In terms of photophysical measurements, as long as the PC is sufficiently soluble in the solvent, a useful measurement can be taken; however, for electrochemical measurements that require a conductive solution, non-polar solvents are generally unsuitable. Gratifyingly, a survey of the photocatalysis literature indicates that polar aprotic solvents are most often used, particularly MeCN, DMSO and DMF. A library of these parameters would serve as a useful resource to aid in the decision making as to which PC should be used for a particular reaction class and substrate. Indeed, an accurate knowledge of the optoelectronic properties of the PC in concert with those of the substrate(s) are essential for an analysis of the thermodynamic driving force for a particular reaction. However, an assessment of the competing kinetics of both photophysical and photochemical processes are often neglected, as are the solubility and the stability of reaction intermediates. To address this identified issue and given the complex influences the solvent can have on a photocatalytic reaction, we selected a series of eight versatile and commonly used PCs for optoelectronic characterization in four solvents of varying polarity, to understand how variation of the photophysical properties of the PC with solvent polarity can be correlated to photocatalytic performance. Although we recognise that solvent polarity will also influence the optoelectronic properties of the substrates in the photocatalysis reaction, as a first step we have focused exclusively on the PC in this study. We then evaluated the efficiency of some of these PCs in representative photocatalysis reactions, encompassing reactions across a range of these solvents proceeding via either PET or PEnT mechanisms, and attempted to correlate yields to the thermodynamic parameters of the PCs.