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Despite the ongoing breakthroughs in power conversion efficiency (PCE) of perovskite solar cells (PSCs), the presence of inherent defects in perovskite films remains the predominant hurdle impeding the further progress of this promising photovoltaic technology. Herein, we propose a straightforward yet highly effective additive strategy to passivate the bulk defects of perovskite films. Specifically, based on the two-step deposition method, a functional polymer poly(2-ethyl-2-oxazoline) (PEOXA) was introduced into the PbI2 precursor solution, facilitating the formation of the PbI2-dimethyl sulfoxide phase. This solvate facilitates subsequent intercalation reactions with organic cations, resulting in the formation of high-quality perovskite films. Additionally, due to its abundant active sites and larger molecular size, PEOXA forms a three-dimensional network structure at the perovskite grain boundaries, effectively connecting the grains and suppressing ion migration. The C = O groups in PEOXA passivate the uncoordinated Pb2+ defects at the grain boundaries, inhibiting non-radiative charge recombination in the bulk. As a result, the device PCE increased from 22.02% to 24.27%. Furthermore, the PEOXA-based PSCs exhibited excellent operational stability, retaining 86% of the initial efficiency after continuous operation for 1500 h. [ABSTRACT FROM AUTHOR]

Enhancing crystallinity, passivating the grain boundary and interfacial defects have been validated to be critical for improving the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). Herein, a synergetic co‐modulation and co‐passivation strategy is proposed to simultaneously enhance crystallinity and passivate the grain boundary and surface defects of FAPbI3 based PSCs. The 4‐fluoro‐phenethylammonium iodide (4‐F‐PEAI) added in precursor solution and poly (9‐vinylcarbazole) (PVK) added in antisolvent can jointly modulate the crystallization of FAPbI3 films. The 4‐F‐PEAI‐derived 2D perovskite, which is spontaneously formed at the grain boundaries of FAPbI3, can passivate the defects effectively. In the meantime, PVK left on top of a FAPbI3 layer can passivate the surface defects and meanwhile function as an interfacial barrier layer between FAPbI3 and hole transport layer (HTL) to mitigate the detrimental interfacial charge recombination. With the holistic benefit of the enhanced crystallinity, reduced defects and trap sites, and mitigated non‐radiative recombination and suppressed ion migration, the encouraging PCEs up to 21.6% is achieved for the resulting modified PSCs. Additionally, this strategy endows the device with notably enhanced operational stability under continuous exposure to illumination, with more than 84% of the initial PCE being maintained after continuous illumination for 800 h. [ABSTRACT FROM AUTHOR]

TiO2 as an efficient electron transfer material has been widely utilized in dye-sensitized solar cells (DSSCs), and the morphology of TiO2 plays a decisive role in the performance of DSSCs. However, one-dimensional TiO2 nanowires, which are generally used as the efficient electron transport layers, have small specific surface area and low dye loading. Here, we introduce an effective and reproducible one-step hydrothermal method to prepare TiO2 nanowire with nanoscale whiskers. The synthetic sample was characterized by the field emission scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction. TiO2 nanowire with nanoscale whiskers has a high light scattering performance and high dye loading capacity. This novel TiO2 nanowire show a power conversion efficiency (PCE) of 4.12%, which is close to the benchmark of P25 nanoparticle usually used in DSSC fabrication. The PCE of DSSC-3 using TiO2 nanowire with nanoscale whiskers and commercial P25 double-layer photoanode has a PCE of 5.98%, showing an increase of 11.98% when compared with DSSC-2 based on pure P25 photoanode. [ABSTRACT FROM AUTHOR]