Moritz Riede

Abstract:

The present study discusses the thermoluminescence (TL) characteristics of monoclinic barium titanate (BaTi5O11) which is chemically prepared using the sol–gel technique. The crystallinity is confirmed by X-ray diffraction, and the oxidation state of each element, morphology, and particle size of the prepared powder are chemically probed by different spectroscopic tools including X-ray Photoelectron Spectroscopy and Energy dispersive X-Ray spectroscopy. The sample is irradiated by a beta (β)-source with different applied doses in the range of 1.1––385 Gy. The kinetic parameters which correspond to the charge carrier traps were determined. The analysis methods indicated that the TL glow curve of BaTi5O11 consists of 6 overlapped peaks corresponding to 6 electron traps. The values for the trap depth are found to be in the range 0.94–1.40 eV and the TL glow peaks are located between 380.4 and 560.5 K. The study confirms the potential of BaTi5O11 for β-dosimetry.

Abstract:

<jats:p>The acceptor crystallinity has long been associated with favourable organic solar cells (OSCs) properties such as high mobility and Fill Factor. In particular, this applies to acceptor materials such as...</jats:p>

Abstract:

<jats:p>The record power conversion efficiency of solution-processed organic solar cells (OSCs) has almost doubled since non-fullerene acceptors (NFAs) replaced fullerene derivatives as the best-performing acceptor molecules. The successful transition from C60 to NFAs is still pending for vacuum-thermal evaporated (VTE) OSCs, not least because most NFAs are too large to be evaporated without breaking. Due to VTE’s relevance in terms of industrial manufacturing, discovering high-performing VTE NFAs is a major opportunity for OSCs. Here, we fabricate evaporated OSCs based on the NFA BTIC-H known from solution processing. This A–D–A molecule has an unfused bithiophene core, 1,1-dicyanomethylene-3-indanone end groups, and hexyl side chains, making it small enough to be evaporated well. We pair BTIC-H with four commonly used evaporated donors—DCV5T-Me(3,3), DTDCPB, HB194, and SubNc—in planar heterojunctions. We observe appreciable photocurrents and a voltage loss of ∼0.8 V, matching that of corresponding C60 devices. Donor:BTIC-H bulk heterojunctions likely face charge collection issues due to unfavorable microstructure. Our work demonstrates one of few NFA based evaporated OSCs with encouraging performance results and gives one potential starting point for molecule design of further NFAs suitable for VTE.</jats:p>

Abstract:

The advent of nonfullerene acceptors (NFAs) enabled records of organic photovoltaics (OPVs) exceeding 19% power conversion efficiency in the laboratory. However, high-efficiency NFAs have so far only been realized in solution-processed blends. Due to its proven track record in upscaled industrial production, vacuum thermal evaporation (VTE) is of prime interest for real-world OPV commercialization. Here, we combine the benchmark solution-processed NFA Y6 with three different evaporated donors in a bilayer (planar heterojunction) architecture. We find that voltage losses decrease by hundreds of millivolts when VTE donors are paired with the NFA instead of the fullerene C60, the current standard acceptor in VTE OPVs. By showing that evaporated small-molecule donors behave much like solution-processed donor polymers in terms of voltage loss when combined with NFAs, we highlight the immense potential for evaporable NFAs and the urgent need to direct synthesis efforts toward making smaller, evaporable compounds.