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Solar simulators based on light-emitting diodes (LEDs) usually consist of many spectrally different LEDs, which in sum produce a sun-like spectrum. On the one hand, this results in the advantage of a high spectral tunability of these systems and on the other hand, however, also in the challenge of a high number of parameters which have to be set for the adjustment of a suitable simulator spectrum. Multijunction solar cells consisting of series-connected subcells are very sensitive to spectral irradiance conditions, which are affecting the current and the fill factor of the device. A precise adjustment of the simulator spectrum based on the spectral responsivity of the subcells is therefore essential for accurate multijunction measurements. Therefore, the number of spectrally different light sources used should be at least as high as the number of subcells in the device under test. However, for the measurement of multijunction devices, the much higher number of spectrally different light sources in common LED solar simulators results in a plethora of different simulator spectra, potentially suitable for the measurement. Furthermore, the nonlinear intensity characteristics of the utilized LEDs as well as the distance-dependent illumination uniformity of such solar simulators add complexity when aiming for a precise spectral adjustment. To tackle these challenges, a new spectral adjustment procedure which is based on a least square's solution algorithm and the definition of appropriate boundary conditions for the calculation of suitable simulator settings is introduced in this publication. Focusing on measurements carried out under constant illumination makes the presented method especially applicable for perovskite-on-silicon multijunction devices. Therefore, an adapted method for the determination of the solar simulator's spectral properties, considering thermal influences which are particularly relevant when carrying out continuous illumination measurements, is introduced in this work. The presented method is verified applying it on a Wavelabs SINUS 220 LED solar simulator by performing a measurement comparison on a multijunction solar cell with Fraunhofer ISE CalLab's well-established multilight source solar simulator. [ABSTRACT FROM AUTHOR]

In recent years, significant progress has been made in terms of efficiency and stability of perovskite on silicon (Pero/Si) tandem solar cells. Nevertheless, most of these activities are focused on small‐area laboratory cells while the availability of large‐area solar cells suitable for module integration on an industrial level remains limited, and therefore, measurements of tandem modules are rare. However, the reliable measurement of tandem modules is a prerequisite to evaluate the real potential of this rapidly developing technology for the photovoltaic market. In this study, we present the first published outdoor measurement of a full‐size bifacial Pero/Si tandem solar cell module. Our focus is on analyzing the spectral influences on the outdoor performance of the device through a qualitative assessment of the modules I–V parameter conducted over the course of a measurement day. Based on continuous monitoring of the ambient and module conditions, we provide consistent explanations for the complex interplay between the incident irradiance on both the front and backside of the module, as well as the module temperature. Based on our findings, we finally discuss how to appropriately account for the influence of bifaciality in the case of bifacial tandem modules, where the procedures used for bifacial single‐junction devices cannot be easily applied due to subcell limitation effects. Throughout the study, we present important insights into the real‐world characteristics of a bifacial Pero/Si tandem model, discuss and explain various influences on the modules performance, and therefore provide crucial information for an optimal cell design for bifacial Pero/Si tandem devices. [ABSTRACT FROM AUTHOR]

Spectrometric characterization allows for accurate determination of the current matching point and investigation of sub‐cell properties of multi‐junction solar cells. It is widely used for dual‐junction solar cells. Although the concept is suggested for triple‐junction solar cells, it is only applied for the variation of two sub‐cells. In this work, the applicability and evaluation procedure for a systematic variation of all three sub‐cells of a triple‐junction solar cell are presented. Clearly defined measurement conditions are derived which allow for meaningful characterization and comparisons of different triple‐junction devices. The presented procedure is exemplarily tested on a III–V on silicon triple‐junction solar cell using an light‐emitting diode‐based solar simulator where all needed spectral conditions can be calculated in advance and accordingly adjusted. Spectral conditions around the air mass 1.5 global spectrum are chosen and a fit routine to determine the current matching point from the discrete measurement points is proposed and validated by a measurement with a higher resolution around the current matching point. Finally, it is shown that the spectral conditions applied during the measurement also reflect outdoor conditions. This highlights the relevance of the presented procedure beyond the determination of the current‐matching conditions. [ABSTRACT FROM AUTHOR]

In monolithic perovskite/silicon tandem solar cells, it is important to know which subcells are limiting the overall current to adapt the perovskite absorber thickness and bandgap accordingly. The current matching situation is usually analyzed by integrating measured external quantum efficiencies. However, this method can lead to significant errors and misinterpretations if metastable perovskite solar cells are involved. Herein, spectrometric characterization is presented as an alternative approach avoiding these errors. Current–voltage curves are recorded under different spectral conditions. Spectral irradiance settings are varied in a systematic way from redshifted spectra (the perovskite top solar cell limits the current) to blueshifted spectra (the silicon bottom solar cell limits the current) around the air mass 1.5 global (AM1.5G) spectrum. This method not only allows for accurate determination of the current matching point, but also gives quantitative insight in the behavior of the single subcells and their influence on the tandem performance. As different current mismatching also influences other global cell parameters, an example is presented where the current loss due to the current mismatch is partly compensated by a strong fill factor increase when the silicon solar cell limits the current, resulting in a high‐power output also at the AM1.5G condition. [ABSTRACT FROM AUTHOR]