The DUNE experiment, currently under construction in the US, has a broad physics program that
spans from oscillation physics at the GeV scale to the observation of solar neutrinos in few-MeV
events. This program leverages the unprecedented resolution and imaging capability of the liquid
argon TPC. LArTPCs are dense, fully-active detectors, that allow for a 3D real-time reconstruction
of the events, achieved by means of the collection of drifted electrons from ionization. In addition
to electrons, LArTPCs produce large quantities of VUV photons, which will be fully exploited
in DUNE thanks to its Photon Detection System (PDS). The light collected by the PDS will
be of paramount importance to measure the event timing and the vertical trajectory of charged
particles for non-beam events, and will improve significantly the overall energy resolution of
DUNE, especially at low energies, allowing to unlock its full scientific potential. The last few
years marked important steps in the development of the PDS. Thanks to an intense R&D effort
conducted at the two ProtoDUNE detectors at CERN, the PDS technology for DUNE has been
optimized and validated for the DUNE physics. This article illustrates the concept of the DUNE
PDS, its development and use in ProtoDUNE, as well as its role in achieving the physics goals of
DUNE.