  Silicon photomultipliers (SiPM) are the photon detectors chosen for the
tracking readout in NEXT, a neutrinoless {\beta}{\beta} decay experiment which
uses a high pressure gaseous xenon time projection chamber (TPC). The
reconstruction of event track and topology in this gaseous detector is a key
handle for background rejection. Among the commercially available sensors that
can be used for tracking, SiPMs offer important advantages, mainly high gain,
ruggedness, cost-effectiveness and radio-purity. Their main drawback, however,
is their non sensitivity in the emission spectrum of the xenon scintillation
(peak at 175 nm). This is overcome by coating these sensors with the organic
wavelength shifter tetraphenyl butadienne (TPB). In this paper we describe the
protocol developed for coating the SiPMs with TPB and the measurements
performed for characterizing the coatings as well as the performance of the
coated sensors in the UV-VUV range.
