This investigation assesses the effect of different encapsulation materials and environmental conditions on ionic currents in methylammonium lead iodide (MAPI) thin films, which are essential for the stability of perovskite solar cells. Encapsulation types such as PMMA, MgF2, and SiO2 were examined under both air and vacuum conditions, complemented by an epoxy-sealed glass cover for extra protection. Employing the photo-electromotive force technique to analyze ion dynamics, findings indicate that environmental exposure and layer interaction profoundly influence ionic activity. While a single encapsulation layer falls short in protecting against environmental factors, combining SiO2 with an epoxy-sealed glass significantly improves MAPI film stability, albeit the epoxy layer alters ionic responses, underscoring the complexity in optimizing encapsulation for enhanced solar cell performance.
In this study, we investigate the phenomenon of nearly zero reflectance and associated phase singularity in a random array of gold nanoislands (Au NI) both theoretically and experimentally. The Au NI were produced via solid-state thermal dewetting of ultrathin gold films, which were magnetron sputtered onto a glass substrate. The morphology of the nanoislands was characterized using scanning electron microscopy and atomic force microscopy. To understand the plasmonic response of the random array of Au NI, we conducted reflectance measurements for both s and p polarized beams demonstrating the p. These measurements were performed using the attenuated total internal reflectance configuration. A partial state of topological darkness in a random array of Au NI was demonstrated by showing nearly zero reflection for the p polarization component. Additionally, we employed a common path spectral interferometer to measure the differential phase spectra. Our findings revealed that the differential phase spectra exhibited abrupt ±π phase jumps, indicating the presence of a phase singularity regime. Moreover, we demonstrated high bulk reflectance index sensitivity (RIS) within this regime. To validate our experimental results, we compared them with analytical reflectance and phase spectra obtained through the application of island film theory. The agreement between the experimental and theoretical predictions provided strong confirmation of our measurement technique.
In this work, we investigate the plasmonic response of a random metasurface based on gold nano-islands (AuNI) in an attenuated total reflectance (ATR) configuration. AuNI structures were obtained by thermal annealing of an ultrathin gold film deposited on a glass substrate. The samples exhibited a wide range of sizes and particle densities, varying the nominal gold thickness. For p polarization, a well-defined localized surface plasmon resonance (LSPR) dip was observed in all samples, while for s polarization, only AuNI with the smallest radii showed this dip. Some samples exhibited nearly zero reflection at the resonance wavelength. The highest sensitivity among all tested samples was achieved in these samples, providing potential for optimizing LSPR transducers in sensing applications. Notably, the resonance wavelength exhibited a nonlinear dependence on the refractive index in sensitivity measurements displaying a blue shift.
We have demonstrated theoretically and experimentally that the current induced by an interference pattern moving at constant velocity can be used to determine the ion mobility and activation energy in perovskite semiconductors. The frequency dependence of the signal has features predicted by theory: the high-frequency peak corresponds to the electron/hole photoconductivity relaxation process, and the low-frequency peak occurs when the velocity of the interference pattern synchronizes with the ion motion; by determining the peak’s position, it becomes possible to estimate the ion mobility. The values of ion mobility and activation energy agree with the data reported in the literature.
The study of unstable interfaces in perovskite semiconductors requires crucial information on interfacial composition, chemical gradients, and impurity distribution. A versatile technique called TOF-SIMS can provide this information effectively. Solar cells employing methylammonium lead triiodide as the photoactive layer were fabricated, utilizing PEDOT:PSS or NiOx thin film as the hole transporting layer, and PCBM plus ZnO as the electron transporting layer. These inorganic and organic layers were deposited through magnetron sputtering and solution processing, respectively. To comprehensively examine each interface within the device structure, a detailed TOF-SIMS study was conducted.
Organic materials have become very important in recent years due to their potential use for photovoltaic applications. Among the main advantages of organic semiconductors are their functional and mechanical flexibility, as well as fabrication simplicity. However, these materials usually afford moderate efficiency in organic photovoltaic devices. On the other hand, hydrogenated amorphous silicon (a-Si:H) is a widely known inorganic semiconductor that compared to their organic counterparts has excellent photogeneration and transport properties and it is suitable for large area fabrication of flexible devices. The idea of combining organic semiconductors and amorphous silicon films in hybrid photovoltaic devices is very attractive due to the possibility to complement the useful properties of both material systems. The photovoltaic devices that we study in this work consist of a p-i-n structure, which is also commonly used in inorganic solar cells. In such kind of structures, the light is mainly absorbed in the intrinsic silicon film and the p- and ntype films are used to create an electric field that separates electrons and holes to produce a photocurrent. In this work, we use an organic material (PEDOT:PSS) to replace the p-type inorganic film in amorphous silicon p-i-n structure. It is widely known, that PEDOT:PSS based organic film is highly transparent and its conductivity can be modified e.g. immerse in a solvent type. Here we present the results of experimental investigation of the effect of isopropanol (IPA) treatments in p-type (PEDOT:PSS) organic layer on characteristics of hybrid solar cell structure.
In this work, we present the results of investigation of thin film hybrid organic-inorganic photovoltaic structures based on flat heterojunction hydrogenated silicon (a-Si:H) and poly(3,4 ethylene dioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) fabricated on polyethylene naphthalate (PEN). Different thicknesses of transparent AL doped Zn:O (AZO) electrodes have been tested on PEN substrate and studied by atomic force microscopy (AFM). The AZO films on PEN substrate were statistically processed to obtain surface morphological characteristics, such as root mean square roughness RQ, skewness SK and kurtosis KU. Performance characteristics of fabricated photovoltaic structures have been measured and analyzed for different thicknesses of the transparent electrodes under standard illumination (AM 1.5 I0= 100mW/cm2). Structures on flexible substrates show reproducible performance characteristic as their glass substrate counterpart with values of JSC= 6 mA/cm2, VOC= 0.535 V, FF= 43 % and PCE= 1.41%.
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