We propose and demonstrate the first large-area tandem semi-transparent photosensitive nanocrystal skins (PNSs) on flexible substrate operates on the principle of photogenerated potential buildup without applying any external bias, consequently there is no current-matching limitation between the junctions. We fabricated the tandem PNS composed of only one monolayer of colloidal water soluble CdTe and that of CdHgTe nanocrystals in adjacent junctions on top of a Kapton polymer tape. Owing to the usage of a single NC layer in each junction, noise generation is significantly reduced while keeping the film considerably transparent. The top semi-transparent electrodes on each junction accumulate the photogenerated holes while the photogenerated electrons are trapped inside the nanocrystals. The resulting tandem PNS has an open-circuit photovoltage buildup equal to the sum of the two single-junctions demonstrating a photovoltage buildup of 128.4 mV for an excitation intensity of 75.8 μW/cm2 at 350 nm. The flexible PNS can be bent to a 3.5 mm radius of curvature and cut in arbitrary shapes without damaging the operation of the cut parts and without introducing any significant loss in the total sensitivity. These skins are expected to be used as building blocks to construct low-cost, flexible, large-area UV/visible/NIR sensing devices with highly efficient full-spectrum conversion.