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A ZnO/Cu2O-based combinatorial heterojunction device library was successfully fabricated by a simple spray pyrolysis technique using ITO-coated glass as the substrate. The combinatorial approach was introduced to analyze the impact of the ZnO and Cu2O layer thicknesses on the performance of the solar cells. The thickness of the ZnO layer was varied from ~50 to 320 nm, and the Cu2O layer was deposited orthogonal to the ZnO thickness gradient. In the case of Cu2O, the thickness varied from ~200 to 800 nm. The photovoltaic performance of the cells is strongly dependent on the absorber layer thickness for a particular window layer thickness and reaches a maximum short-circuit current density of 3.9 mA/cm² when the absorber layer thickness just crosses ~700 nm. Reducing the thicknesses of the active layers leads to a sharp decrease in the device performance. It is shown that the entire built-in bias of the heterojunction is created in the absorber layer due to low carrier density. The poor performance of the devices having lower thicknesses is attributed to different interfacial phenomena such as optical losses due to the thin Cu2O layer, back-contact recombination of the carriers due to the low layer thickness because a minimum heterojunction thickness is required for the formation of the full built-in bias that slows down the recombination of the carriers, and other factors. [ABSTRACT FROM AUTHOR]

An efficient mathematical strategy in the field of solution processed electrochromic (EC) films is outlined as a combination of an experimental work, modeling, and information extraction from massive computational data via statistical software. Design of Experiment (DOE) was used for statistical multivariate analysis and prediction of mixtures through a multiple regression model, as well as the optimization of a five-component sol--gel precursor subjected to complex constraints. This approach significantly reduces the number of experiments to be realized, from 162 in the full factorial (L = 3) and 72 in the extreme vertices (D = 2) approach down to only 30 runs, while still maintaining a high accuracy of the analysis. By carrying out a finite number of experiments, the empirical modeling in this study shows reasonably good prediction ability in terms of the overall EC performance. An optimized ink formulation was employed in a prototype of a passive EC matrix fabricated in order to test and trial this optically active material system together with a solid-state electrolyte for the prospective application in EC displays. Coupling of DOE with chromogenic material formulation shows the potential to maximize the capabilities of these systems and ensures increased productivity in many potential solution-processed electrochemical applications. [ABSTRACT FROM AUTHOR]