The efficiency of perovskite solar cells (PSCs) is advancing rapidly, yet their sensitivity to am... more The efficiency of perovskite solar cells (PSCs) is advancing rapidly, yet their sensitivity to ambient conditions poses challenges. An additional degradation mechanism, potential-induced degradation (PID), can emerge during field operation, but the understanding of PID within perovskite devices is limited. To exclude environmental stressors, this study is conducted in an inert environment at room temperature. PSCs and mini-modules are subjected to a 324 h PID stress test at −1000 V, revealing relative efficiency losses of around 29% and 24% for the PSCs and mini-modules, respectively, exposing subtle degradation differences. These degradation rates are notably lower than reported in the literature, suggesting possible additional degradation pathways arising from suboptimal encapsulation combined with ambient conditions. Subsequently, half of the stressed samples are subject to +1000 V for 523 h and recover to a reduced efficiency loss of 15% and 7.7% for the PSCs and module, respectively. In contrast, storing the stressed samples on the shelf increased the efficiency losses to 32% (PSCs) and 41% (module). Therefore, the post-PID rates differ significantly between both groups, whereas both effects of voltage recovery and progressed degradation are more pronounced in modules compared to cells. This study contributes to a robust method for PID research.
A high voltage degradation mechanism on photovoltaic (PV) modules called potential-induced degrad... more A high voltage degradation mechanism on photovoltaic (PV) modules called potential-induced degradation (PID) has gained a lot of attention since 2010 when Solon published their findings about PID [1]. The research conducted on PID mainly focused on industrial scale PV systems where potential differences between the solar cell and the grounded frame in the order of 1000 V and even more are not uncommon [2–5]. In this work, a stress test for PID according to the foil method as described in IEC 62804-1 and a recovery test in the same conditions on a set of five one-cell laminates is performed. However, by stressing the one-cell laminates at different voltages (-200 V, -600 V and -1000 V) and curing them at +500 V, which is compliant with residential voltages in the PV market, and +1000 V as a reference, more insight on the impact of stress and curing voltage on PID is gained. This is the basis for a voltage dependent model for PID. Furthermore, it is shown that the impact of the stress voltage on PID as a function of time exhibits a complex behaviour. At last, the impact of PID at different stress voltages on the different operational parameters of the one-cell laminates and their physical meaning is described.
Synthetic diamond is regarded as a promising material for biosensors: it forms a stable platform ... more Synthetic diamond is regarded as a promising material for biosensors: it forms a stable platform for genetic assays and its biocompatibility opens the possibility for in vivo sensing. In this study the use of a thymidine linker for covalent DNA attachment was evaluated. Contact angle measurements provided a qualitative test of the initially oxidized surface. X-ray photoemission spectroscopy was used for further analysis of the oxides and for monitoring the effect of subsequent chemical treatments. The presence of FITC-labelled DNA was confirmed by confocal fluorescence microscopy. Enzyme linked immunosorbent assays indicated that this DNA was merely adsorbed on the diamond surface instead of covalently bound.
Abstract A round robin test was carried out in four PV laboratories to compare accelerated lifeti... more Abstract A round robin test was carried out in four PV laboratories to compare accelerated lifetime testing. Twenty commercial non-packaged CIGS solar cells of similar performance were spread and exposed to damp heat conditions (85 °C and 85% RH) for approximately 500 h. Their JV performance was monitored during the damp heat exposure. After the test, three of the labs reported average efficiency losses of 87 ± 4%, 89 ± 5% and 92 ± 1%, which are close to median degradation rates found in literature. A higher degradation rate (efficiency loss of 97 ± 3% after only 143 h) was observed in the fourth lab. This was attributed to a poorly designed ceiling window sealing, which caused liquid water pooling on the samples. After modifying the climate chamber, the experiment was repeated with similar samples and an efficiency loss of 72 ± 6% after 475 h was observed for this lab.
