Fast camera-based luminescence-imaging measurements on perovskite solar cells are presented. The fundamental correlation between the luminescence intensity and the open circuit voltage predicted by the generalised Planck law is confirmed, enabling various quantitative methods for the detection of efficiency-limiting defects to be applied to this new cell structure. Interstinegly, it is found that this fundamental correlation is valid only for light-soaked devices.

To operate photovoltaic power plants at maximum capacity, it is desirable to identify cell or module failures in the field at the earliest possible stage. Currently used field inspection methods cannot detect many of the electronic defects that can be revealed with luminescence-based techniques. In this work, photoluminescence images are acquired using the sun as the sole illumination source by separating the weak luminescence signal from the much stronger ambient sunlight signal. This is done by using an appropriate choice of optical filtering and modulation of the cells' bias between the normal operating point and open circuit condition. The switching is achieved by periodically changing the optical generation rate of at least one cell within the module. This changes the biasing condition of all other cells that are connected to the same bypass diode. This method has the advantage that it can deliver high quality images revealing electrical defects in individual cells and entire modules, without requiring any changes to the electrical connections of the photovoltaic system.

Monitoring the performance of solar modules in a photovoltaic system is critical in order to understand the health of the system. Existing methods for field inspection have limited capability of detecting various electronic defects that can, however, be identified with luminescence‐based methods. A contactless outdoor photoluminescence‐imaging based measurement method that uses the sun as the excitation source was presented in our earlier work. This paper extends our previous work and presents two unique applications to (a) identify and quantify local areas of high series resistance within the cells and (b) identify bypass diodes that have failed in open‐circuit. The paper also discusses specific technical considerations of this method. The main merit of this method is that it can be used when the module is under normal operation in the field, without requiring changing of the electrical wiring of the photovoltaic array.

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This paper discusses the influence of different solar cell loss mechanisms at low light intensities and presents a simple method for the analysis of solar cell performance under various illumination intensities below 1 sun. Suns-PL and Suns − V o c are used to measure the intensity-dependent pseudo I-V curves of symmetric test structures and of finished silicon solar cells in an intensity range between 1 sun and 10 −3 suns. The solar cell parameters from the pseudo I-V curves are compared with the parameters evaluated by intensity-dependent measurements of the whole I-V curve. The pseudo efficiency and pseudo fill factor are found to be in good agreement with the real values at low intensities as the influence of the series resistance vanishes. Based on this finding, we compare the passivation quality of silicon dioxide and silicon nitride in combination with emitter windows on test structures. Above 0.1 suns, both passivation layers show similar performance. Below 0.1 suns, the pseudo fill factors and pseudo efficiencies of the silicon nitride passivated sample are strongly reduced compared with the sample with silicon dioxide. The open-circuit voltage starts differing below 0.01 suns. Index Terms-Emitter windows, intensity dependence, low light intensities, pseudo I-V curve, suns-PL, suns-V o c .