Effect of Photocrosslinking of D-A Thiophene Copolymers on the Performance of Single-Material Solar Cells

Side-chain C60-fullerene functionalized alkylthiophene copolymers with different regioregularity and fullerene content are successfully synthesized using a simple and straightforward post-polymerization functionalization procedure based on a Grignard coupling reaction. The products are employed as single materials in photoactive layers of organic photovoltaic solar cells. The use of double-cable polymers allows an enhanced control on the nanomorphology of the active blend, reducing the phase-segregation phenomena as well as the macroscale separation between the electron acceptor and donor components. With the insertion of a thin layer of gold nanoparticles between buffer and active layer of the cells, a conversion efficiency of 5.68% is obtained. Moreover, an increased stability over time is achieved when the copolymers are photocrosslinked immediately after the annealing procedure, leading to acceptable efficiencies even after 80 h of accelerated ageing, a key feature for widespread applicability of the prepared devices.