Improved Photo(electro)chemical Response and Solar Cell Performance of (ThEA)₂PbI₄-Based Layered Perovskites by Reduced Graphene Oxide (rGO)

Three-dimensional (3D) lead halide perovskites have evolved as a champion light-harvesting material in the race of third-generation solar cells within a decade due to their excellent optoelectronic properties. Instability due to moisture is one of the daunting issues, creating challenges toward the commercialization of 3D perovskite solar cells. On the other hand, pure two-dimensional (2D) layered perovskites show significant potential for photovoltaic applications, exhibiting moisture resistance properties, compared to 3D perovskites. However, these pure 2D layered perovskites exhibit poor device performance due to the long nonconductive carbon chain present inherently in the structure of light-absorbing perovskites. Reduced graphene oxide (rGO) has attracted attention due to its high electrical conductivity in addition to its inexpensive synthesis methods. In this study, we have examined the effect of rGO as an “interlayer” in R 2 PbI 4 (where R = thiophene ethylamine)-based 2D layered perovskite solar cells (conventional n–i–p configuration) and during photo(electro)chemical analysis of R 2 PbI 4 (coated over compact TiO 2 - and mesoporous TiO 2 -coated fluorine-doped tin oxide (FTO) photoanodes). The perovskite layer was fabricated by a one-step spin coating method and characterized using X-ray diffraction (XRD), UV–visible, scanning electron microscopy (SEM), and atomic force microscopy (AFM) instruments. The role of rGO as an interlayer was observed in (i) decreasing the charge transfer resistance, (ii) decreasing the photoluminescence (PL) intensity, (iii) enhancing the photocurrent density during photo(electro)chemical analysis, and (iv) improving the efficiencies of solar cells of 2D layered perovskites.