Synthesis of water soluble MoS2 quantum dots from the monolayer nanosheets of MoS2, using thioglycolic acid (TGA) was reported in this study. TGA molecules not only exfoliated the bulk of MoS2, but also modified the hydrophobic surface of MoS2 with hydrophilic carboxylic acid groups.

We synthesized a series of polythiophenes (PTs) featuring 2-ethylhexyl-substituted terthiophene (T) or quaterthiophene (BT) as the conjugated unit in the polymer backbone with pendant conjugated tertbutyl-substituted triphenylamine (tTPA)-or carbazole (tCz)-containing moieties as side chains, namely PTtTPA, PBTtTPA, PTtCz and PBTtCz. Incorporating T and BT moieties into the polymer backbone and attaching tTPA or tCz units promoted efficient conjugation within the extended conjugated frameworks of the polymers, resulting in lower band-gap energies and red-shifting of the maximal UVVis absorption wavelength. The higher electron-donating ability of tTPA resulted in broader absorption bands and lower band-gap energies of PTtTPA and PBTtTPA as compared with PTtCz and PBTtCz. Incorporation of the T and BT moieties into the polymer backbone enhanced the compatibility of PT and the fullerene derivative by reducing the side-chain density of PT, thus providing sufficient free volume for efficient incorporation of [6,6]phenyl-C 61 -butyric acid methyl ester (PC 61 BM) into the polymer chains. Polymer solar cells (PSCs) were fabricated by spin-coating a blend of each PT with the fullerene derivative (PC 61 BM) as a composite film-type photoactive layer; PBTtTPA/PC 61 BM-based PSCs showed superior photovoltaic (PV) performance to PTtTPA/ PC 61 BM-based PSCs in terms of conjugation and absorption band broadness. However, PBTtCz/ PC 61 BM-based PSCs showed inferior PV performance to PTtCz/PC 61 BM-based PSCs. The lower HOMO level led to a higher open-circuit voltage (V oc ; 0.74 V) and larger photo-energy conversion efficiency (h; 2.77%) of PTtCz/PC 61 BM-based PSCs.

Polythiophene (PT) is one of the widely used donor materials for solution-processable polymer solar cells (PSCs). Much progress in PT-based PSCs can be attributed to the design of novel PTs exhibiting intense and broad visible absorption with high charge carrier mobility to increase short-circuit current density (Jsc), along with low-lying highest occupied molecular orbital (HOMO) levels to achieve large open circuit voltage (Voc) values. A promising strategy to tailor the photophysical properties and energy levels via covalently attaching electron donor and acceptor pendants on PTs backbone has attracted much attention recently. The geometry, electron-donating capacity, and composition of conjugated pendants are supposed to be the crucial factors in adjusting the conformation, energy levels, and photovoltaic performance of PTs. This review will go over the most recent approaches that enable researchers to obtain in-depth information in the development of PTs comprising conjugated pendants for PSCs.

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