An advanced LBIC measurement for solar cell local characterization, called CELLO has been developed and tested on mono-and multi-crystalline Si solar cells. A solar cell is illuminated with near to 1.5 AM light intensity and additionally subjected to an intensity modulated and scanning local illumination by a focused IR-laser. The linear response (current or potential) of the solar cell is measured for various fixed global conditions (different preset voltage or current values) during scanning. A large number of independent data with high spatial resolution are obtained. Applying an advanced fitting procedure on these data yields a set of local parameters for each point on the solar cell which give information on the spatial distribution of the photo current, the series and shunt resistance, the lateral diffusion of minority carriers, the quality of the back surface field and even allows the calculation of local IV-curves. The theoretical and experimental approach to this technique will be discussed and the applicability of this new solar cells characterization tool will be demonstrated.

The local thermal conductivity, thermal diffusivity, and volumetric heat capacity of cesium lead chloride perovskite thin films are mapped simultaneously and with highest spatial resolution by a scanning near-field thermal microscope. Both, the 3D phase (CsPbCl 3 ) and the 0D phase (Cs 4 PbCl 6 ) are investigated. For CsPbCl 3 thin films the variation of the thermal properties across the phase transitions in the range from room-temperature to 65°C are analyzed. While the thermal conductivity at room temperature is ultra-low, a significant increase of the thermal conductivity is found for the cubic phase of CsPbCl 3 (T>46°C). While only slight variations in the thermal conductivity are detectable for transitions from the monoclinic to the orthorhombic to the tetragonal phase, thermal diffusivity and volumetric heat capacity measurements are extremely sensitive to the amount of heat involved in the respective transition. It is shown that upon transition to the cubic phase of CsPbCl 3 thin films, the relative increase of the volumetric heat capacity is significantly higher than that of the thermal conductivity. Thus, the thermal diffusivity in the cubic phase becomes notably lower in comparison to that of the respective phase at room temperature. An increase of the volumetric heat capacity had been theoretically predicted earlier but could not be confirmed in previous experimental studies. The findings of our thermal analysis are of great general importance for fundamental material research and for the thermal design of thin-film devices based on CsPbCl 3 perovskites.

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