A photovoltaic device (1;1';1") comprising: • a solar cell unit including: - a working electrode comprising a porous light-absorbing layer arranged at a top side of the solar cell unit, - a first conducting layer for extracting photo-generated electrons from the light-absorbing layer, wherein the light-absorbing layer is arranged on top of the first conducting layer, - a porous substrate made of an insulating material, wherein the first conducting layer is formed on one side of the porous substrate, - a counter electrode including a second conducting layer arranged at a bottom side of the solar cell unit, wherein the second conducting layer is formed on an opposite side of the porous substrate, and - a conducting medium for transferring charges between the second conducting layer and the light-absorbing layer, • a first conductor (7; 7b) in electrical contact with the first conducting layer, • a second conductor (8; 8a, 8b; 8c) in electrical contact with the second conducting layer, and an encapsulation encapsulating the solar cell unit and comprising an at least partly transparent top sheet covering the top side of the solar cell unit and a bottom sheet covering the bottom side of the solar cell unit, wherein the second conductor (8; 8a, 8b; 8c) is arranged between the second conducting layer and the bottom sheet of the encapsulation at the bottom side of the solar cell unit, characterised in that the first conductor (7, 7b) is arranged between the porous substrate and the bottom sheet at the bottom side of the solar cell unit, the first conductor is electrically insulated from the second conducting layer, and a part of the porous substrate comprises conducting material disposed between the first conductor (7;7b and the first conducting layer to provide electrical contact between the first conductor and the first conducting layer. • a solar cell unit including: - a working electrode comprising a porous light-absorbing layer arranged at a top side of the solar cell unit, - a first conducting layer for extracting photo-generated electrons from the light-absorbing layer, wherein the light-absorbing layer is arranged on top of the first conducting layer, - a porous substrate made of an insulating material, wherein the first conducting layer is formed on one side of the porous substrate, - a counter electrode including a second conducting layer arranged at a bottom side of the solar cell unit, wherein the second conducting layer is formed on an opposite side of the porous substrate, and - a conducting medium for transferring charges between the second conducting layer and the light-absorbing layer, - a working electrode comprising a porous light-absorbing layer arranged at a top side of the solar cell unit, - a first conducting layer for extracting photo-generated electrons from the light-absorbing layer, wherein the light-absorbing layer is arranged on top of the first conducting layer, - a porous substrate made of an insulating material, wherein the first conducting layer is formed on one side of the porous substrate, - a counter electrode including a second conducting layer arranged at a bottom side of the solar cell unit, wherein the second conducting layer is formed on an opposite side of the porous substrate, and - a conducting medium for transferring charges between the second conducting layer and the light-absorbing layer, • a first conductor (7; 7b) in electrical contact with the first conducting layer, • a second conductor (8; 8a, 8b; 8c) in electrical contact with the second conducting layer, and