Nanostructured Channel for Improving Emission Efficiency of Hybrid Light-Emitting Field-Effect Transistors.

We report on the mechanism of enhancing the luminance and external quantum efficiency (EQE) by developing nanostructured channels in hybrid (organic/inorganic) light-emitting transistors (HLETs) that combine a solution-processed oxide and a polymer heterostructure. The heterostructure comprised two parts: (i) the zinc tin oxide/zinc oxide (ZTO/ZnO), with and without ZnO nanowires (NWs) grown on the top of the ZTO/ZnO stack, as the charge transport layer and (ii) a polymer Super Yellow (SY, also known as PDY-132) layer as the light-emitting layer. Device characterization shows that using NWs significantly improves luminance and EQE (≈1.

Traps and transport resistance are the next frontiers for stable non-fullerene acceptor solar cells.

Stability is one of the most important challenges facing material research for organic solar cells (OSC) on their path to further commercialization. In the high-performance material system PM6:Y6 studied here, we investigate degradation mechanisms of inverted photovoltaic devices. We have identified two distinct degradation pathways: one requires the presence of both illumination and oxygen and features a short-circuit current reduction, the other one is induced thermally and marked by severe losses of open-circuit voltage and fill factor.

Single-junction organic solar cells with over 19% efficiency enabled by a refined double-fibril network morphology.

In organic photovoltaics, morphological control of donor and acceptor domains on the nanoscale is the key for enabling efficient exciton diffusion and dissociation, carrier transport and suppression of recombination losses. To realize this, here, we demonstrated a double-fibril network based on a ternary donor-acceptor morphology with multi-length scales constructed by combining ancillary conjugated polymer crystallizers and a non-fullerene acceptor filament assembly. Using this approach, we achieved an average power conversion efficiency of 19.

Using Ligand Engineering to Produce Efficient and Stable Pb-Sn Perovskite Solar Cells with Antioxidative 2D Capping Layers.

Pb-Sn binary halide perovskites are a promising photovoltaic material due to their low toxicity and optical absorption spectrum well matched to the solar spectrum. However, the ready oxidation of Sn to Sn makes the material system currently too unstable to commercialize. Herein, ligand engineering based on antioxidative tyramine (hydrochloride, TACl) is presented for the first time to increase the stability of this material system.

Molecular Doping Inhibits Charge Trapping in Low-Temperature-Processed ZnO toward Flexible Organic Solar Cells.

There has been a growing interest in the development of efficient flexible organic solar cells (OSCs) due to their unique capacity to provide energy sources for flexible electronics. To this end, it is required to design a compatible interlayer with low processing temperature and high electronic quality. In this work, we present that the electronic quality of the ZnO interlayer fabricated from a low-temperature (130 °C) sol-gel method can be significantly improved by doping an organic small molecule, TPT-S.

Self-Assembly of Chiral-at-End Diketopyrrolopyrroles: Symmetry Dependent Solution and Film Optical Activity and Photovoltaic Performance.

Chiral thiophene-diketopyrrolopyrrole derivatives have been synthesised to investigate the potential of stereochemistry and symmetry as a means of modulating properties by influencing self-assembly of these purely organic materials. In particular, derivatives of diketopyrrolopyrrole were employed because of their proven interest as dyes, especially for organic solar cells. The natural product myrtenal was used as the source of stereochemistry, introduced through a Kröhnke reaction of a thiophene-bearing pyridinium salt and diketopyrrolopyrroles were prepared through Suzuki coupling with this chiral moiety at one end only as well as at both ends.

Increasing organic solar cell efficiency with polymer interlayers.

We demonstrate how organic solar cell efficiency can be increased by introducing a pure polymer interlayer between the PEDOT:PSS layer and the polymer:fullerene blend. We observe an increase in device efficiency with three different material systems over a number of devices. Using both electrical characterization and numerical modeling we show that the increase in efficiency is caused by optical absorption in the pure polymer layer and hence efficient charge separation at the polymer bulkheterojunction interface.

A numerical study of mobility in thin films of fullerene derivatives.

The effect of functional group size on the electron mobility in films of fullerene derivatives is investigated numerically. A series of four C(60) derivatives are formed by attaching saturated hydrocarbon chains to the C(60) cage via a methano bridge. For each of the derivatives investigated, molecular dynamics is used to generate a realistic material morphology.