Perovskite solar cells (PSC) have shown that under laboratory conditions they can compete with established photovoltaic technologies. However, controlled laboratory measurements usually performed do not fully resemble operational conditions and field testing outdoors, with day‐night cycles, changing irradiance and temperature. In this contribution, the performance of PSCs in the rooftop field test, exposed to real weather conditions is evaluated. The 1 cm2 single‐junction devices, with an initial average power conversion efficiency of 18.5% are tracked outdoors in maximum power point over several weeks. In parallel, irradiance and air temperature are recorded, allowing us to correlate outside factors with generated power. To get more insight into outdoor device performance, a comprehensive set of laboratory measurements under different light intensities (10% to 120% of AM1.5) and temperatures is performed. From these results, a low power temperature coefficient of −0.17% K−1 is extracted in the temperature range between 25 and 85 °C. By incorporating these temperature‐ and light‐dependent PV parameters into the energy yield model, it is possible to correctly predict the generated energy of the devices, thus validating the energy yield model. In addition, degradation of the tested devices can be tracked precisely from the difference between measured and modelled power.
In monolithic tandem solar cells, current−voltage (J−V) characteristics of subcells provide invaluable information about their quality and tandem operation. However, accessing the subcell J−Vs is challenging and requires sophisticated spectral methods. Herein, a customized, bichromatic light emitting diode setup (BCLED) for in‐depth analysis of tandem solar cells, suitable for subcell operation analysis, and long‐term stability testing is presented. For this, two spectrally independent LED arrays are used to selectively bias the two subcells. The power of the developed setup is demonstrated by successfully disentangling the tandem J−V curve into subcell J−V curves. The method is based on a one‐diode model for each subcell and is validated by electrical simulations. Afterward, it is used on a fabricated 27.6% efficient perovskite/silicon tandem device, resulting in great agreement with the measured J−V curve. Therefore, the BCLED setup is a versatile tool, suitable for subcell characteristics and long‐term stability analysis of tandem solar cells.
a b s t r a c tThis paper describes how to select a passive load which would the most accurately follow the maximumpower-point (MPP) of small laboratory size solar cells installed outdoors in Central Europe. Either resistor or diode type of passive load have been used as a low-cost alternative to active MPP trackers (designed especially for a long-term outdoor stability study of different types of small size laboratory solar cells). The dye-sensitized solar cells have been chosen as a representative case since they exhibit similar current-voltage (I-V) characteristics dependence at different light intensities (G) and cell temperatures (T C ) as other solar cell's technologies. The results showed that the most efficient tracking was achieved when the I-V characteristic of the optimal resistor or diode cross the MPP of the solar cell measured at G = 73 mW/cm 2 and T C = 25°C. A significantly better tracking could be obtained when instead of a resistor an optimal diode is used; the optimal diode consumes 96.5% of the annual energy that would be potentially produced by the solar cell connected to ideal MPP tracker while the optimal resistor consumes only 83.5% of that energy.
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