Near-infrared photodetection is valuable for numerous scientific, industrial and recreational app... more Near-infrared photodetection is valuable for numerous scientific, industrial and recreational applications. The implementation of organic semiconductors in near-infrared photodetectors offers additional advantages, such as printability on flexible substrates, reduced manufacturing costs and facile tuning of the detection range. In this work, the nature-inspired bay-annulated indigo (BAI) dye is employed as a building block for near-infrared sensitive, push-pull type conjugated polymers. The electron-deficient BAI moiety is copolymerized with a set of electron-rich monomers, affording polymers with an absorption onset up to 1300 nm and a sufficiently high lowest unoccupied molecular orbital, allowing electron transfer to standard fullerene acceptors. Bulk heterojunction type organic photodetectors are fabricated and the resulting device characteristics are analysed. The best performing photodetector is based on the polymer PTTBAI comprising thieno[3,2-b]thiophene as the electron-rich moiety. It has a superior light to dark current ratio, with a dark current density of 10-7 A/cm², resulting in a (shot-noise limited) detectivity of 10 12 Jones at-2 V bias within the spectral window of 600−1100 nm, exceeding the detectivity of conventional silicon CCD photodetectors in the near-infrared region (~10 11 Jones).
Building-Integrated Photovoltaics (BIPV) replace traditional building elements with power generat... more Building-Integrated Photovoltaics (BIPV) replace traditional building elements with power generating elements through the use of solar cells. One of the targets for this technology is to place the module-level power converter into the photovoltaic module's frame to achieve an integrated system. Temperature is the most influential parameter for a converter's reliability, its damage caused on the components needs to be studied in detail. In this paper, a reliability comparison based on a four-day mission profile has been made in order to assess the most reliable frame position for this converter to be placed in as all of them possess a different temperature profile. The results show that placing the converter in the lateral bottom of the frame is significantly more reliable than the mid or top position. In addition, a lifetime analysis is performed on the converter's dc-link capacitor in order to demonstrate the required methodology. In future work, this can be extended towards other sensitive components when appropriate lifetime models become available. These lifetime estimations can then be combined to achieve an overall BIPV system lifetime assessment.
Reliability of DC-DC converters is important in photovoltaic (PV) applications like building inte... more Reliability of DC-DC converters is important in photovoltaic (PV) applications like building integrated PV systems, where the module-level converter may be stressed significantly. Understanding and predicting the most failing components with accurate degradation models in such systems enables the design for reliability. In this paper, a photovoltaic mission profile-based reliability analysis framework is proposed where the inputs and models of the framework can be adjusted according to the converter topology, the components and the failure mechanisms under investigation. The framework is demonstrated by comparing the influence of two different one-year mission profiles on the solder joint degradation of a MOSFET in an interleaved boost converter. This is done by using an electro-thermal circuit simulation in PLECS and a finite element MOSFET model in COMSOL. In future work, the mesh and the geometry of the solder joint can be adjusted to more closely match the practical stress-cycle (S-N) curve used to determine the lifetime. This framework allows for exploring more accurate models or even simplify parts with low sensitivity in order to obtain a thorough understanding of their accuracy and to determine the overall converter reliability.
2017 IEEE International Reliability Physics Symposium (IRPS)
Potential-induced degradation (PID) of photovoltaic (PV) modules gets a lot of attention since 20... more Potential-induced degradation (PID) of photovoltaic (PV) modules gets a lot of attention since 2010 when Solon published their findings about a degradation mechanism in their PV modules caused by high potential differences between the solar cell and the grounded frame [1]. Module level efficiency drops of 30% and more caused by PID have been reported [2], [3]. A stress test for PID according to IEC 62804 and a recovery test in the same conditions were conducted on a set of 49 commercially available PV modules. In this paper we report the irreversibility of highly affected (i.e. over 85% PID) PV modules. From this point of view, it is important to detect and recover PID before the point of no return. Furthermore, the impact of PID on the different parameters of a PV module and their relevance in order to detect PID in the field are reported.
