35th European Photovoltaic Solar Energy Conference and Exhibition; 1165-1168,Potential induced degradation (PID) is a severe problem in a significant number of PV installations globally. Ultimately the problem is reliably resolved on cell and module level. But this is only possible for new installations and with good pre-qualification checks of components as well as checks on delivered PV modules. The presented method targets all existing PV installations having the PID problem. As of today, there are several solution providers in the market that offer PID mitigation devices. Those operate differently and will be differently effective to recover or stabilize the output power. In most cases the recovery works, at least to a certain extend. The long term impact of such devices has not been investigated yet.
The proposed test and test sequence offers a fast initial check to see the effect of alternating potentials on the PID sensitive PV module.
Based on the findings PV modules, that have been recovered successfully can grouped into two types: Modules that are stable and those that degrade in the cycling A-HVS test. The test basically indicates a potential long term risk for a PV module exposed to high alternating bias even after a first successful recovery step utilizing constant recovery potential in the field.,
Contributors:Schultz, C., Bartelt, A., Junghans, C., Schmidt, S., Schlatmann, R., Stegemann, B.
35th European Photovoltaic Solar Energy Conference and Exhibition; 870-874,Laser-based patterning of CIGSe solar cells for monolithic serial interconnection is still challenging.
Reasons are laser-induced damages resulting in alterations of the CIGSe material either due to material
inhomogeneities or improper laser patterning parameters. These alterations affect the CIGSe composition as well as
its electrical properties. In this study we focus on the electrical properties in the vicinity of the P2 lines, scribed either
by laser or needle patterning. The CIGSe films patterned by nanosecond lasers are compared to needle-patterned
CIGSe samples serving as a reference. By comparing optical microscopy images with photoluminescence intensity
images significantly wider laser-scribed lines were found in the photoluminescence images. Time-resolved
photoluminescence decay curves were analyzed for varying distances to the scribe line. For the laser-scribed samples
a significant reduction of the charge carrier lifetime is found when approaching the scribe from untreated material
areas. It is shown that the shorter charge carrier lifetimes can be related to known CIGSe lattice defect states such as
Cu vacancies and Cu anti-sites acting as recombination centers. These results provide further understanding of the
laser-material interaction and help optimizing the patterning processes for monolithic serial interconnection of CIGSe
Contributors:Sekhar, H., Fukuda, T., Tanahashi, K., Takato, H.
35th European Photovoltaic Solar Energy Conference and Exhibition; 503-506,We developed a diamond wire characterized by the core steel-wire diameter of 80 μm and the size of diamond abrasives ranging from 6 to 12 μm (labelled as 80d-M6/12). The diamond particles on the wire are designed to have lower density and less agglomeration than those on conventional wires. As-developed diamond wire is introduced into multi wire saw to cut monocrystalline silicon bricks into wafers with a thickness of 210 and 140 μm. The above wire allows us to reduce the silicon dust or kerf to 100 μm per wafer. After as-sawn wafers are separated from fresh and worn-out wire sides of bricks and labelled as fresh and worn-out wire side wafers. In three-line bending test, a variable load is applied in perpendicular direction to wire saw marks on the wafer surface. The fracture strength distributions are evaluated on fresh and worn-out wire side wafers. In thick wafers, the fracture stress distributions are approximately the same on both sides. On the other hand, in thin wafers, the fracture strength is extremely lower than that of thick wafers. And particularly, the strength of fresh wire side wafers is lower compared to that of worn-out wire side wafers. In thin wafers, a small variation in the surface and subsurface damage is a crucial factor to decide their fracture strength of both-side wafers. In case of thick wafers, a small variation in the surface and subsurface damage may not have strong influence on their fracture strength of both-side wafers.,
Contributors:Abdullah Eissa, M., Almeida Silva, J., Serra, J.M., Bassiuny, A.M., Lobato, K.
35th European Photovoltaic Solar Energy Conference and Exhibition; 2010-2013,As the installation of PV systems continues to decrease, the weight of the operation and maintenance
in the cost structure of systems will become an ever increasing factor. The significant challenges are to maximise
electrical energy production by reducing system downtime for planned and unplanned maintenance.
Electroluminescence (EL) is becoming an important on-site/infield characterization technique for PV modules.
However, proposed high-end EL systems may be too prohibitively expensive, eg, for small systems or low-income
areas. This paper demonstrates the principles a low-cost EL system for crystalline PV modules. A consumer grade
camera system (camera and lens) was modified by removal of the IR filter to allow for the band-to-band luminescent
spectra to arrive at the CCD sensor. To remove background visible light, a bandpass filter tuned to approximately
the luminescent spectra of silicon (1100+/-10nm) was placed before the camera lens. Open-source digital imaging
processing techniques were then employed to correct geometrical image distortions and to enhance image quality.
