Photomultiplier-tubes work on the principle of the photoelectric effect and they can detect Cherenkov light.  However, PMT also produce background signals due to internal effects, called dark noise. Dark noise dominates the signal in any given PMT by several orders of magnitude, negatively affecting the ability of an array of photo-sensors to detect neutrinos. The dark noise rate is strongly dependent on the PMT's ambient temperature. A potential solution to this is thermoelectric coolers.