CH3NH3PbI3 perovskite solar cells with a mesoporous TiO2 layer and spiro-MeOTAD as a hole transport layer (HTL) with three different CH3NH3I concentrations (0.032 M, 0.044 M and 0.063 M) were investigated. Strong variations in crystal size and morphology resulting in diversified cell efficiencies (9.2%, 16.9% and 12.3%, respectively) were observed. The physical origin of this behaviour was analysed by detailed characterization combining current-voltage curves with photo- and electroluminescence (PL and EL) imaging as well as light beam induced current measurements (LBIC). It was found that the most efficient cell shows the highest luminescence and the least efficient cell is most strongly limited by non-radiative recombination. Crystal size, morphology and distribution in the capping layer and in the porous scaffold strongly affect the non-radiative recombination. Moreover, the very non-uniform crystal structure with multiple facets, as evidenced by SEM images of the 0.032 M device, suggests the creation of a large number of grain boundaries and crystal dislocations. These defects give rise to increased trap-assisted non-radiative recombination as is confirmed by high-resolution μ-PL images. The different imaging techniques used in this study prove to be well-suited to spatially investigate and thus correlate the crystal morphology of the perovskite layer with the electrical and radiative properties of the solar cells and thus with their performance.

The local prebreakdown behavior of a damage etched multicrystalline silicon solar cell produced from virgin grade feedstock was characterized. At the position of micrometer-scaled prebreakdown sites, which correlate with recombination active defects found along grain boundaries, micro-x-ray fluorescence mappings revealed the presence of Fe precipitate colonies. These measurements represent direct evidence that transition metal clusters lead to decreased breakdown voltage and cause soft diode breakdown

In the last fifteen years the measurement of the spatially resolved carrier lifetime has emerged as a valuable tool for the characterization of silicon wafers and solar cells. In most of the available measurement methods, the spatial resolution is constrained to the order of several 10 to 100 µm by the diffusion length of the charge carriers. In this paper we introduce a contactless quantitative technique to determine the Shockley-Read-Hall lifetime with a spatial resolution of 1µm. This technique is based on high injection microphotoluminescence spectroscopy and allows a quantitative analysis of microscopic defects such as grain boundaries and metal precipitates by virtue of the high spatial resolution

Contact formation with silver (Ag) thick film pastes on boron emitters of n-type crystalline silicon (Si) solar cells is a nontrivial technological task. Low contact resistances are up to present only achieved with the addition of aluminium (Al) to the paste. During contact formation, Al assisted spiking from the paste into the silicon emitter and bulk occurs, thus leading to a low contact resistance but also to a deterioration of other cell parameters. Both effects are coupled and can be adjusted by choosing proper Al contents of the paste and temperatures for contact formation. In this work the microscopic electric properties of single spikes are presented. These microscopic results, i.e. alterations of the local emitter doping density, the pronounced local recombination activity at the interface between spikes and Si and its influence on the charge collection efficiency, are used to explain the observed dependencies of global cell parameters on the Al content of contact pastes

The silicon surface texture significantly affects the current density and efficiency of perovskite/silicon tandem solar cells. However, only a few studies have explored fabricating perovskite on textured silicon and the effect of texture on perovskite films because of the limitations of solution processes. Here we produce conformal perovskite on textured silicon with a dry two-step conversion process that incorporates lead oxide sputtering and direct contact with methyl ammonium iodide. To separately analyze the influence of each texture structure on perovskite films, patterned texture, high-resolution photoluminescence (μ-PL), and light beam-induced current (μ-LBIC), 3D mapping is used. This work elucidates conformal perovskite on textured surfaces and shows the effects of textured silicon on the perovskite layers with high-resolution 3D mapping. This approach can potentially be applied to any type of layer on any type of substrate.

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Microscopic laser-doped regions in advanced solar cell concepts are analyzed to determine the doping density and to identify the damage caused by the laser process. For these investigations, microphotoluminescence spectroscopy and micro-Raman spectroscopy are utilized to measure doping density, internal stress, and carrier lifetime with micrometer resolution. This analysis proves the high applicability of the microspectroscopic techniques for the characterization of laser-doped regions by analyzing the profile of the advanced local doping process and the laser-induced damage particularly at the edges of the highly doped regions.

L subcells integrated into a monolithic tandem solar cell is challenging though crucial in order to identify performance limiting loss mechanisms. This method can be used to improve the study of the mutual influence of adjacent subcells in the fully fabricated device, which has been an unfeasible task up to now.