Diego Cortizo-Lacalle

BODIPY-based conjugated polymers for broadband light sensing and harvesting applications

The synthesis of novel low band-gap polymers has significantly improved light sensing and harvesting in polymer–fullerene devices. Here the synthesis of two low band-gap polymers based on the 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene core (BODIPY), and either bis(3,4-ethylenedioxythiophene) (bis-EDOT) or its all-sulfur analogue bis(3,4-ethylenedithiathiophene) (bis-EDTT) are described. The polymers demonstrate ambipolar charge transport and are shown to be suitable for broadband light sensing and solar energy harvesting in solution-processable polymer–fullerene devices.

Star-shaped fluorene–BODIPY oligomers: versatile donor–acceptor systems for luminescent solar concentrators

Luminescent solar concentrators (LSCs) are waveguides doped with luminescent centers that can spectrally and spatially concentrate sunlight. They can reduce the cost of photovoltaic energy production and are attractive prospects for photobioreactors and building-integrated applications. Reabsorption, caused by non-zero overlap between the absorption and emission spectra of the light-emitting centers, often limits LSC efficiency. Donor–acceptor energy-transfer complexes are one method to mitigate reabsorption by shifting the emission away from the main absorption peak. Here we introduce versatile star-shaped donor–acceptor molecules based on a central BODIPY energy acceptor with oligofluorene donor side units. Varying the oligofluorene chain length alters the relative oscillator strengths of the donor and acceptor, changing the severity of reabsorption for a given donor density, but also changing the luminescence yield and emission spectrum. We performed comprehensive device measurements and Monte Carlo ray tracing simulations of LSCs containing three oligofluorene–BODIPY donor–acceptor systems with different oligofluorene chain lengths, and then extended the simulation to study hypothetical analogs with higher donor–acceptor ratios and different terminal acceptors. We found that the measured structures permit waveguide propagation lengths on a par with state-of-the-art nanocrystalline emitters, while the proposed structures are viable candidates for photobioreactor and energy production roles and should be synthesized.

Solution processable diketopyrrolopyrrole (DPP) cored small molecules with BODIPY end groups as novel donors for organic solar cells

Summary Two novel triads based on a diketopyrrolopyrrole (DPP) central core and two 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) units attached by thiophene rings have been synthesised having high molar extinction coefficients. These triads were characterised and used as donor materials in small molecule, solution processable organic solar cells. Both triads were blended with PC71BM as an acceptor in different ratios by wt % and their photovoltaic properties were studied. For both the triads a modest photovoltaic performance was observed, having an efficiency of 0.65%. Moreover, in order to understand the ground and excited state properties and vertical absorption profile of DPP and BODIPY units within the triads, theoretical DFT and TDDFT calculations were performed.

An Air-Stable DPP-thieno-TTF Copolymer for Single-Material Solar Cell Devices and Field Effect Transistors

Following an approach developed in our group to incorporate tetrathiafulvalene (TTF) units into conjugated polymeric systems, we have studied a low band gap polymer incorporating TTF as a donor component. This polymer is based on a fused thieno-TTF unit that enables the direct incorporation of the TTF unit into the polymer, and a second comonomer based on the diketopyrrolopyrrole (DPP) molecule. These units represent a donor-acceptor copolymer system, p(DPP-TTF), showing strong absorption in the UV-visible region of the spectrum. An optimized p(DPP-TTF) polymer organic field effect transistor and a single material organic solar cell device showed excellent performance with a hole mobility of up to 5.3 × 10(-2) cm(2)/(V s) and a power conversion efficiency (PCE) of 0.3%, respectively. Bulk heterojunction organic photovoltaic devices of p(DPP-TTF) blended with phenyl-C71-butyric acid methyl ester (PC71BM) exhibited a PCE of 1.8%.

Synthesis and properties of novel star-shaped oligofluorene conjugated systems with BODIPY cores

Summary Star-shaped conjugated systems with varying oligofluorene arm length and substitution patterns of the central BODIPY core have been synthesised, leading to two families of compounds, T-B1–T-B4 and Y-B1–Y-B4, with T- and Y-shaped motifs, respectively. Thermal stability, cyclic voltammetry, absorption and photoluminescence spectroscopy of each member of these two families were studied in order to determine their suitability as emissive materials in photonic applications.

BODIPY star-shaped molecules as solid state colour converters for visible light communications

In this paper, we study a family of solid-state, organic semiconductors for visible light communications. The star-shaped molecules have a boron-dipyrromethene (BODIPY) core with a range of side arm lengths which control the photophysical properties. The molecules emit red light with photoluminescence quantum yields ranging from 22% to 56%. Thin films of the most promising BODIPY molecules were used as a red colour converter for visible light communications. The film enabled colour conversion with a modulation bandwidth of 73 MHz, which is 16 times higher than that of a typical phosphor used in LED lighting systems. A data rate of 370 Mbit/s was demonstrated using On-Off keying modulation in a free space link with a distance of ∼15 cm.

CHAPTER 11.2:Chalcogen‐Rich Compounds as Electron Donors

The search for new organic electron‐donor and electron‐acceptor materials has attracted enormous interest since the early 1970s. Since then, a vast number of different families of compounds have been developed and undoubtedly, among the electron donors, sulfur‐containing molecules represent an important series of compounds (e.g. derivatives of TTF and thiophene). In some cases, the larger chalcogen atoms, selenium and tellurium, have also been incorporated into the structures by substituting the sulfur atoms partially or completely to obtain more extensive intermolecular interactions and improved charge transport properties. In this chapter, we focus on the presentation of the main series of chalcogen‐rich electron donors and, when suitable, on a critical comparison of the properties of these materials by substitution with different chalcogen atoms. In the second edition of this chapter, we have incorporated the most relevant literature since the publication of the first edition, as well as a wider perspective of the application of these chalcogen‐rich compounds as electron donors