Liquid-phase epitaxial (LPE) growth of low-bandgap III-V antimonides is developed for thermophotovoltaic and other optoelectronic device applications. Epitaxial layers of AlGaAsSb, InGaAsSb, and InAsSbP, with thicknesses up to 200 mu m, can be grown in a single LPE step. TPV devices based on InAsSbP extend the spectral response to a wavelength of 3500 nm. These single-epilayer structures are compatible with post-growth zinc diffusion processes that produce high-performance TPV devices. Thick epitaxial layers are also conducive for epilayer film transfer to surrogate substrates and subsequent removal of the GaSb and InAs seeding substrate. An insulating surrogate substrate facilitates isolation schemes for monolithic series-interconnected TPV arrays, and a reflective substrate acting as a backside mirror is used to effect photon recycling.