We present experimental demonstration of power generation obtained un­der ambient conditions at solar noon (see Methods section for details) of two types of cells. 1) CNT-only cells: cells are built with identical geom­etry but different CNT film compositions and thickness. This highlights how film composition affects cell performance (figure 2a). 2) Optimized cells: cells are built with the same CNT film thickness and composition, but with differences in construction techniques to isolate its role in cell efficiency (figure 2b-d).