[EN] The direct integration of crystalline oxide layers into flexible electronic systems requires the development of relatively simple, low-temperature processing routes. Seeding represents a powerful strategy to reach this objective by the generation of preferential sites for the nucleation of crystalline phases with a reduced energy barrier. Here, a novel approach is reported where nanoseeds are generated in-situ from a precursor solution using a solvent-engineering strategy (solvent-antisolvent). The controlled addition of an antisolvent (1,3-propanediol) to a solution of metal salts (Bi/Fe) dissolved in acetic acid results in the formation of nanocrystals (seeds) by supersaturation. The presence of such nanoseeds is also confirmed in the deposited layers, improving significantly the crystallinity of the respective BiFeO3 thin films as complementary deduced by piezoresponse force microscopy. Using this low-temperature strategy, crystalline films are directly grown on flexible polymeric substrates at only 350 ºC showing a remanent polarization of 10.5 μC cm-2 and a clear photovoltaic effect (11.7 μW cm-2) of interest in computer memories and energy harvesters. The flexibility of the BiFeO3 thin films may enlarge the number of applications of this multifunctional, lead-free material in next-generation digital and sustainable electronic devices based on a facile, low-cost fabrication method with a reduced energy consumption., This work is part of the Spanish Projects PID2019-104732RB-I00 and MAT2017-91772-EXP funded by MCIN/AEI/10.13039/501100011033. Grant RYC-2016-20047 funded by MCIN/AEI/10.13039/501100011033. O. B. acknowledges financial support from Spanish "JAE Intro" Programme (JAEINT_19_01923)., Peer reviewed