Electrodeposition of inorganic compound thin films in the presence of certain organic molecules results in self‐assembly of various hybrid thin films with new properties. Examples of new discoveries by the authors are reviewed, taking cathodic formation of a ZnO/dye hybrid as the leading example. Hybridization of eosinY leads to the formation of highly oriented porous crystalline ZnO as the consequence of dye loading. The hybrid formation is a highly complicated process involving complex chemistry of many molecular and ionic constituents. However, electrochemical analyses of the relevant phenomena indicate the possibility of reaching a comprehensive understanding of the mechanism, giving us the chance to further develop them into industrial technologies. The porous crystals are ideal for photoelectrodes in dye‐sensitized solar cells. As the process also permits the use of non‐heat‐resistant substrates, the technology can be applied for the development of colorful and light‐weight plastic solar cells.

Lead-free double perovskites have been proposed as promising nontoxic photovoltaic materials for the replacement of lead perovskites. While the latter ones reach remarkably high power conversion efficiencies (PCEs) above 23% in small lab devices, the lead-free double perovskites so far have severely underperformed, with PCEs below 3% for the prototypical system Cs 2 AgBiBr 6 , in spite of considerable optimization efforts by several groups. Here, we present a detailed study of Cs 2 AgBiBr 6 thin films deposited on poly(methyl methacrylate) and mesoporous TiO 2 . Femtosecond UV−vis−NIR transient absorption experiments clearly identify the presence of excitons. In addition, strong electron−phonon coupling via Froḧlich interactions is observed in terms of pronounced coherent oscillation of a strong A 1g optical phonon mode of the double perovskite at 177 cm −1 . Similar behavior is also found for the related vacancy-ordered perovskite Cs 3 Bi 2 Br 9 and the parent compound BiBr 3 . Excitonic effects and electron−phonon coupling are known to induce unwanted electron−hole recombination and hamper carrier transport. New strategies will thus be required for efficient carrier extraction at the interfaces of the double perovskite with electron and hole transport layers.

Cathodic electrodeposition in an aqueous mixed solution of zinc nitrate and water-soluble tetrasulfonated metallophthalocyanines (TSPcMs), in which M ) Zn(II) (TSPcZn), Al(III)-[OH] (TSPcAl), or Si(IV)[OH] 2 (TSPcSi), resulted in a self-assembled growth of zinc oxide (ZnO) thin films whose surface is modified by TSPcMs. It has been found that the adsorption of TSPcM onto the growing surface of ZnO strongly affects the crystal growth and the orientation of the ZnO crystallites. The effect was most prominently seen with TSPcSi, creating a film looking like stacking disks aligned perpendicular to the substrate. Crystallographic studies by X-ray diffraction and TEM observation coupled with the selected area electron beam diffraction have revealed that thin platelike crystals, whose planes and edges correspond to the (002) and (100) crystal faces, respectively, are aligned in the same orientation around the c-axis within the stacks. The evolution of this unique structure is interpreted as arising from the preferential adsorption of TSPcMs at the (002) planes, leading to film growth preferentially in the (100) direction. Optical analysis of the films also revealed high order in the interactions among TSPcMs. Because of the strong intermolecular attraction, TSPcZn forms multilayers of π-stacking aggregates on ZnO as confirmed by the characteristic blueshift of the Q-band absorption. Thus, TSPcZn could be condensed at a very high concentration exceeding 1 M in the deposited film. These surface aggregates were completely removed by dipping the film in a solution of cationic detergent, cetyltrimethylammonium chloride, while only leaving surface-bound monomeric TSPcZn. By contrast, the aggregation was hindered for TSPcAl and TSPcSi because of the presence of axially coordinated OH -, and monomeric adsorption was found in the electrodeposited films.

The photoactive materials in dye‐sensitized solar cells (DSSCs) are conventionally produced by colloid coating and heat treatment followed by dye adsorption by dipping in solution. One disadvantage of this procedure is that only heat‐resistant materials can be used. Here the one‐step self‐assembly of ZnO/eosin Y thin films is reported. It is shown that a large proportion of the incorporated eosin Y dye molecules act as sensitizers, making the films suitable as sensitized photoelectrodes in DSSCs. No heat treatment is required, allowing non‐heat‐resistant substrates such as flexible conductive plastic films to be used.