We present results from deep Spitzer/Infrared Array Camera (IRAC) observations of 28 metal-poor, strongly star-forming galaxies selected from the DEEP2 Galaxy Survey. By modelling infrared and optical photometry, we derive stellar masses and other stellar properties. We determine that these metal-poor galaxies have low stellar masses, $M_{star}$ $approx10^{8.1}$-$10^{9.5}$ $M_{odot}$. Combined with the Balmer-derived star formation rates (SFRs), these galaxies have average inverse SFR/$M_{star}$ of $approx$100 Myr. The evolution of stellar mass-gas metallicity relation to $zapprox0.8$ is measured by combining the modelled masses with previously obtained spectroscopic measurements of metallicity from [O III] $lambda$4363 detections. Here, we include measurements for 79 galaxies from the Metal Abundances across Cosmic Time Survey. Our mass-metallicity relation is lower at a given stellar mass than at $z=0.1$ by 0.27 dex. This demonstrates a strong evolution in the mass-metallicity relation, $(1+z)^{-1.45^{+0.61}_{-0.76}}$. We find that the shape of the $zapprox0.8$ mass-metallicity relation, a steep rise in metallicity at low stellar masses, transitioning to a plateau at higher masses, is consistent with $zsim0.1$ studies. We also compare the evolution in metallicity between $zapprox0.8$ and $zsim0.1$ against recent strong-line diagnostic studies at intermediate redshifts and find good agreement. Specifically, we find that lower mass galaxies ($4times10^8$ $M_{odot}$) built up their metal content 1.6 times more rapidly than higher mass galaxies ($10^{10}$ $M_{odot}$). Finally, we examine whether the mass-metallicity relation has a secondary dependence on SFR, and statistically concluded that there is no strong secondary dependence for $zapprox0.8$ low-mass galaxies.
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