Optoelectronic and Morphological Surface Resistance Evaluation of Laser-Induced Graphene Counter Electrodes for Potential Applications in Cesium Lead Halide Perovskite Solar Cells

This study investigates the physicochemical, optical, and electrical characterization of laser-induced graphene (LIG) samples for integration as counter electrodes in cesium lead halide perovskite solar cells. The impact of laser processing parameters on electrode performance is explored, including laser power, laser speed, and beam defocus. Density functional theory (DFT) computational modeling is employed for atomistic investigation and work function estimation, demonstrating the density of states (DOS), quantum capacitance of the graphene sheets, and energy work function. NiO is utilized as a hole transport layer, and the energy work function of LIG is tuned accordingly. SEM measurements estimate thin film porosity, and optical testing assesses back reflection capabilities in terms of backward scattering. The surface resistance of various samples is tested using a scanning four-probe station concerning FTO-coated glass. A figure of merit is introduced to evaluate the backward scattering due to the porous medium. The macroscopic trade-off between the counter electrode’s role as a back reflector and the losses due to surface resistance is addressed. Ultimately, a full perovskite solar cell was constructed, incorporating LIG as a counter electrode, achieving an overall efficiency of 12.52%.