The cover picture shows a new polythiophene derivative PHTDFT designed for polymer solar cells. The introduction of fluorine atoms to the polymer backbones simultaneously lowers the HOMO energy level and narrows the bandgap. Benefiting from the lower HOMO, PHTDFT:PC₆₁BM (1:1) polymer solar cells obtain a power conversion efficiency of 1.11% and an impressed open-circuit voltage of 0.79 V under solar illumination AM1.5 (100 mW/cm²). More details are discussed in the article by Zhang et al. on page 1385–1390.

A series of donor-acceptor oligomer OBTTh_n (n=1–7) and polymer PBTTh₁ and PBTTh₂ composed of alternative 2,1,3-benzothiadiazole and 3-hexylthiophene have been designed and synthesized. The different orientation pattern of the side hexyl chains endows the polymers different regioregularity. It was found that the chain length of the oligomers and polymers has great impact on their photophysical, electrochemical and photovoltaic properties. Whereas, the side-chain regioregularity has less influence on their basic physical properties and photovoltaic performance.

By adding suitable amounts of SiNCs into MEH-PPV:PCBM blend, the device performance such as external quantum efficiency, short circuit current density and power conversion efficiency improved.

Two new polythiophene derivatives incorporating with 3,4-difluorothiphene units, PHTDFT and PDHOTDFT, show lower HOMO and narrower bandgap than that of P3HT. Benefiting from the lower HOMO, PHTDFT:PC₆₁BM (1:1) polymer solar cells obtain a power conversion efficiency of 1.11% and an impressed open-circuit voltage of 0.79 V under solar illumination AM1.5 (100 mW/cm²).

Isothianaphthene derivatives have been brominated successfully, which could be used directly as bulilding block in Stille couplings towards the application in organic electronics. A planar copolymer with the trans-ethene was synthesized which shows broad absorption with edge to 967 nm in film.

A series of organic conjugated molecules containing 2,3-benzopyridiazine as electron-withdrawing core and thiophene derivatives as electron-donating arms have been synthesized successfully. The optical properties and electrochemical behaviors of these molecules can be fine-tuned through changing the position of alkyl chains in the thiophene rings.

The concept of introducing π-conjugated but anti-aromatic repeating units into conjugated polymers has been explored. The thermal stability, optical and electrochemical properties of dithieno[a,e]pentalenes (DTP) based polymers have been characterized. The effect of introducing electron withdrawing repeating units into DTP based polymer on the physical properties of polymer has also been investigated. The new polymers showed broad absorption in visible and near-infrared region.

Three conjugated polymers based on ladder-type diindenopyrazine were synthesized for photovoltaic applications. The resulting solar cells using these polymers as donor materials showed a high open-circuit voltage of 1.00 V with a power conversion efficiency of 2.53%.

Efficient polymer solar cells from regioregular poly(3-hexylthiophene) (P3HT):fullerene derivative [6,6]-phenyl-C₆₁ butyric acid methyl ester (PC₆₁BM) mixtures were demonstrated, in which solution-processed vanadium oxide (VOx) was used as a hole-extracting layer (HEL).

A series of acceptor-donor-acceptor alternative small molecules (SMs) were synthesized containing electron-donating central building moieties of phenothiazine, 2,7-carbazole and thieno[3,4-b]thiophene and electron-accepting moieties of tetrazine on both sides.

Solvent mixtures (a solvent with higher volatility, higher surface energy and lower viscosity, with another solvent with lower volatility, lower surface energy and higher viscosity) were used to improve thickness uniformity of inkjet printed polymer films. More flat films were obtained instead of films with concave-lens like cross-section. Combination of intense Marangoni flow at early drying process and weak complementary flow at the later drying process was used to explain this improvement. Array of pixels with higher effective light-emitting area proportion was obtained.

Two novel donor-acceptor copolymers PDTSTT and PDTSDTTT containing dithienosilole and ketone modified thieno[3,4-b]thiophene are synthesized for the polymer solar cells. The two copolymers have broad absorption bands and low-lying HOMO energy levels. The insertion of thiophene bridges in PDTSDTTT can well relieve the steric hindrance between two units to induce a more compact packing and more favorable morphology. Without any treatment, the PDTSDTTT exhibits efficiency of 1% and relatively high open-circuit voltage of 0.75 V with blending PC₆₁BM in a typical bulk heterojunction.