Knowledge of absolute absorbance coefficients is important when designing materials for light harvesting (including semiconductors for photovoltaic and photoelectrolysis applications) or for light absorption (pigments and dyes). Furthermore, knowledge about absolute absorbances is also very important when assigning the type and origin of observed optical transitions. In the absence of this knowledge, errors are frequently made in the assignment of transitions. Unfortunately, the widely used diffuse reflectance methods for studying powder samples (measurements made using an integrating sphere followed by a Kubelka-Munk transform) only provide information about relative and not absolute absorbance. We have recently developed novel self-referenced methods for simply determining the refractive index, n(E), for loose powder samples. When combined with information about particle size, absolute absorption coefficients, α(E), can be determined. These new methods will be discussed in the context of validation studies and their application to study systems of interest for solar water splitting, where they have been used to provide the first-ever measure of absolute absorbances in some complex chemical systems that can only readily be prepared as powders.

New methods for measuring absolute optical constants using loose powders: Implementation, validation, and renewable energy applications

2019 Fall National Meeting

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