Effective Carbon Composite Electrode for Low‐Cost Perovskite Solar Cell with Inorganic CuIn0.75Ga0.25S2 Hole Transport Material

Perovskite solar cells are well known for being low cost, solution‐based, and efficient solar cells; however, the high price of the conventional hole‐collector electrode (Spiro‐OMeTAD/Gold) and the high price and complexity of depositing gold on large scales are major barriers against commercializing them. Herein, an effective carbon composite electrode is introduced for a low‐cost perovskite solar cell with CuIn 0.75 Ga 0.25 S 2 hole transport material to solve this problem. The carbon electrode is deposited by the doctor blade method using a paste composed of flakes of graphite, carbon black, and a kind of hydrophobic polymer (polystyrene or poly‐methyl methacrylate). It is investigated how the weight ratio of carbon black to graphite and type of binder affect sheet resistance and resistivity of carbon composite layer. The effects of carbon electrode composition on the charge transport resistance at the CuIn 0.75 Ga 0.25 S 2 /perovskite interface are investigated using impedance spectroscopy in different light intensities of white light and light with different wavelengths of 530, 660, and 740 nm. The best efficiency of 15.9% is obtained for the champion cell (fabricated outside the glovebox), which is close to the best efficiency of the reference cell with conventional Spiro‐OMeTAD/Gold hole‐collector that is 16.3%.