M. Prorok

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.

Analysis of the Applicability of the Diode Equivalent Model for GIGS Thin-Film Photovoltaic Modules

Equivalent electrical models, either single or double diode, of photovoltaic (PV) cells and modules can be very useful tools when predicting performance of PV devices to be operated in natural, changeable conditions. Additionally, such models may also be very helpful when analyzing even basic physical processes occurring in the devices, e.g. recombination/diffusion processes. In the paper results of numerical simulations with use of equivalent diode model applied for the analysis of Cu(In,Ga)Se2 (CI(G)S) thin-film solar cells are presented. For that purpose I-V curves systematically acquired in the outdoor monitoring system have been used. 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 effective importing of I-V curves from database, immediate performing fitting procedure with subsequent storing and graphical presentation of the calculated results. The choice which of the models, i.e. either single model or two-diode, is more appropriate for a specific I-V curve, depended on better approximation of the calculated curve to measured one according to defined criteria. Presented examples show results of using developed program and effect of chosen model on resulting module performance parameters. It is shown which model seems to be more reliable for Cu(In,Ga)Se2 thin-film solar cells, including analysis of the approximation errors

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.

Using physical parameters in predicting energy gain of CIGS PV modules

In previous works [1, 2] it was researched that the equivalent double diode model - DEM is appropriate to model Cu(InxGa1-x)Se2 (CIGS) photovoltaic (PV) modules. It was investigated with large amount of data (including current - voltage curves) collected during long-term monitoring of PV systems. Current work concentrates on applying physical parameters to model 2 of 5 DEM parameters: diffusion IS1 and recombination IS2 related components of dark diode saturation current. Modeled ISI and IS2 values replace previously approximated DEM parameters and are used to predict measured I-V curves in order to determine electrical parameters of the PV modules. The parameters are used to predict energy gain in natural working conditions. Results of modeling are presented and compared with measured data.