A modular photochemical reactor system having a plurality of fluidic modules each having i) a central planar process fluid layer and ii) two outer planar thermal control fluid layers for containing flowing thermal control fluid and a plurality of illumination modules, the illumination modules of the plurality each having a planar form with first and second major surfaces and each having at least a first array of semiconductor emitters, the emitters positioned to emit from or through the first major surface, wherein the first array of semiconductor emitters has at least a first emitter and a second emitter, the first emitter capable of emitting at a first center wavelength and the second emitter capable of emitting at a second center wavelength, the first and second center wavelengths differing from each other.

A modular photochemical reactor system comprises a plurality of fluidic modules (20) each having i) a central planar process fluid layer (30) and ii) two outer planar thermal control fluid layers (40) for containing flowing thermal control fluid and a plurality of illumination modules (50), the illumination modules (50) of said plurality each having a planar form with first and second major surfaces (52, 54) and each comprising at least a first array (60) of semiconductor emitters (70), said emitters (70) positioned to emit from or through the first major surface (52), wherein said first array (60) of semiconductor emitters (70) comprises at least a first emitter (72) and a second emitter (74), the first emitter (72) capable of emitting at a first center wavelength and the second emitter (74) capable of emitting at a second center wavelength, said first and second center wavelengths differing from each other.