An alternative energy source that has appeared beyond expectations and has seen a lot of progress... more An alternative energy source that has appeared beyond expectations and has seen a lot of progress is the fuel cell. A proton exchange membrane (PEM) fuel cell is chosen for analysis and requires a DC-DC boost converter as an interface between the fuel cell and the load to provide a high-gain regulated voltage. Although great effort towards developing different converter topologies has been made during recent decades, less attention has been devoted to the reliability and thermal performance assessment of the present converters. In this paper, five non-isolated DC-DC converters are analyzed in terms of both thermal behavior and reliability. The temperature estimation of semiconductor devices as a critical part of the thermal analysis has been made via a detailed thermal model and the reliability is evaluated by means of a power cycling test. Finally, a performance score has been attributed using the TOPSIS ranking methodology and considering all the criteria (e.g., the number of comp...
Reliability of DC-DC converters is important in photovoltaic (PV) applications like building inte... more Reliability of DC-DC converters is important in photovoltaic (PV) applications like building integrated PV systems, where the module-level converter may be stressed significantly. Understanding and predicting the most failing components with accurate degradation models in such systems enables the design for reliability. In this paper, a photovoltaic mission profile-based reliability analysis framework is proposed where the inputs and models of the framework can be adjusted according to the converter topology, the components and the failure mechanisms under investigation. The framework is demonstrated by comparing the influence of two different one-year mission profiles on the solder joint degradation of a MOSFET in an interleaved boost converter. This is done by using an electro-thermal circuit simulation in PLECS and a finite element MOSFET model in COMSOL. In future work, the mesh and the geometry of the solder joint can be adjusted to more closely match the practical stress-cycle (S-N) curve used to determine the lifetime. This framework allows for exploring more accurate models or even simplify parts with low sensitivity in order to obtain a thorough understanding of their accuracy and to determine the overall converter reliability.
The combination of increasing operational voltages beyond 1000 V in photovoltaic (PV) installatio... more The combination of increasing operational voltages beyond 1000 V in photovoltaic (PV) installations and the emergence of new PV technologies requires a critical assessment of the susceptibility to potential-induced degradation (PID). Since this failure mode can trigger significant and rapid power losses, it is considered among the most critical failure modes with a high financial impact. Insights in the physical mechanism of the performance loss and its driving factors are critical to develop adapted characterization methods and mitigation solutions. PID in p-type solar cells is triggered by sodium (Na) that diffuses into stacking faults of the silicon lattice, causing shunt paths through the pn-junction. In addition, it is hypothesised that for bifacial p-PERC solar cells positive charges, such as Na + , accumulate in/on the negatively charged AlO x rear passivation layer due to the potential difference between the glass and the rear cell surface. This significantly increases surface recombination. However, the degradation behaviour observed in bifacial monocrystalline p-PERC solar cells under PID stress from both sides (bifacial PID stress) does not match with just one of the degradation mechanisms. A comprehensive test matrix was carried out to understand the physical origin of PID in front emitter bifacial p-PERC solar cells in a glass/glass packaging. The results show that bifacial p-PERC solar cells under bifacial PID stress suffer from both shunting of the pn-junction and increased surface recombination at their rear side. Hereby, we prove that the glass/glass packaging in combination with bifacial solar cells can significantly increase the severity of PID.
This paper examines the practical challenges of simplified setups aimed at achieving high-power I... more This paper examines the practical challenges of simplified setups aimed at achieving high-power IGBTs’ IC–VCE curve. The slope of this I–V curve (which is defined as on-resistance RCE) and the point where the VCE–VGE curve visibly bends (threshold gate voltage) can be suitable failure precursor parameters to determine an IGBT’s health condition. A simplified/affordable design for these specific measurements can be used for in-situ condition monitoring or field testing of switching devices. First, the possible I–V curve measurement methods are discussed in detail in order to prevent self-heating. The selected design includes two IGBTs in which the high-side IGBT was the device under test (DUT) with a constant gate voltage (VGE) of 15 V. Then, the low-side IGBT was switched by a short pulse (50 μs) to impose a high-current pulse on the DUT. The VCE–VGE curve was also extracted as an important failure-precursor indicator. In the next stage, a power-cycling test was performed, and the i...
