The increase in atmospheric carbon dioxide is linked to climate changes; hence there is an urgent need to reduce the accumulation of CO₂ in the atmosphere. The utilization of CO₂ as a raw material in the synthesis of chemicals and liquid energy carriers offers a way to mitigate the increasing CO₂ buildup. This review covers six important CO₂ transformations namely: chemical transformations, photochemical reductions, chemical and electrochemical reductions, biological conversions, reforming and inorganic transformations. Furthermore, the vast research area of carbon capture and storage is reviewed briefly. This review is intended as an introduction to CO₂, its synthetic reactions and their possible role in future CO₂ mitigation schemes that has to match the scale of man-made CO₂ in the atmosphere, which rapidly approaches 1 teraton.

An inverted polymer solar cell geometry comprising a total of five layers was optimized using laboratory scale cells and the operational stability was studied under model atmospheres. The device geometry was substrate-ITO-ZnO-(active layer)-PEDOT:PSS-silver with P3HT-PCBM as the active layer. The inverted devices were compared to model devices with a normal geometry where the order of the layers was substrate-ITO-PEDOT:PSS-(active layer)-aluminium. In both cases illumination was through the substrate which requires that it is transparent. Both device types were optimized to a power conversion efficiency of 2.7% (1000 W m⁻², AM1.5G, 72 ± 2 °C). The devices were operated under illumination while being subjected to different atmospheres to identify the dominant modes of degradation. Dry nitrogen (99.999%), dry oxygen (99.5%), humid nitrogen (90 ± 5% relative humidity) and ambient atmosphere (20% oxygen, 20 ± 5% relative humidity) were employed and both device types were found to be stable in a nitrogen atmosphere during the test period of 200 hours. The devices with a normal geometry where an aluminium electrode is employed gave stable operation in dry oxygen but did not give stable device operation in the presence of humidity. The inverted devices behaved oppositely where the less reactive silver electrode gave stable operation in the presence of humidity but poor stability in the presence of oxygen. The inverted model device was then used to develop a new process giving access to fully roll-to-roll (R2R) processed polymer solar cells entirely by solution processing starting from a polyethyleneterephthalate (PET) substrate with a layer of indium-tin-oxide (ITO). All processing was performed in air without vacuum coating steps and modules comprising eight serially connected cells gave power conversion efficiencies as high as 2.1% for the full module with 120 cm² active area (AM1.5G, 393 W m⁻²) and up to 2.3% for modules with 4.8 cm² active area (AM1.5G, 1000 W m⁻²).