T. Zdanowicz

Photovoltaic Performance Measurements in Europe: PV-Catapult Round Robin Tests

Two sets of modules have been sent around to different testing installations across Europe, one set to laboratories performing indoor calibrations and one set to laboratories performing outdoor power and energy ratings. The results show that for crystalline and poly-crystalline devices, a very good agreement between laboratories has been achieved. A lower agreement between laboratories has been achieved for thin film devices and further need for research is identified

PV conversion of energetic photons of the solar spectrum

The nowadays quite indispensable enhancement of PV conversion efficiency cannot be obtained without new mechanisms. The most useful of these mechanisms has to appear in the front face of the device, i.e. in the emitter, so as to allow exploitation of the energetic photons of the solar spectrum. Such an improvement can be realized through a multistage PV conversion starting by primary generation (photon absorption) followed by secondary generations (hot carrier collisions with low-energy generation centers). This cascade-like process is possible, for example, in multiinterface devices containing several emitter strata. Some of these strata assume the role of primary free-carrier generation while others do the secondary free-carrier generation. We report here investigations of new mechanisms based on I(V) curves measured on test samples with different multiinterface architectures, electronic passivations, front grids, collecting electrodes and so on. The measurements have been performed under a variable intensity incident light beam conserving always its spectral (solar) composition, except for analogous measurement cycles without a UV component. The same beam intensities with a filtered UV component complemented these investigations. The measurements have been compared with those of a weak excitation from a typical halogen lamp (relatively stable flux without a UV component). The test structures show a clear improvement of the PV conversion in the UV range induced by impact ionization within the superficial nanostratum.

Experimental determination of physical parameters in CIGS solar cells

Thin-film Cu(In,Ga)Se2 (CIGS) and CdTe photovoltaic (PV) modules have the potential to become competitive to silicon PV modules both in terms of their performance as well as productions costs. However, despite of many years of investigating them, some physical processes are not well-understood yet. One of the tools which may help to discover some of these process are numerical simulations with use of equivalent diode model applied for the analysis of physical behaviour of solar cells. In the paper results of experimentally determined values of diffusion and recombination related components of diode dark saturation corresponding to double-diode model (DEM) are presented. Obtained values result from considering of p-n junction physical basics as well from numerical simulations. To fit large amount of I-V curves to one of the commonly used diode models special PC program has been developed. Its role is fast and efficient importing of I-V curves from database, immediate performing fitting procedure with subsequent storing and graphical presentation of the calculated results. Presented examples show a discrepancy between diffusion and recombination dark current components derived using both methods. The reason for this discrepancy is discussed.

Accuracy of Energy Prediction Methodologies

In the current market, the specific annual energy yield (kWh/kWp) of a PV system is gaining in importance due to its direct link to the financial returns for possible investors who typically demand an accuracy of 5% in this prediction. This paper focuses on the energy prediction of photovoltaic modules themselves, as there have been significant advances achieved with module technologies which affect the device physics in a way that might force the revisiting of device modelling. The paper reports the results of a round robin based evaluation of European modelling methodologies. The results indicate that the error in predicting energy yield for the same module at different locations was within 5% for most of the methodologies. However, this error increased significantly if the nominal nameplate rating is used in the characterization stage. For similar modules at the same location the uncertainties were much larger due to module-module variations

Optimization of the optical parameters of TiOx antireflection layers deposited by a spin-on technique

Abstract The optical properties of TiO x layers deposited by a spin-on technique with different spin speesd and baked at different temperatures have been studieed with consideration to their applicability as highly efficient antireflection coatings (ARC) for silicon solar cells. Some cells have been fabricated and both their spectral response as well a I–V curves have been measured. Cells with a TiO x ARC layer show an increase in the conversion efficiency up to nearly 40% when compared to “bare” cells, mainly due to a large increase in the short-circuit current.

PV conversion of energetic photons of the solar spectrum: Effect of the UV component

The nowadays quite indispensable enhancement of PV conversion efficiency cannot be obtained without new mechanisms. The most useful of these mechanisms has to appear in the front face of the device, i.e. in the emitter, so as to allow exploitation of the energetic photons of the solar spectrum. Such an improvement can be realized through a multistage PV conversion starting by primary generation (photon absorption) followed by secondary generations (hot carrier collisions with low-energy generation centers). This cascade-like process is possible, for example, in multiinterface devices containing several emitter strata. Some of these strata assume the role of primary free-carrier generation while others do the secondary free-carrier generation. We report here investigations of new mechanisms based on I(V) curves measured on test samples with different multiinterface architectures, electronic passivations, front grids, collecting electrodes and so on. The measurements have been performed under a variable intensity incident light beam conserving always its spectral (solar) composition, except for analogous measurement cycles without a UV component. The same beam intensities with a filtered UV component complemented these investigations. The measurements have been compared with those of a weak excitation from a typical halogen lamp (relatively stable flux without a UV component). The test structures show a clear improvement of the PV conversion in the UV range induced by impact ionization within the superficial nanostratum.

Screen-printed silicon solar cells with texturized and passivated emitter diffused from spin-on phosphorous source

Spin-on phosphorus diffusion source has been used for emitter formation in silicon solar cells. It is shown that commercially available phosphorosilicamer emulsion used for that purpose can be easily modified by adding alcohol solution of P2O5 thus allowing us to obtain junctions with different dopant profiles for the same process conditions. SIMS curves have been taken for several samples and compared with theoretical simulation of diffusion profile showing that diffusion driven from spin-on source may strongly differ from that carried out from classic POCl3 source. Results of some experiments on emitter passivation by simple dry oxidation are also presented.