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Photoelectrochemical growth of Se–Tefilms spontaneously produces highly ordered, nanoscale lamellar morphologieswith periodicities that can be tuned by varying the illumination wavelengthduring deposition. This phenomenon has been characterized furtherherein by determining the morphologies of photoelectrodeposited Se–Tefilms in response to tailored spectral illumination profiles. Se–Tefilms grown under illumination from four different sources, havingsimilar average wavelengths but having spectral bandwidths that spannedseveral orders of magnitude, all nevertheless produced similar structureswhich had a single, common periodicity as quantitatively identifiedvia Fourier analysis. Film deposition using simultaneous illuminationfrom two narrowband sources, which differed in average wavelengthby several hundred nanometers, resulted in a structure with only asingle periodicity intermediate between the periods observed wheneither source alone was used. This single periodicity could be variedby manipulating the relative intensity of the two sources. An iterativemodel that combined full-wave electromagnetic effects with Monte Carlogrowth simulations, and that considered only the fundamental light-materialinteractions during deposition, was in accord with the morphologiesobserved experimentally. Simulations of light absorption and concentrationin idealized lamellar arrays, in conjunction with all of the availabledata, additionally indicated that a self-optimization of the periodicityof the nanoscale pattern, resulting in the maximization of the anisotropyof interfacial light absorption in the three-dimensional structure,is consistent with the observed growth process of such films. [ABSTRACT FROM AUTHOR]