Fibers of the biopolymer poly(lactic acid) (PLA) and the p-type semiconducting polymer poly(3-hexylthiophene) (P3HT) were fabricated using the electrospinning technique at low PLA concentration (5 wt%) in CHCl3. The fibers were several millimeters long and had diameters in the range 100 nm-4 mu m. Nanofibers containing 63%/37% of PLA/P3HT were electroactive, and therefore were used to construct p-n diodes whose ideality parameter was 2.4 and rectification (on/off) ratio was 400 at +/- 1 V. These diodes were also able to sense UV radiation and remain operable with an increase in the on/off ratio and a lowering of the turn-on voltage. By fabricating reusable and low-cost multifunctional diodes from PLA/P3HT, the applications of PLA as a biocompatible and biodegradable polyester are expanded to include electronic device fabrication with low environmental impact. (c) 2016 Society of Chemical Industry