The mapping of the refractive index of cells has been extensively studied since 1950s. This optical parameter constitutes a key biophysical property strongly correlated to fundamental cell parameters such, e.g., intracellular mass distribution and protein concentration. Experimental studies evidence that the cell refractive index (Refractive Index) provides critical insights to understand diverse cellular structures and interpret pathological states, including diverse stages of diseases. However, measuring the refractive indices of biological specimens satisfying clinical requirements is currently challenging, since there is a lack of spectral signatures of sub-cellular components in the visible range due to their transparent nature. Designing methods capable of extracting visible fingerprints of cellular components remains attracting large research interests. In this work, I have contributed to this project by fabricating and characterizing a black nanostructured membrane that dynamically interacts with cancerous cells and furnishes label-free structural color generation by exploiting the inherent contrast mechanisms of them. Thus, adequately meeting morphology differentiation to assist in biomedical research. I have tested the system with HCT116 colorectal cancer cells. In addition, this special membrane allows refractive index recovery and cell thickness mapping with commonly available bright-field microscopy equipment. Therefore, it is of considerable clinical importance to allow the generation of qualitative information about cell morphology to add in medicine and biophysics research.

Organic solar cells have shown great promise of becoming a cheaper alternative to inorganic solar cells. Additionally, they can also be made semitransparent. To avoid using expensive indium tin oxide electrodes in organic solar cells the electrodes can be made from conductive polymer, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). However, these so-called PEDOT-PEDOT solar cells are prone to short-circuiting. The work behind this thesis thus aimed to find the cause of these short circuits. The initial working hypothesis assumed the hygroscopic PSS in the bottom electrode could attract water across the active layer when the top electrode layer was applied. This would then swell the bottom electrode and cause the active layer to crack leading to short circuits. Accordingly, swelling was investigated as it was suspected to be the main cause of the shorts. This was achieved by coating reflective substrates with different layers from the solar cell, dropping water on top of the stack and then filming the thin film interference effects. SEM, AFM and IR were also used for further analysis. Although the bottom electrode swells, it was found that water does not cause permanent cracking. Instead, the research unveiled that water causes a formation of blisters, which are suspected to be made of PSS. The exact mechanism for the formation of the shorts remains unclear however.