Provided are conformable light delivery devices for increasing light penetration depth and related methods. The device comprises a tissue penetrating member having a distal end and a proximal end, the tissue penetrating member configured to penetrate the tissue of the patient to be inserted into the tissue, wherein the tissue penetrating member is at least partially optically transparent along a surface of the tissue penetrating member positioned between the distal end of the tissue penetrating member and the proximal end of the tissue penetrating member to provide optical transmission of at least a portion of the light through the surface of the tissue penetrating member, thereby allowing at least the portion of the light to be delivered into the tissue of the patient when the tissue penetrating member is inserted into the tissue; and a substrate that supports the tissue penetrating member.