The influence of composition and carbon types on the electrical conductivity of carbon-based conductive pastes for deposition as back-electrode in perovskite solar cells

• Activated carbon (AC) was synthesized from sugarcane leave biomass by chemical activation and pyrolysis. • The AC is a mixture of amorphous and graphitic phases with some surface oxygen groups, showing particles with large surface area and mixed micropores and mesopores. • Carbon compositions including activated carbon (AC), Vulcan carbon black (VCB) and graphite (G) as well as total carbon content in fabricated carbon pastes influenced the electrical conductivity of the carbon electrode formed. • Carbon pastes effectively deposited as electrode in planar hole-transport-layer-free perovskite solar cells with structure Glass/FTO/c-TiO 2 /mp-TiO 2 /CH 3 NH 3 PbI 3 /C exhibited an open circuit voltage of 0.9 V under simulated illumination of AM 1.5 G, 100 mW/cm 2 . Carbon-based electrodes are promising replacements of expensive, vacuum deposited noble metals in perovskite solar cells (PSCs) because of their low cost, chemical inertness and durability. This study is aimed at determining the influence of carbon composition on the electrical conductivity of carbon electrode and application in carbon-based C-PSC. Activated carbon (AC) was synthesized from sugarcane leaves and used to prepare different carbon pastes compositions. The AC was characterized by x-ray diffraction, microstructural and elemental analyses, Fourier Transform Infrared and Raman spectroscopies, and nitrogen sorption isotherms to assess surface area and micropore volumes. Results show that the AC is mostly amorphous with small graphitic component, having oxygen surface groups and extended surface area with micropores. AC was found to serve as linking layers in AC/graphite (G) carbon pastes, giving a maximum electrical conductivity of 36.9 Ω -1 cm -1 for a 27 % AC in AC/G mixture. The use of different carbon materials G, AC, CB (carbon black) and also a higher total carbon amount showed augmented conductivity of 47.7 Ω -1 cm -1 for an AC:CB:G weight ratio of 0.5:0.5:3. The carbon pastes were effectively deposited as counter electrode in planar hole-transport-layer-free PSC with structure Glass/FTO/c-TiO 2 /mp-TiO 2 /CH 3 NH 3 PbI 3 /C. The C-PSC exhibited an open circuit voltage of 0.9 V under simulated illumination of AM 1.5 G, 100 mW/cm 2 similar to reference devices using mesoporous TiO 2 as electron-transport-material. The results show that AC obtained from biomass can be utilized to prepare low cost and solvent friendly carbon pastes which can be effectively deposited as electrode in devices such as PSC. Activated carbon (AC) synthesized from biomass and was mixed with graphite (G) and carbon black (CB) in different weight ratios to prepare carbon pastes, CP. The CP with ratio of 0.5:0.5:3 of AC:CB:G respectively was deposited as electrode on glass substrate and showed electrical conductivity of 47.7 Ω -1 cm -1 while when deposited as counter electrode in planar perovskite solar cell device with structure Glass/FTO/c-TiO 2 /mp-TiO 2 /CH 3 NH 3 PbI 3 /C exhibited an open circuit voltage of 0.9 V.