Figure 12. (a) Optical micrographs of PCE11:PCBM films captured during various isothermal annealing steps at temperatures of 140, 125, 110, and 80 °C. Reproduced from [136]. TEM images (b) and fluorescence spectra (c) of the blend film were processed at different temperatures. Reproduced from [112]. (d) Changes in the fluorescence intensity of blend films at 620 and 725 nm when subjected to various temperatures. Reproduced from [112].