The effectiveness of the proposed system is demonstrated under three controlled conditions; indoor completely
dark, indoor with controlled background lighting and, outdoor urban night-time. The system allowed for acquisition
of high resolution EL images of PV modules in a matter of minutes. The quality of the images under the differing
conditions are comparable. Easily visible were cracks in individual cells and also non-functioning cells of a
purposefully damaged PV module.,
35th European Photovoltaic Solar Energy Conference and Exhibition; 672-675,In this study, the properties of the intrinsic amorphous silicon (a-Si:H) and p-doped microcrystalline silicon (μc-Si:H) materials were investigated in a wide range of the deposition rates using the plasma enhanced chemical vapour deposition (PECVD) technique at the very high excitation frequency (VHF) and standard radio-frequency (RF). Thereby, the high-rate and low-rate regimes were compared. The material properties of the passivation layers as well as carrier lifetime were studied. Furthermore, the new p-type μc-Si:H electrodes were introduced. The initial growth process of the p-layer on top of the a-Si:H material was developed. Additionally, the influence of the ion bombardment energy on the deposition process is studied using simulation methods. At the final stage of the development, the dynamic VHF-PECVD process for the passivation and electrode layers has been introduced and applied for a highly productive fabrication of the heterojunction silicon solar cells (HIT).,
Contributors:Zeller, U., Pander, M., Daßler, D., Jäckel, B.
35th European Photovoltaic Solar Energy Conference and Exhibition; 1312-1317,Lifecycles of products used outdoors are primarily influenced by given operating conditions. These conditions mainly vary depending on the location. Hence one, possibly, can determine one primary driver of all environmental parameters but in general a number of climatic parameters (e.g. temperature, relative humidity, wind, precipitation, UV exposure and others) have to be considered relevant. Working with real meteorological data in lifetime simulation and durability tests leads to large quantities of data. This work introduces an approach to reduce these large quantities to ensure feasible implementation in lifetime simulation by the example of finite element analysis on PV modules.,
Contributors:Fleck, M., Lindroos, J., Zuschlag, A., Hahn, G.
35th European Photovoltaic Solar Energy Conference and Exhibition; 527-530,The effects of atmospheric pressure chemical vapor deposition (APCVD) gettering on material quality of industry standard mc-Si wafers has been studied on a microscopic level and compared to POCl3 gettered samples.
The interaction of the gettering efficacy with the microscopic defect structure has been studied by a combination of measurements of the effective minority charge carrier lifetime (eff), interstitial iron (Fei), optical microscope images of defect structures revealed with Secco etching, a subsequent high resolution etch pit density (EPD) analysis as well as Electron Beam Induced Current (EBIC) and Electron Backscatter Diffraction (EBSD). Findings include a similar gettering quality of APCVD- and POCl3-based glasses and a reduction of EPD after the gettering step.,
Contributors:Alquennah, A.N., Al-Asfour, A.T.
35th European Photovoltaic Solar Energy Conference and Exhibition; 1214-1217,Bifacial (BiFi) photovoltaic (PV) modules increase the overall yield as they generate power from both sides. There has been a growing interest in developing new testing procedures to characterize BiFi devices using monofacial solar simulators. One proposed method to estimate the power generated from both sides measures the Pmax of only one side with an equivalent irradiance intensity (GE) as that of the incident irradiance on both sides. This Pmax determination technique is known as the GE method. In this study, we investigate the accuracy of the GE method in estimating Pmax by comparing the results with the sum of Pmax measured from both sides separately. Using the GE method, errors in power determination were found to be as high as 4.8%. Furthermore, using a dynamic fill factor bifaciality coefficient, instead of the proposed short-circuit current or power bifaciality coefficients, when applying the GE method improved accuracy by more than two folds.,
Contributors:John, J., Jambaldinni, S., Haslinger, M., Gocyla, M., Hajjiah, A., Kuzma-Filipek, I., Tous, L., Russell, R., Duerinckx, F., Szlufcik, J., Poortmans, J.
35th European Photovoltaic Solar Energy Conference and Exhibition; 584-586,We report on the progress of wet chemical process development for silicon surface texturing of n-type
passivated emitter with rear totally diffused (n-PERT) solar cells. A KOH-based texturing process sequence has been
developed which provides potentially both improved conversion efficiency and reduction in cost of ownership (CoO). The
improvement in conversion efficiency is attributed to decreased saturation current density after diffusion and laser
processing, whereas, reduction of CoO is reached by reduced material consumption and process time. We have determined
the saturation current density after subsequent process steps like Boron emitter diffusion, Phosphorous back surface field
diffusion, passivation, laser ablation and selective laser doping for small pyramid (pyramid base length <2μm) and standard
texturing (pyramid base length 3-5μm), respectively.,
Contributors:Järvelä, M., Lappalainen, K., Valkealahti, S.
35th European Photovoltaic Solar Energy Conference and Exhibition; 1964-1968,Due to the cloud enhancement (CE) phenomenon, global horizontal irradiance can exceed the clear sky irradiance value. Enhanced irradiance areas are formed when photons are scattering from the water droplets in clouds near the direct irradiance path. The CE is well-known as a phenomenon, but its effect on photovoltaic (PV) generators has not been thoroughly studied. Output power of a PV generator is almost directly proportional to the irradiance. Therefore, due to the CE phenomenon, output power of a PV generator can exceed the nominal power, which affects the requirements set to the inverter. We used irradiance measurement data of 440 days from an array of pyranometers to calculate the speeds and movement directions of cloud shadows to deduce the diameters of enhancement areas. During the CE events, the irradiance values were occasionally more than 150% of the expected clear sky irradiance value. We discovered that the diameters of these extreme irradiance areas are tens of meters and, therefore, they can have a full effect on residential or commercial scale PV systems. Utility scale PV generators are in practice affected more by less extreme CE events with larger diameters, since spatial smoothing by the large generator area decreases the effects of the extreme events.,