Nanoscale interfacial engineering of 1D g-C₃ N₄ enables effective and thermally stable HTL-free carbon-based perovskite solar cells with aging for 100 hours

Carbon-based perovskite solar cells (PSCs) have exhibited unprecedented progress in the past decades, however, the deficit of open-circuit voltage and non-radiative recombination losses are the dominating limiting factors in scaling up the devices in view of commercialization. The researchers and scientists recognize the dominating factors and propose different themes to overcome the limiting factors. Among the different solutions, interfacial engineering of PSCs between the interfaces of transporting layer (electron or hole) and perovskite influences the reduction of non-radiative recombination losses with improvement in device efficiency. In this work, one-dimensional (1D) graphitic carbon nitride (g-C₃N₄) is synthesized through simple pyrolysis using two different mediums (ethanol and ethylene glycol). 1D g-C₃N₄ is interfaced between electron transport layer and perovskite absorber influences effectively in fine-tuning the work function by aligning the energy level of the fabricated mixed halide PSCs. Nanoscale engineered 1D g-C₃N₄ interfacial layer supports boosting the power conversion efficiency of the PSCs to 5.20% and 7.14% for tube and layered tube structures at ambient conditions. Further, the interfacial layer aids in improving thermal (tube: ~59.80%; layered tube: ~74.50%) and photostability (tube: ~78.65%; layered tube: ~87.25%) characteristics of the fabricated devices for 100 h duration at ambient conditions. Highlights: One-dimensional tubular and layered nanotubes shaped graphitic carbon nitride (1D g-C₃N₄) were successfully synthesized. The synthesized 1D g-C₃N₄ has been efficiently used as an interfacial layer for the first time. The 1D growth of the tube and layer nanostructured interface modified PSC devices were found to be of excellent charge transfer and charge injection at the (c-TiO₂/perovskite) interface. A maximum PCE of ~7.14% (V_OC = 0.532 V, J_sc = 18.23 mA/cm², and FF = 0.736) was achieved by the introduced 1D g-C₃N₄ interlayer resulting in the reduced surface traps on the perovskite layer. A drop in the PCE of just ~20% decrease in its initial PCE value when measured after the period of 100 hours evidencing the thermal stability of the interface modified PSC device compared to that of the bare device.