Solution-processed organic photovoltaic cells (OPVs) hold great promise to enable roll-to-roll printing of environmentally friendly, mechanically flexible and cost-effective photovoltaic devices. Nevertheless, many high-performing systems show best power conversion efficiencies (PCEs) with a thin active layer (thickness is ~100 nm) that is difficult to translate to roll-to-roll processing with high reproducibility. Here we report a new molecular donor, benzodithiophene terthiophene rhodanine (BTR), which exhibits good processability, nematic liquid crystalline behaviour and excellent optoelectronic properties. A maximum PCE of 9.3% is achieved under AM 1.5G solar irradiation, with fill factor reaching 77%, rarely achieved in solution-processed OPVs. Particularly promising is the fact that BTR-based devices with active layer thicknesses up to 400 nm can still afford high fill factor of ~70% and high PCE of ~8%. Together, the results suggest, with better device architectures for longer device lifetime, BTR is an ideal candidate for mass production of OPVs.

The evolution of electronic energy levels of controlled air and oxygen exposed molybdenum trioxide $\left({\text{MoO}}_3\right)$ films has been investigated with ultraviolet photoemission spectroscopy, inverse photoemission spectroscopy, and x-ray photoemission spectroscopy. We found that while most of the electronic levels of as deposited ${\text{MoO}}_3$ films remained largely intact, the reduction in the work function (WF) was substantial. The gradual surface WF change from 6.8 to 5.3 eV was observed for air exposed film, while oxygen exposed film the surface WF saturated at $\sim 5.7\text{eV}$ . Two distinct stages of exposure are observed, the first dominated by oxygen adsorption for $<{10}^{13}\text{Langmuir}$ (L) exposure and at the final step moisture absorption $>{10}^{13}\text{L}$ .