The efficiency of perovskite solar cells (PSCs) is advancing rapidly, yet their sensitivity to am... more The efficiency of perovskite solar cells (PSCs) is advancing rapidly, yet their sensitivity to ambient conditions poses challenges. An additional degradation mechanism, potential-induced degradation (PID), can emerge during field operation, but the understanding of PID within perovskite devices is limited. To exclude environmental stressors, this study is conducted in an inert environment at room temperature. PSCs and mini-modules are subjected to a 324 h PID stress test at −1000 V, revealing relative efficiency losses of around 29% and 24% for the PSCs and mini-modules, respectively, exposing subtle degradation differences. These degradation rates are notably lower than reported in the literature, suggesting possible additional degradation pathways arising from suboptimal encapsulation combined with ambient conditions. Subsequently, half of the stressed samples are subject to +1000 V for 523 h and recover to a reduced efficiency loss of 15% and 7.7% for the PSCs and module, respectively. In contrast, storing the stressed samples on the shelf increased the efficiency losses to 32% (PSCs) and 41% (module). Therefore, the post-PID rates differ significantly between both groups, whereas both effects of voltage recovery and progressed degradation are more pronounced in modules compared to cells. This study contributes to a robust method for PID research.
A high voltage degradation mechanism on photovoltaic (PV) modules called potential-induced degrad... more A high voltage degradation mechanism on photovoltaic (PV) modules called potential-induced degradation (PID) has gained a lot of attention since 2010 when Solon published their findings about PID [1]. The research conducted on PID mainly focused on industrial scale PV systems where potential differences between the solar cell and the grounded frame in the order of 1000 V and even more are not uncommon [2–5]. In this work, a stress test for PID according to the foil method as described in IEC 62804-1 and a recovery test in the same conditions on a set of five one-cell laminates is performed. However, by stressing the one-cell laminates at different voltages (-200 V, -600 V and -1000 V) and curing them at +500 V, which is compliant with residential voltages in the PV market, and +1000 V as a reference, more insight on the impact of stress and curing voltage on PID is gained. This is the basis for a voltage dependent model for PID. Furthermore, it is shown that the impact of the stress voltage on PID as a function of time exhibits a complex behaviour. At last, the impact of PID at different stress voltages on the different operational parameters of the one-cell laminates and their physical meaning is described.
Synthetic diamond is regarded as a promising material for biosensors: it forms a stable platform ... more Synthetic diamond is regarded as a promising material for biosensors: it forms a stable platform for genetic assays and its biocompatibility opens the possibility for in vivo sensing. In this study the use of a thymidine linker for covalent DNA attachment was evaluated. Contact angle measurements provided a qualitative test of the initially oxidized surface. X-ray photoemission spectroscopy was used for further analysis of the oxides and for monitoring the effect of subsequent chemical treatments. The presence of FITC-labelled DNA was confirmed by confocal fluorescence microscopy. Enzyme linked immunosorbent assays indicated that this DNA was merely adsorbed on the diamond surface instead of covalently bound.
Abstract A round robin test was carried out in four PV laboratories to compare accelerated lifeti... more Abstract A round robin test was carried out in four PV laboratories to compare accelerated lifetime testing. Twenty commercial non-packaged CIGS solar cells of similar performance were spread and exposed to damp heat conditions (85 °C and 85% RH) for approximately 500 h. Their JV performance was monitored during the damp heat exposure. After the test, three of the labs reported average efficiency losses of 87 ± 4%, 89 ± 5% and 92 ± 1%, which are close to median degradation rates found in literature. A higher degradation rate (efficiency loss of 97 ± 3% after only 143 h) was observed in the fourth lab. This was attributed to a poorly designed ceiling window sealing, which caused liquid water pooling on the samples. After modifying the climate chamber, the experiment was repeated with similar samples and an efficiency loss of 72 ± 6% after 475 h was observed for this lab.
