1,10-Phenanthroline entails several appealing structural and chemical properties: rigidity, planarity, aromaticity, basicity, chelating capability. This makes it a versatile starting material for synthetic organic, inorganic and supramolecular chemistry. In this tutorial review we examine how the chemical versatility of pristine 1,10-phenanthroline, a weakly fluorescent molecule, has been exploited to design many UV-Vis-NIR luminescent organic derivatives and coordination compounds with transition-metal (Ru(II), Os(II), Rh(III), Cr(III), Pt(II), Zn(II), Cu(I), Ag(I)) and rare-earth (Eu(III),Tb(III), Yb(III), Nd(III), Er(III)) cations. They are utilized for many analytical and technological applications.

Dye-sensitized solar cells (DSCs) have proven to be one of the best photovoltaic approaches for harnessing indoor/artificial light. Herein, we report two new molecularly engineered, cost-effective, metal-free, carbazole-based D–π–A sensitizers (YK 8 and YK 9) by judiciously varying their π-spacers, which are suitable for indoor photovoltaic applications. Using YK 8, we achieved an efficiency of 28.7% under standard 1000 lux Osram 14 W T2 cool day light fluorescent tube illumination with a power output of 68.88 μW cm⁻² and 30.24% with a power output of 108.85 μW cm⁻² under a higher illumination intensity of 1500 lux without co-sensitizers using iodide/triiodide electrolyte. With a small footprint/active area of 1.24 cm², we could power a temperature sensor completely autonomously at a low light intensity of 500 lux, displaying the potential of these indoor photovoltaic devices to serve as energy sources for low-power sensors and actuators on the Internet of Things (IoT) network, reducing the dependence on batteries and leading to a smaller carbon footprint. The role of the π-spacer and its influence on recombination and device performance were explored via extensive interfacial studies.