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Abstract In this study, we extend the dust-independent Hatzidimitriou relation between cluster age andd_B−Rcolor difference between the red giant branch (RGB) and red clump to younger cluster ages. We perform membership analysis on 14 galactic open clusters using Gaia DR3 astrometry, then compute the difference in color of the RGB and red clumpd_B−Rusing Gaia photometry. We also computed_B−Rfor five fields surrounding Small Magellanic Cloud clusters. We find that the trend derived from older clusters does not extrapolate to younger ages and becomes double valued. We confirm thatd_B−Ris independent of metallicity. Current stellar evolutionary isochrones do not quantitatively reproduce the trend and furthermore predict an increased color gap with a decrease in metallicity that is not echoed in the data. Integrated light models based on current isochrones exaggerate the color change over the ​​​​​​−0.5 < [Fe/H] < 0 interval at the few-percent level. 

Printable and flexible organic solar panels are promising sources of inexpensive, large-scale renewable energy, where panels can be manufactured by printing from polymer inks. There are some limitations to these types of solar cells, however. First, toxic halogenated solvents have historically been necessary to dissolve polymers to make the ink. In addition, organic solar cells typically have high rates of recombination, which limits their efficiency. Here, we use a transient photovoltage (TPV) technique to measure charge lifetimes in cells made from two different organic solvents. The first solvent is toxic, halogenated dichlorobenzene (DCB) which is typically used to make organic solar cells. The other is a less toxic, non-halogenated solvent, carbon disulfide (CS2). By varying the processing methods in this way, we find that cells made from CS2 have longer charge lifetimes and higher efficiencies than those made with DCB, as well as a different recombination rate order. Possible reasons for these differences are explored using simple analytic modeling. Our model indicates that while bimolecular recombination is dominant in both types of cells, those processed with DCB may have more trap-assisted recombination present than those processed with CS2. Overall, this work demonstrates that we may be able to decrease the toxicity of organic solar cell manufacturing and simultaneously improve the efficiency of the devices, bringing this powerful method of capturing solar energy to the forefront of sustainable energy solutions.