Near-infrared photodetection is valuable for numerous scientific, industrial and recreational app... more Near-infrared photodetection is valuable for numerous scientific, industrial and recreational applications. The implementation of organic semiconductors in near-infrared photodetectors offers additional advantages, such as printability on flexible substrates, reduced manufacturing costs and facile tuning of the detection range. In this work, the nature-inspired bay-annulated indigo (BAI) dye is employed as a building block for near-infrared sensitive, push-pull type conjugated polymers. The electron-deficient BAI moiety is copolymerized with a set of electron-rich monomers, affording polymers with an absorption onset up to 1300 nm and a sufficiently high lowest unoccupied molecular orbital, allowing electron transfer to standard fullerene acceptors. Bulk heterojunction type organic photodetectors are fabricated and the resulting device characteristics are analysed. The best performing photodetector is based on the polymer PTTBAI comprising thieno[3,2-b]thiophene as the electron-rich moiety. It has a superior light to dark current ratio, with a dark current density of 10-7 A/cm², resulting in a (shot-noise limited) detectivity of 10 12 Jones at-2 V bias within the spectral window of 600−1100 nm, exceeding the detectivity of conventional silicon CCD photodetectors in the near-infrared region (~10 11 Jones).
Building-Integrated Photovoltaics (BIPV) replace traditional building elements with power generat... more Building-Integrated Photovoltaics (BIPV) replace traditional building elements with power generating elements through the use of solar cells. One of the targets for this technology is to place the module-level power converter into the photovoltaic module's frame to achieve an integrated system. Temperature is the most influential parameter for a converter's reliability, its damage caused on the components needs to be studied in detail. In this paper, a reliability comparison based on a four-day mission profile has been made in order to assess the most reliable frame position for this converter to be placed in as all of them possess a different temperature profile. The results show that placing the converter in the lateral bottom of the frame is significantly more reliable than the mid or top position. In addition, a lifetime analysis is performed on the converter's dc-link capacitor in order to demonstrate the required methodology. In future work, this can be extended towards other sensitive components when appropriate lifetime models become available. These lifetime estimations can then be combined to achieve an overall BIPV system lifetime assessment.
Reliability of DC-DC converters is important in photovoltaic (PV) applications like building inte... more Reliability of DC-DC converters is important in photovoltaic (PV) applications like building integrated PV systems, where the module-level converter may be stressed significantly. Understanding and predicting the most failing components with accurate degradation models in such systems enables the design for reliability. In this paper, a photovoltaic mission profile-based reliability analysis framework is proposed where the inputs and models of the framework can be adjusted according to the converter topology, the components and the failure mechanisms under investigation. The framework is demonstrated by comparing the influence of two different one-year mission profiles on the solder joint degradation of a MOSFET in an interleaved boost converter. This is done by using an electro-thermal circuit simulation in PLECS and a finite element MOSFET model in COMSOL. In future work, the mesh and the geometry of the solder joint can be adjusted to more closely match the practical stress-cycle (S-N) curve used to determine the lifetime. This framework allows for exploring more accurate models or even simplify parts with low sensitivity in order to obtain a thorough understanding of their accuracy and to determine the overall converter reliability.
2017 IEEE International Reliability Physics Symposium (IRPS)
Potential-induced degradation (PID) of photovoltaic (PV) modules gets a lot of attention since 20... more Potential-induced degradation (PID) of photovoltaic (PV) modules gets a lot of attention since 2010 when Solon published their findings about a degradation mechanism in their PV modules caused by high potential differences between the solar cell and the grounded frame [1]. Module level efficiency drops of 30% and more caused by PID have been reported [2], [3]. A stress test for PID according to IEC 62804 and a recovery test in the same conditions were conducted on a set of 49 commercially available PV modules. In this paper we report the irreversibility of highly affected (i.e. over 85% PID) PV modules. From this point of view, it is important to detect and recover PID before the point of no return. Furthermore, the impact of PID on the different parameters of a PV module and their relevance in order to detect PID in the field are reported.
