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We report a multi-modal study of the electrical, chemical and structural properties of a kesterite thin-film solar cell by combining the spatially-resolved X-ray beam induced current and fluorescence imaging techniques for the evaluation of a fully functional device on a cross-section. The data allowed the correlation of the chemical composition, defects at interfaces and inhomogeneous deposition of the layers with the local charge-collection efficiency of the device. We support our observations with Monte Carlo simulations of high-energy X-ray interactions with the semiconductor device, and finite-volume modeling of the charge-collection efficiency. [ABSTRACT FROM AUTHOR]

In an effort to understand recent results showing differences between the power conversion efficiencies of lead halide (CH3NH3PbI3−xClx) solar cells on glass versus flexible substrates, this study investigates the influence that substrate and processing methods have on morphological and crystallographic development. Using our in situ slot-die micro roll-to-roll coater setup, we measured small and wide angle X-ray scattering in grazing incidence while the material dried, enabling us to follow the crystallization from just after the deposition and up to 25 minutes later. The data showed differing crystallographic developments between the substrates, especially seen through the behaviour of a crystalline precursor which survived longer on the flexible substrates than on glass. Additionally, the common degradation product PbI2 was absent on the thickest flexible substrate. This leads us to conjecture that the flexible substrates absorb part of the solvent, thereby delaying evaporation and changing the solvent environment around the perovskite. As a further test, we produced solar cells with the same substrates and confirmed that the ones made on flexible substrates performed worse than those made on glass, but that when including an ITO layer in the stack it seemed to act as a buffer, whereby the solar cell performance was improved. [ABSTRACT FROM AUTHOR]

PEDOT-Tos is one of the conducting polymers that displays the most promising thermoelectric properties. Until now, it has been utterly difficult to control all the synthesis parameters and the morphology governing the thermoelectric properties. To improve our understanding of this material, we study the variation in the thermoelectric properties by a simple acido-basic treatment. The emphasis of this study is to elucidate the chemical changes induced by acid (HCl) or base (NaOH) treatment in PEDOT-Tos thin films using various spectroscopic and structural techniques. We could identify changes in the nanoscale morphology due to anion exchange between tosylate and Cl− or OH−. But, we identified that changing the pH leads to a tuning of the oxidation level of the polymer, which can explain the changes in thermoelectric properties. Hence, a simple acid–base treatment allows finding the optimum for the power factor in PEDOT-Tos thin films. [ABSTRACT FROM AUTHOR]

The effect of twelve different additives on organic solar cells with an active layer based on poly-3-hexylthiophene (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) has been studied in this work and tested for suitability in roll-to-roll slot-die coating. Three of the twelve additives increased the solar cell efficiency while the rest showed no effect or a negative influence on the efficiency and coatability. In cases where the additive caused an increase in performance the relation to surface topography and the structure was investigated using Atomic Force Microscopy (AFM), UV-Vis Spectroscopy and Small Angle X-ray Scattering (SAXS) for cells prepared with 1-chloronaphthalene (CN), N-methyl-2-pyrrolidone (NMP) and 1,3-dimethyl-barbituric acid (BARB) as processing additives. The studies suggested that the use of these additives resulted in films with improved morphology and electrical properties of the active layer. The effect of the CN on structural evolution during different solvent evaporation and annealing times was further investigated with an in situ roll-to-roll X-ray study. Lifetime studies under continuous illumination were used to assess the impact of the additives on the stability of the prepared devices that had an active area of 1 cm2. [ABSTRACT FROM AUTHOR]