The integration of semiconducting materials within thermally drawn multi-material polymer fibers is emerging as a versatile platform for flexible optoelectronics and advanced fabrics. Developing a deeper control over the microstructure of the electrically addressed semiconducting domains has so far been marginally explored. Here we compare a simple annealing treatment of the as-drawn fiber, with a laser-based approach to tailor the microstructure post-drawing. We show that the laser treatment enables better control over the crystallization depth and leads to a microstructure with significantly larger grains. These results are also revealed through optoelectronic characterization, where the better microstructure leads to significantly improved photoresponsivity and photosensitivity, compared to that of regular heat treated fiber, paving the way towards high performance optoelectronic polymer fiber devices.