Fig. 3

a Absorption spectra in the active layer (solid) for Device A (a) and Device B (b) with respect to that of the planar control (dashed). Spectra of relative absorption change for Device A (c) and Device B (d). Five enhancement peaks are labeled in c with λ _1A = 830 nm, λ _2A = 724 nm, λ _3A = 470 nm, λ _4A = 440 nm, and λ _5A = 416 nm, and the other five are labeled in d with λ _1B = 832 nm, λ _2B = 720 nm, λ _3B = 510 nm, λ _4B = 498 nm, and λ _5B = 468 nm. Device A and Device B are the devices yielding the optimal η _I in Fig. 2