This review summarizes investigations carried out at the Laboratory of Photochemistry and Energy Conversion (LFCE) in the University of São Paulo dealing with design and characterization of ruthenium(II), rhenium(I) and iridium(III) polypyridine complexes with desired photochemical and photophysical properties in light of the development of optoelectronics and photoinduced energy conversion systems. First, the breakthroughs on molecular engineering of emissive ReI, RuII and IrIII complexes for the development of highly efficient light-emitting devices, such as organic light-emitting diodes (OLEDs) and light-emitting electrochemical cells (LECs), are presented. Then, the photochemical and photophysical properties of fac-[Re(CO)3(NN)(trans-L)]+ complexes (NN = bidentate polypyridyl ligands and trans-L = stilbene-like ligand), which find use in molecular machines and photosensors, are discussed. Finally, dye-sensitized energy conversion devices based on RuII complexes and natural dyes, such as dye-sensitized solar cells (DSCs) and dye-sensitized photoelectrosynthesis cells (DSPECs), are reviewed, highlighting some strategies for photoanode engineering aiming at improved device efficiencies.

The present work reports the use of anthocyanins extracted from mulberry (Morus Alba L.), raspberry (Rubus Idaeus L.) and blueberry (Vaccinium myrtillus L.) as sensitizers in dye-sensitized solar cells. The conversion efficiency of these devices is dependent on the extracts employed and can be rationalized in terms of their composition and spectral properties. Solar cells sensitized by the mulberry extract showed the highest efficiency among the fruits investigated. Moreover, a 16 cm² active area solar cell with the mulberry extract has presented fair good efficiency of conversion for natural dye-based solar cells, besides stability over twenty weeks, showing perspectives for developing these low cost devices with a commercial viability.

O extrato de Jambolão, Eugenia jambolana Lam, foi utilizado como um sensibilizador natural de um semicondutor com separação grande de bandas (TiO2) nas células solares fotoeletroquímica. O corante natural, adsorvido na superfície do semicondutor, absorve luz visível e promove transferência eletrônica na interface corante/semicondutor. A corrente e o potencial fotogerados tão altos como 2,3 mA e 711 mV, respectivamente, foram obtidos observando-se conversão eficiente de luz visível em eletricidade. O uso de um produto natural como o sensibilizador de semicondutor possibilita uma produção mais rápida e simples de células solares mais baratas que não agridem o meio ambiente.

The extract of Jambolão (java plum), Eugenia jambolana Lam, was used as a natural sensitizer of a wide band-gap semiconductor (TiO2) in photoelectrochemical solar cells. The natural dye, adsorbed onto the semiconductor surface, absorbs visible light and promotes electron transfer across the dye/semiconductor interface. Photogenerated current and voltage as high as 2.3 mA and 711 mV, respectively, were obtained and effective conversion of visible light into electricity was achieved. The use of a natural product as the semiconductor sensitizer enables a faster and simpler production of cheaper and environmentally friendly solar cells.