A method of forming a three-dimensional object can be carried out by: (a) providing a carrier and an optically transparent member having a build surface, the carrier and the build surface defining a build region therebetween; (b) filling the build region with a polymerizable liquid, the polymerizable liquid comprising: (i) a polymerizable component; (ii) upconverting particles that are excited by light at a first wavelength and upon excitation emit light at a second wavelength that is shorter than the first wavelength; and (iii) a photoiniator that catalyzes polymerization of the polymerizable component upon excitation by light at the second wavelength; (c) irradiating the build region through the optically transparent member with an excitation light at the first wavelength, and optionally but in some embodiments preferably also advancing the carrier away from the build surface, wherein the excitation light is temporally and/or spatially modulated, to thereby form the three-dimensional object from the polymerizable liquid.