We report in this work efficient, fully printed tandem organic solar cells (OSCs) using solution-processed silver as the reflective bottom electrode and silver nanowires as the transparent top electrode. Employing two different band-gap photoactive materials with complementary absorption, the tandem OSCs are fully printed under ambient conditions without the use of indium tin oxide and vacuum-based deposition. The fully printed tandem devices achieve power conversion efficiencies of 5.81% (on glass) and 4.85% (on flexible substrate) without open circuit voltage (V_oc) losses. These results represent an important progress towards the realization of low-cost tandem OSCs by demonstrating the possibility of printing efficient organic tandem devices under ambient conditions onto production relevant carrier substrates.

The multi-junction concept is the most relevant approach to overcome the Shockley–Queisser limit for single-junction photovoltaic cells. The record efficiencies of several types of solar technologies are held by series-connected tandem configurations. However, the stringent current-matching criterion presents primarily a material challenge and permanently requires developing and processing novel semiconductors with desired bandgaps and thicknesses. Here we report a generic concept to alleviate this limitation. By integrating series- and parallel-interconnections into a triple-junction configuration, we find significantly relaxed material selection and current-matching constraints. To illustrate the versatile applicability of the proposed triple-junction concept, organic and organic-inorganic hybrid triple-junction solar cells are constructed by printing methods. High fill factors up to 68% without resistive losses are achieved for both organic and hybrid triple-junction devices. Series/parallel triple-junction cells with organic, as well as perovskite-based subcells may become a key technology to further advance the efficiency roadmap of the existing photovoltaic technologies.

Geopolymeric binders (GB) were produced using fly ash (FA) and electric arc furnace slag (EAFS). The slag has been added in the range of 0–40%. The effects of slag content on the strength, microstructure and thermal resistance were evaluated. It was found that the amount of EAFS up to 30% positively affects the strength evolution of GB. The main reaction product of FA/EAFS blends was amorphous N–(C)–A–S–H gel along with geopolymer-type gel (N–A–S–H). Thermal resistance of GB was considered from the standpoint of their mechanical and dimensional stability after heating in the temperature interval of 600–800 °C. The changes in mechanical and thermal properties of GB after heating are attributed to the changes in their structure. The results have shown that EAFS negatively affects the thermal resistance of GB above 600 °C due to the phase transition and morphological transformation of the amorphous gel phase