Perovskite solar cells (PSCs) have attracted great research interest in the scientific community due to their extraordinary optoelectronic properties and the fact that their power conversion efficiency (PCE) has increased rapidly in recent years, surpassing other 3rd generation photovoltaic (PV) technologies. Graphitic carbon nitride (g-C₃N₄) presents exceptional optical and electronic properties and its use was recently expanded in the field of PSCs. The addition of g-C₃N₄ in the perovskite absorber and/or the electron transport layer (ETL) resulted in PCEs exceeding 22%, mainly due to defects passivation, improved conductivity and crystallinity as well as low charge carriers’ recombination rate within the device. Significant performance increase, including stability enhancement, was also achieved when g-C₃N₄ was applied at the PSC interfaces and the observed improvement was attributed to its wetting (hydrophobic/hydrophilic) nature and the fine tuning of the corresponding interface energetics. The current review summarizes the main innovations for the incorporation of graphitic carbon nitride in PSCs and highlights the significance and perspectives of the g-C₃N₄ approach for emerging highly efficient and robust PV devices.

Recently, perovskite solar cells (PSCs) have been widely investigated as an efficient alternative for silicon solar cells. In this work, a proposed modified triple-diode model (MTDM) for PSCs modeling and simulation was used. The Bald Eagle Search (BES) algorithm, which is a novel nature-inspired search optimizer, was suggested for solving the model and estimating the PSCs device parameters because of the complex nature of determining the model parameters. Two PSC architectures, namely control and modified devices, were experimentally fabricated, characterized and tested in the lab. The I–V datasets of the fabricated devices were recorded at standard conditions. The decision variables in the proposed optimization process are the nine and ten unknown parameters of triple-diode model (TDM) and MTDM, respectively. The direct comparison with a number of modern optimization techniques including grey wolf (GWO), particle swarm (PSO) and moth flame (MFO) optimizers, as well as sine cosine (SCA) and slap swarm (SSA) algorithms, confirmed the superiority of the proposed BES approach, where the Root Mean Square Error (RMSE) objective function between the experimental data and estimated characteristics achieves the least value.

One of the key strategies for record photovoltaic efficiencies in metal halide perovskite solar cells is the addition of PbI2 excess in a stoichiometric perovskite solution which controls crystallization, passivates defects and induces a preferred orientation in the perovskite layer. However, residual PbI2, typically found in the perovskite layer after crystallization, generates non-radiative recombination centres and promotes ion migration under light and heating stress, thus accelerating performance loss. To mitigate the above issues, a common strategy is the post-deposition of organic ammonium salts which interact in situ with residual PbI2. Here, we adopt a multifunctional alkylammonium salt, 2-diethylaminoethanethiol hydrochloride (DEAET), in which both the thiol (–SH) and protonated tertiary amine groups can strongly bind to PbI₂. Upon deposition of DEAET on top of FAPbI3 film, we show that DEAT decreases the percentage of residual PbI2 by 40% and totally eliminates Pb0. These two effects lead to enhanced radiative recombination, proving a net passivation effect, while chemical analysis (FTIR and liquid-state NMR) explains that this is due to strong interactions between tertiary protonated ammonium (-NH+) and thiol (-SH) groups of DEAT with under-coordinated Pb2+. The stabilization of FAPbI3 black phase along with the establishment of a solid barrier to impede the infiltration of moisture into the perovskite layer over time lead to enhanced operational stability for the as-fabricated solar cells. The encouraging findings of this study lay the foundation for the utilization of tertiary ammonium thiol-based salts as efficient agents for interface engineering in perovskite solar cells.