A series of thienopyrazine-based donor–acceptor–donor (D–A–D) near-infrared (NIR) fluorescent compounds were synthesized through a rapid, palladium-catalyzed C–H activation route. The dyes were studied through computational analysis, electrochemical properties analysis, and characterization of their photophysical properties. Large Stokes shifts of approximately 175 nm were observed, which led to near-infrared emission. Computational evaluation shows that the origin of this large Stokes shift is a significant molecular reorganization particularly about the D–A bond. The series exhibits quantum yields of up to φ = >4%, with emission maxima ranging from 725 to 820 nm. The emission is strong in solution, in thin films, and also in isolation at the single-molecule level. Their stable emission at the single-molecule level makes these compounds good candidates for single-molecule photon sources in the near-infrared.

A novel organic sensitizer (AP3) with dual donors and dual anchor-acceptors based on an electron deficient thieno [3,4-b]pyrazine (TPz) π-bridge was synthesized, which shows an impressively high J sc of 17.6 mA/cm 2 when cosensitized with D35 (12.4 mA/cm 2 as a single dye). Device power conversion efficiencies were observed at 7.5% under full sun intensity and in excess of 10% under reduced sun intensity. This novel dye design approach allows for devices showing photostability beyond 500 h for continuous irradiation and a tunable dye structure with an incident power conversion efficiency breadth reaching 800 nm from a simple-to-synthesize organic dye. Dye characterization with cyclic voltammetry, solution and film absorption, and computational analysis are all presented. Additionally, device characterization was performed through IV curves, IPCE, electron lifetime measurements, transient absorption spectroscopy, and current dynamic measurements at varying sun intensities to better understand the origin of the high device power conversion efficiencies as well as the interactions of AP3 and D35 in DSC devices.

A blue organic near infrared (NIR) absorbing sensitizer, AP25, is investigated for use in broadly absorbing dye-sensitized solar cells (DSCs).

The design of visible light absorbing organic dyes as strong photoinduced oxidants is needed for many potential applications in energy production and storage. To access more positive potentials, the electron deficient thienopyrroledione building block is promising as a π-bridge combined with weak aryl-ether donor groups and the phenyl-cyanoacetic acid acceptor group. The thienopyrroledione (TPD) building block is compared to the ubiquitous benzothiadiazole (BTD) building block, which was recently used in a dye-sensitized solar cell (DSC) device with >1.4 V photovoltage output. The variation in dye donor group is studied through UV−vis absorption spectroscopy and electrochemical methods both in solution and on TiO 2 films. The TPD building block resulted in a more positive ground state and excited state oxidation potential, a higher photocurrent (up to 3.5 mA/ cm 2 ), and a higher power conversion efficiency (up to 2.9%) than a BTD analogue while retaining comparable photovoltages (∼1.3 versus ∼1.4 V). Computational analysis was used to better understand the optical properties of the thienopyrroledionebased dyes showing overlap of orbitals at the TPD bridge in the S 0 and S 1 states. The dyes were analyzed in high voltage-DSC devices with a challenging to oxidize redox shuttle, Fe(bpy) 3 2+ , at 1.37 V versus NHE.

The thienopyrazine (TPz) building block allows for NIR photon absorption in dye-sensitized solar cells (DSCs) when used as a π-bridge. We synthesized and characterized 7 organic sensitizers employing thienopyrazine (TPz) as a π-bridge in a double donor, double acceptor organic dye design. Donor groups are varied based on electron donating strength and sterics at the donor-π bridge bond with the acceptor groups varied as either carboxylic acids or benzoic acids on the π-bridge. This dye design was found to be remarkably tunable with solution absorption onsets ranging from 750 to near 1000 nm. Interestingly, the solution absorption measurements do not accurately approximate the dye absorption on TiO films with up to a 250 nm blue-shift of the dye absorption onset on TiO. This shift in absorption and the effect on electron transfer properties is investigated via computational analysis, time-correlated single photon counting studies, and transient absorption spectroscopy. Structure-performance relationships were analyzed for the dyes in DSC devices with the highest performance observed at 17.6 mA/cm of photocurrent and 7.5% PCE for a cosensitized device with a panchromatic IPCE onset of 800 nm.