The effect of carbon counter electrodes on fully printable mesoscopic perovskite solar cells

Mesoporous graphite/carbon black counter electrodes (CEs) using flaky graphite with different sizes were applied in hole-conductor-free mesoscopic perovskite solar cells by a screen-printing technique. Conductivity measurements, current-voltage characteristics, and impedance spectroscopy measurements were carried out to study the influence of CEs on the photovoltaic performance of devices. The results indicated that graphite, which acted as the conductor in carbon counter electrodes (CCEs), could significantly affect the square resistance of CCEs, thus resulting in differences in fill factor and power conversion efficiency (PCE) of the devices. Based on the optimized CCEs with a thickness of 9 mm, PCEs exceeding 11% could be achieved for the fully printable hole-conductor-free mesoscopic perovskite solar cells due to the low square resistance and large pore size of graphite based CCEs. The abundant availability, low cost and excellent properties of such carbon material based CEs offer a wide prospect for their further applications in perovskite solar cells.