Series Resistance Modulation for Large‐Area Fully Printable Mesoscopic Perovskite Solar Cells

Perovskite solar cells (PSCs) have achieved a certified power conversion efficiency (PCE) of 25.5% and show potential for low‐cost photovoltaic applications. One key of pushing PSCs into industrialization is enlarging their areas. However, the PCE of larger‐area PSCs is dramatically limited by the undesired increase in series resistance (R_S), which leads to obvious loss of fill factor (FF). Herein, R_S in fully printable mesoscopic PSCs is modulated with a carbon electrode by optimizing the device geometry, preparing busbars to collect currents from electrodes and improving the conductivity of the back electrode. A rectangular device shape and tin busbars on conductive substrate effectively reduce the R_S. Meanwhile, an additional hot‐pressed highly conductive low‐temperature carbon layer on the back carbon electrode also reduces the R_S. An enhanced PCE of 13.99% for 1 cm² PSCs by R_S modulation is obtained, whereas the control device exhibits a PCE of 7.74%. The PCE increase is due to the improvement of FF from 0.372 to 0.638 with reduced R_S from 27.13 to 9.66 Ω cm².