A watch incorporating an assembly (70) including a light sensor (72), including a photovoltaic cell, a negative electrode (78) and a positive electrode (79). The assembly has a first portion (52A), in which the electrodes are arranged, and a second portion (54A) which is not included in the first portion and which comprises or covers an antenna (80). The semiconductor material wafer extends into the first and second portions, and all the electrodes are arranged below the semiconductor material wafer. Preferably, this semiconductor material wafer or layer has no conductive doping in the second portion. The wafer, or layer, determines, together with additional layers provided thereon, the homogeneous colour and uniform appearance of the assembly from the side of its upper surface. Also, a dial formed by such an assembly.