An alternative energy source that has appeared beyond expectations and has seen a lot of progress... more An alternative energy source that has appeared beyond expectations and has seen a lot of progress is the fuel cell. A proton exchange membrane (PEM) fuel cell is chosen for analysis and requires a DC-DC boost converter as an interface between the fuel cell and the load to provide a high-gain regulated voltage. Although great effort towards developing different converter topologies has been made during recent decades, less attention has been devoted to the reliability and thermal performance assessment of the present converters. In this paper, five non-isolated DC-DC converters are analyzed in terms of both thermal behavior and reliability. The temperature estimation of semiconductor devices as a critical part of the thermal analysis has been made via a detailed thermal model and the reliability is evaluated by means of a power cycling test. Finally, a performance score has been attributed using the TOPSIS ranking methodology and considering all the criteria (e.g., the number of comp...
Reliability of DC-DC converters is important in photovoltaic (PV) applications like building inte... more Reliability of DC-DC converters is important in photovoltaic (PV) applications like building integrated PV systems, where the module-level converter may be stressed significantly. Understanding and predicting the most failing components with accurate degradation models in such systems enables the design for reliability. In this paper, a photovoltaic mission profile-based reliability analysis framework is proposed where the inputs and models of the framework can be adjusted according to the converter topology, the components and the failure mechanisms under investigation. The framework is demonstrated by comparing the influence of two different one-year mission profiles on the solder joint degradation of a MOSFET in an interleaved boost converter. This is done by using an electro-thermal circuit simulation in PLECS and a finite element MOSFET model in COMSOL. In future work, the mesh and the geometry of the solder joint can be adjusted to more closely match the practical stress-cycle (S-N) curve used to determine the lifetime. This framework allows for exploring more accurate models or even simplify parts with low sensitivity in order to obtain a thorough understanding of their accuracy and to determine the overall converter reliability.
The combination of increasing operational voltages beyond 1000 V in photovoltaic (PV) installatio... more The combination of increasing operational voltages beyond 1000 V in photovoltaic (PV) installations and the emergence of new PV technologies requires a critical assessment of the susceptibility to potential-induced degradation (PID). Since this failure mode can trigger significant and rapid power losses, it is considered among the most critical failure modes with a high financial impact. Insights in the physical mechanism of the performance loss and its driving factors are critical to develop adapted characterization methods and mitigation solutions. PID in p-type solar cells is triggered by sodium (Na) that diffuses into stacking faults of the silicon lattice, causing shunt paths through the pn-junction. In addition, it is hypothesised that for bifacial p-PERC solar cells positive charges, such as Na + , accumulate in/on the negatively charged AlO x rear passivation layer due to the potential difference between the glass and the rear cell surface. This significantly increases surface recombination. However, the degradation behaviour observed in bifacial monocrystalline p-PERC solar cells under PID stress from both sides (bifacial PID stress) does not match with just one of the degradation mechanisms. A comprehensive test matrix was carried out to understand the physical origin of PID in front emitter bifacial p-PERC solar cells in a glass/glass packaging. The results show that bifacial p-PERC solar cells under bifacial PID stress suffer from both shunting of the pn-junction and increased surface recombination at their rear side. Hereby, we prove that the glass/glass packaging in combination with bifacial solar cells can significantly increase the severity of PID.
This paper examines the practical challenges of simplified setups aimed at achieving high-power I... more This paper examines the practical challenges of simplified setups aimed at achieving high-power IGBTs’ IC–VCE curve. The slope of this I–V curve (which is defined as on-resistance RCE) and the point where the VCE–VGE curve visibly bends (threshold gate voltage) can be suitable failure precursor parameters to determine an IGBT’s health condition. A simplified/affordable design for these specific measurements can be used for in-situ condition monitoring or field testing of switching devices. First, the possible I–V curve measurement methods are discussed in detail in order to prevent self-heating. The selected design includes two IGBTs in which the high-side IGBT was the device under test (DUT) with a constant gate voltage (VGE) of 15 V. Then, the low-side IGBT was switched by a short pulse (50 μs) to impose a high-current pulse on the DUT. The VCE–VGE curve was also extracted as an important failure-precursor indicator. In the next stage, a power-cycling test was performed, and the i...
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Papers by Michael Daenen