of efficiency on multi-crystalline PERC solar cells (mc-LID) of more than 10%rel. In this work, the kinetics of the mc-LID annealing process and its temperature dependence is analyzed. It is shown that the initial efficiency can be partly restored by annealing the cell in the dark. However, the degr...

We inscribed phase gratings into the cover glass of a solar module using femtosecond laser pulses to guide light around the front side metallization. Photocurrent and efficiency of the module increased by 1 % (relative).

A non-destructive measurement technique is presented which yields cell parameters of individual solar cells of a photovoltaic module. Our method is based on the quantitative analysis of voltage dependent electroluminescence images together with the current-voltage-characteristic of the complete module. As a result, we obtain the ideality factors n1...

Half-cell modules are promising candidates for a new generation of PV-modules as the electrical losses can be reduced while the optical gains are increased. This technological approach requires a cell separation process which does not induce any significant electrical or mechanical damages on cell level. Thermal laser separation (TLS) is a damage f...

A new generation of solar simulators is based on light emitting diode illumination sources. These measurement systems offer the opportunity to adjust the light spectrum as close as possible to the AM1.5G reference spectrum. Additionally, they provide the technical basis to combine power measurements with a spectral resolved analysis. Such an applic...

The development of new photovoltaic modules relies not only on the implementation of solar cells with higher performance but also on new module concepts such as an improved light management. This can be achieved by using optimized module components, i.e. back-sheets or connectors with special optical properties. Without changing much of the module...

Half-cell modules are promising candidates for new innovative module designs as they offer major advantages. Modified connection schemes reduce the serial resistance losses yielding a higher overall module performance. The reduced size of the cells allows a more flexible module design that is needed for special applications such as implementations...

The sheet resistance of thin film structures is commonly measured using a four-point-probe setup and involves the application of geometrical correction factors depending on the sample geometry and electrode pitch. The characterization of small thin film structures in the micrometer range requires probe tip diameters and spacings that are of similar s...

It is well established that using halved silicon wafer solar cells in a photovoltaic (PV) module is an efficient way to reduce cell-to-module resistive losses. In this work we have shown that PV modules using halved cells additionally show an improvement in their optical performance, resulting in a higher current generation. We attribute this incre...

Smaller solar cells with smaller currents have the potential to reduce series resistance losses in the interconnection tabs of solar modules. Laser scribing and subsequent cleaving of cells has proved to be a high yield processes for cutting solar cells in half and appears to be an industrially compatible process. Some companies already introduce h...

Optical losses are a major source for current and power reduction in solar modules. Hence, various improvements aiming at reducing these losses have been suggested. In this work, we have evaluated the effects of anti-reflective coating, front glass thickness, polyvinyl butyral ultraviolet+ encapsulant, and light harvesting strings on the module per...

Precise knowledge of the series resistance is essential for failure and loss analysis as well as yield prediction of solar cell devices. In this work, a method which determines the current and photogeneration dependence of the series resistance without assuming any specific current-voltage characteristic for the internal diodes is presented. This a...

A quantitative evaluation of the material quality of as-cut wafers with respect to the corresponding solar cell performance is the basis for a reliable quality control. A number of techniques have been recently developed with most of them using photoluminescence (PL) images as a starting point for the application of various image processing methods...

Minority carrier lifetime measurements are a major characterization technique regarding the material quality of semiconductors. In particular, a large variety of electrically active defects can be detected at room temperature even if present in low concentrations down to 1010cm-3 only. Transient and (quasi) steady-state methods as well as combinati...

Carrier lifetime measurements are a very powerful tool in the semi-conductor material characterization as they are very sensitive to variations in the material quality. However, the measurable carrier lifetime always depends on both material and surface properties. A number of techniques have been established to separate these two contributions to...

A reliable material characterization in an early stage of fabrication is essential for further cost reduction in the photovoltaic industry. For the crystalline silicon technology, first investigations can be performed directly after cutting the Si-ingots into blocks (bricks). Thereby, valuable information about the electrical material properties ca...

The measurement of the minority carrier lifetime is a powerful tool in the field of semiconductor material characterization as it is very sensitive to electrically active defects. Furthermore, it is applicable to a wide range of samples such as ingots or wafers. In this work, a systematic theoretical analysis of the steady-state approach is present...

The reliable analysis of trace elements in silicon is of fundamental importance for the understanding of material properties and quality control of solar cells. This paper presents a demonstration of the power of two analytical techniques for the determination of trace elements in solar silicon: inductively coupled plasma mass spectrometry (ICP-MS)...

Silicon is an important semiconductor substrate for manufacturing solar cells. The mechanical and electrical properties of multi-crystalline silicon (mc-Si) are primarily influenced by the quality of the feedstock material and the crystallization process. In this work, numerical calculations, applying finite element analysis (FEA) and finite volume...

Magneto-optical properties of the ferromagnetic semiconductor GaMnAs are studied in a material-specific multiband tight-binding approach. Two realistic models are compared: one has no impurity band while the other shows an impurity band for low Mn concentrations. The calculated magnetic circular dichroism (MCD) is positive for both models proving t...

We report on electrical measurements of the effective density of states in the ferromagnetic semiconductor material (Ga,Mn)As. By analyzing the conductivity correction due to enhanced electron-electron interaction the electrical diffusion constant was extracted for (Ga,Mn)As samples of different dimensionality. Using the Einstein relation allows to...

Spintronics has attracted wide attention by promising novel functionalities derived from both the electron charge and spin. While branching into new areas and creating new themes over the past years, the principal goals remain the spin and magnetic control of the electrical properties, essentially the I-V characteristics, and vice versa. There are...

Spintronics has attracted wide attention by promising novel functionalities derived from both the electron charge and spin. While branching into new areas and creating new themes over the past years, the principal goals remain the spin and magnetic control of the electrical properties, essentially the I-V characteristics, and vice versa. There are...

We consider the electronic properties of ferromagnetic bulk Ga1-xMnxAs at zero temperature using two realistic tight-binding models, one due to Tang and Flatté and one due to Masek. In particular, we study the density of states, the Fermi energy, the inverse participation ratio, and the optical conductivity with varying impurity concentration x=0.0...

We present a linear-response theory for the thermopower of a single-electron transistor consisting of a superconducting island weakly coupled to two normal-conducting leads (NSN SET). The thermopower shows oscillations with the same periodicity as the conductance and is rather sensitive to the size of the superconducting gap. In particular, the pre...

We present a semiclassical calculation of the generalized form factor Kab(tau) which characterizes the fluctuations of matrix elements of the operators a and b in the eigenbasis of the Hamiltonian of a chaotic system. Our approach is based on some recently developed techniques for the spectral form factor of systems with hyperbolic and ergodic unde...

Regensburg, University, Diss., 2004.

We semiclassically derive the leading off-diagonal correction to the spectral form factor of quantum systems with a chaotic classical counterpart. To this end we present a phase space generalization of a recent approach for uniformly hyperbolic systems (Sieber M and Richter K 2001 Phys. Scr. T 90 128, Sieber M 2002 J. Phys. A: Math. Gen. 35 L613)....

We study the localization length lc of a pair of two attractively bound particles moving in a one-dimensional random potential. We show in which way it depends on the interaction potential between the constituents of this composite particle. For a pair with many bound states N the localization length is proportional to N, independently of the form...

We study the thermopower of a quantum dot weakly coupled to two reservoirs by tunnel junctions. At low temperatures the transport through the dot is suppressed by charging effects (Coulomb blockade). As a result the thermopower shows an oscillatory dependence on the gate voltage. We study this dependence in the limit of low temperatures where trans...