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Spiro-OMeTAD has become a ubiquitous hole-transporting material (HTM) in perovskite-based solar cells. However, it has several intrinsic drawbacks including its long-term stability, low conductivity and hole-mobility. Hence, the synthesis of new derivatives with improved charge transporting properties remains an important goal. Here, we have devised a novel synthetic route to prepare unsymmetrically functionalised Spiro-OMeTAD derivatives. We report the synthesis of a mono-demethylated Spiro-OMeTAD derivative, SOT-OH, utilising two different synthetic protocols and show two new derivatives, a dimer (SOT-D) and a trimer (SOT-T) as exemplars. We fully characterise the developed materials and show significantly higher conductivity values than Spiro-OMeTAD when doped with standard ionic salts at the same concentrations. The solar cells fabricated using the mixed composition Cs0.05(FA0.85MA0.15)0.95PbI3 perovskite and the novel SOT-D show power conversion efficiencies of up to 16.4% under standard AM1.5 illumination compared to 16.1% observed when using the benchmark Spiro-OMeTAD.

A new flavin-based gelator is reported which forms micellar structures at high pH and gels at low pH. This flavin can be used for the photooxidation of thiols under visible light, with the catalytic efficiency being linked to the self-assembled structures present.

Chiral biological and pharmaceutical molecules are analyzed with phenomena that monitor their very weak differential interaction with circularly polarized light. This inherent weakness results in detection levels for chiral molecules that are inferior, by at least six orders of magnitude, to the single molecule level achieved by state-of-the-art chirally insensitive spectroscopic measurements. Here, we show a phenomenon based on chiral quantum metamaterials (CQMs) that overcomes these intrinsic limits. Specifically, the emission from a quantum emitter, a semiconductor quantum dot (QD), selectively placed in a chiral nanocavity is strongly perturbed when individual biomolecules (here, antibodies) are introduced into the cavity. The effect is extremely sensitive, with six molecules per nanocavity being easily detected. The phenomenon is attributed to the CQM being responsive to significant local changes in the optical density of states caused by the introduction of the biomolecule into the cavity. These local changes in the metamaterial electromagnetic environment, and hence the biomolecules, are invisible to “classical” light-scattering-based measurements. Given the extremely large effects reported, our work presages next generation technologies for rapid hypersensitive measurements with applications in nanometrology and biodetection.

Organic hole-transporting materials (HTM) have shown excellent ability in achieving high efficiency perovskite solar cells. However, their high cost significantly limits their applications in scaling-up perovskite solar cells. Here, we report an efficient, low-cost HTM, called TAT-tBuSty, comprising a central triazatruxene moiety with 3 terminal tert-butoxy styrene groups and 3 hexyl side chains on the indole nitrogen. For the first time, we use an inexpensive liquid precur-sor to attach the donor ligand to the molecule. This enables purification of the HTM using a silica plug and recrystallization without the need for complicated column chromatography, which is typically required to purify solid-precursor-prepared HTMs. We estimate that the cost for the purified TAT-tBuSty is $69.90 g-1, which is 35% cheaper than the widely-used 2,2′7,7′-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9′-spirobifluorene (spiro-OMeTAD; ca. $112.05 g-1). Using this low-cost TAT-tBuSty as the HTM in a caesium-formamidinium mixed-cation perovskite solar cell, we have successfully achieved a champion power conversion efficiency (PCE) of 20.3% (19.4% stabilized efficiency), which is comparable to the efficiency of devices using the reference spiro-OMeTAD HTM. Our work is crucial for up-scaling of next-generation high-performance metal-halide perovskite solar cells.

Singlet exciton diffusion was studied in the efficient organic photovoltaic electron donor material DTS(FBTTh2)2 . Three complementary time-resolved fluorescence measurements were performed: quenching in planar heterojunctions with an electron acceptor; exciton-exciton annihilation; and fluorescence depolarization. The average exciton diffusivity increases upon annealing from 1.6 ×〖10〗^(-3) 〖cm〗^2 s^(-1) to 3.6 ×〖10〗^(-3) 〖cm〗^2 s^(-1), resulting in an enhancement of the mean two–dimensional exciton diffusion length (L_D=√4Dτ) from 15 nm to 27 nm. About 30% of the excitons get trapped very quickly in as-cast films and remain immobilized throughout their entire lifetime, whilst the remaining excitons diffuse with a similar rate to the excitons in the annealed films. The high exciton diffusion coefficient of the material leads to it being able to harvest excitons efficiently from large donor domains in bulk heterojunctions.

Organic compounds displaying second-order non-linear optical properties are key materials for optoelectronics. Here, three push-pull flavin derivates (FLA-A-C) have been synthesised and their optical, redox and second harmonic generation (SHG) properties have been investigated. In particular, we describe the role differing electron donor units (N, N-dimethylaniline-, N, N-diphenylaniline- and ferrocenyl-) attached through the C(8) position of the flavin unit have on the optical and redox properties of the latter. Hyper-Rayleigh scattering in dioxane solutions using a fundamental wavelength of 1064 nm was employed to evaluate their second-order nonlinear optical properties. Our experiments have indicated that their first hyperpolarisabilities (beta) are influenced by the electronic nature and strength of the donor groups. N, N-dimethylaniline-functionalised derivative FLA-A, exhibited the largest first hyperpolarisability (beta = 9550 x 10(-30) esu, using the T convention) and high decomposition temperature (T-d = 312 degrees C), thus indicating its potential application as a useful material for incorporation into non-linear optical devices., GC thanks EPSRC (EP/E036244/1). VR thanks the NSF (CHE-1307021). NM thanks the Ministry of Higher Education and Scientific Research of Iraq and the University of Kirkuk. MMR thanks the Funds provided by FCT through the Chemistry Research Centre of the University of Minho (Ref. UID/QUI/00686/2013 and UID/QUI/0686/2016) and a PhD grant to S. S. M. Fernandes (SFRH/BD/87786/2012). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network and was purchased within the framework of the National Program for Scientific Re-equipment, with funds from FCT., info:eu-repo/semantics/publishedVersion