Integration of Sustainable Carbon Nanoparticles Into Inverted Hybrid Perovskite Solar Cells to Enhance Optoelectronic Performance

Hybrid Perovskite Solar Cells (HPSCs) using lead halide perovskites offer high performance and low-cost fabrication via solution processes. However, their environmental and thermal instability, along with poor polycrystalline quality-such as trap states and grain boundaries-limit device efficiency. In this study, we propose four novel compositions of carbon nanoparticles (CNPs) as additives for methylammonium PbI₃ (MAPI)-based HPSCs to enhance the optoelectronic performance. The CNPs are synthesized through a green, cost-effective method using citric acid and L-tryptophan for nitrogen doping. Their optical, structural, and morphological properties are thoroughly characterized prior to integration. To assess the impact of CNPs on perovskite crystallization and facet orientation, synchrotron-based 2D Grazing-Incidence Wide-Angle X-ray Scattering (GIWAXS) is employed. Devices are fabricated using an inverted architecture, suitable for flexible substrates and energy-efficient processing. Electrical and electrochemical impedance spectroscopy analyses reveal improved fill factors across all CNP compositions. The optimized system achieves a power conversion efficiency (PCE) of 10%, compared to 8.2% for the reference device without CNPs, confirming the potential of green CNPs to enhance HPSC performance without compromising structural integrity.