Intrinsic Detectivity Limits of Organic Near-Infrared Photodetectors

Organic photodetectors (OPDs) with a performance comparable to that of conventional inorganic ones have recently been demonstrated for the visible regime. However, near-infrared photodetection has proven to be challenging and, to date, the true potential of organic semiconductors in this spectral range (800-2500 nm) remains largely unexplored. In this work, it is shown that the main factor limiting the specific detectivity (D*) is non-radiative recombination, which is also known to be the main contributor to open-circuit voltage losses. The relation between open-circuit voltage, dark current, and noise current is demonstrated using four bulk-heterojunction devices based on narrow-gap donor polymers. Their maximum achievable D* is calculated alongside a large set of devices to demonstrate an intrinsic upper limit of D* as a function of the optical gap. It is concluded that OPDs have the potential to be a useful technology up to 2000 nm, given that high external quantum efficiencies can be maintained at these low photon energies.

The Impact of Acceptor-Acceptor Homocoupling on the Optoelectronic Properties and Photovoltaic Performance of PDTSQxff Low Bandgap Polymers

Push-pull-type conjugated polymers applied in organic electronics do not always contain a perfect alternation of donor and acceptor building blocks. Misscouplings can occur, which have a noticeable effect on the device performance. In this work, the influence of homocoupling on the optoelectronic properties and photovoltaic performance of PDTSQx_ff polymers is investigated, with a specific focus on the quinoxaline acceptor moieties. A homocoupled biquinoxaline segment is intentionally inserted in specific ratios during the polymerization. These homocoupled units cause a gradually blue-shifted absorption, while the highest occupied molecular orbital energy levels decrease only significantly upon the presence of 75-100% of homocouplings. Density functional theory calculations show that the homocoupled acceptor unit generates a twist in the polymer backbone, which leads to a decreased conjugation length and a reduced aggregation tendency. The virtually defect-free PDTSQx_ff affords a solar cell efficiency of 5.4%, which only decreases substantially upon incorporating a homocoupling degree over 50%.

Functionalization of boron-doped diamond with a push–pull chromophore via Sonogashira and CuAAC chemistry

Functionalization of boron-doped diamond with a push–pull chromophore via Sonogashira cross-coupling affords better photovoltaic performances as compared to functionalization via CuAAC.

Impact of structure and homo-coupling of the central donor unit of small molecule organic semiconductors on solar cell performance

Next to the molecular structure, homo-coupling of the central donor moiety has a profound influence on organic solar cell efficiency.

Continuous Flow Polymer Synthesis toward Reproducible Large-Scale Production for Efficient Bulk Heterojunction Organic Solar Cells

Organic photovoltaics (OPV) have attracted great interest as a solar cell technology with appealing mechanical, aesthetical, and economies-of-scale features. To drive OPV toward economic viability, low-cost, large-scale module production has to be realized in combination with increased top-quality material availability and minimal batch-to-batch variation. To this extent, continuous flow chemistry can serve as a powerful tool. In this contribution, a flow protocol is optimized for the high performance benzodithiophene-thienopyrroledione copolymer PBDTTPD and the material quality is probed through systematic solar-cell evaluation. A stepwise approach is adopted to turn the batch process into a reproducible and scalable continuous flow procedure. Solar cell devices fabricated using the obtained polymer batches deliver an average power conversion efficiency of 7.2 %. Upon incorporation of an ionic polythiophene-based cathodic interlayer, the photovoltaic performance could be enhanced to a maximum efficiency of 9.1 %.

Branched and linear A2–D–A1–D–A2isoindigo-based solution-processable small molecules for organic field-effect transistors and solar cells

A₂–D–A₁–D–A₂type small molecules were synthesized, providing a solar cell efficiency of 1.9% and hole mobility of 3.7 × 10⁻³cm²V⁻¹s⁻¹.

Synthesis of a multifunctional poly(p-phenylene ethynylene) scaffold with clickable azide-containing side chains for (bio)sensor applications

Clickable poly(p-phenylene ethynylene) (PPE) copolymers were designed and synthesized towards (bio)sensor applications.

Dye-sensitization of boron-doped diamond foam: champion photoelectrochemical performance of diamond electrodes under solar light illumination

Diamond foams composed of hollow spheres of polycrystalline boron-doped diamond are chemically modified with two donor–acceptor type molecular dyes, BT-Rho and CPDT-Fur, and tested as electrode materials for p-type dye-sensitized solar cells.