No abstract

Organic halide salt passivation is considered to be an essential strategy to reduce defects in state-of-the-art perovskite solar cells (PSCs). This strategy, however, suffers from the inevitable formation of in-plane favored two-dimensional (2D) perovskite layers with impaired charge transport, especially under thermal conditions, impeding photovoltaic performance and device scale-up. To overcome this limitation, we studied the energy barrier of 2D perovskite formation from ortho-, meta- and para-isomers of (phenylene)di(ethylammonium) iodide (PDEAI2) that were designed for tailored defect passivation. Treatment with the most sterically hindered ortho-isomer not only prevents the formation of surficial 2D perovskite film, even at elevated temperatures, but also maximizes the passivation effect on both shallow- and deep-level defects. The ensuing PSCs achieve an efficiency of 23.9% with long-term operational stability (over 1000 h). Importantly, a record efficiency of 21.4% for the perovskite module with an active area of 26 cm2 was achieved.

Incorporation of alkali metals such as Cs + , Rb + , and K + into hybrid organic−inorganic halide lead perovskites (HOIPs) generally improves the optoelectronic properties of HOIPs. However, it is still uncertain how alkali metals interact and distribute within the HOIPs. There is also a struggle in finding a technique for nanometer-scale structural and chemical characterization without laborious sample preparation or risking severe beam damage of the material during characterization. Here, we have investigated the nanometer-scale distribution of alkali pairs (K−Cs, Rb−Cs, and K−Rb) incorporated into a HOIP using helium-ion microscopy coupled with secondary-ion mass spectrometry (HIM−SIMS) that allows for nanometer-scale elemental and morphological imaging at an unprecedented spatial resolution. HIM−SIMS analysis reveals that Rb segregates at perovskite grain boundaries irrespective of whether it is paired with Cs or K.

Remarkable progress in power conversion efficiency of perovskite solar cells (PSCs) has been achieved over the last decade, reaching 25.5%. However, transferring these accomplishments from individual small-size devices into large-area modules while preserving their commercial competitiveness compared to other thin-film solar cells remains a challenge. A major obstacle is to reduce the resistive losses and the number of intrinsic defects of electron transport layers (mesoporous TiO2, ETL) and to fabricate high-quality large-area perovskite films. Here, we report a facile solvothermal method to synthesize single-crystalline TiO2 rhombus-like nanoparticles with exposed {001} facets. Owing to their low lattice mismatch with the perovskite absorber, high electron mobility and lower density of defects, single-crystalline TiO2 nanoparticle-based small-size devices (0.09 cm2) achieve an efficiency of 24.05% and a fill factor of 84.7%. Importantly, these devices maintain about 90% of their initial performance after continuous operation for 1400 h. Combined with vacuum quenching-assisted techniques, we have fabricated large-area modules and obtained a certified efficiency of 22.72% with an active area of nearly 24 cm2. This represents the highest efficiency modules with the lowest efficiency loss between small-size devices and modules, enabling to reproducibly fabricate stable and efficient PSC modules.

Strontium titanate (STO) is a well-known oxide used in a wide variety of applications due to its excellent stability and optoelectronic properties. However, its integration in photoelectrocatalytic devices is limited by the lack of fast and scalable methods to produce robust films at a low temperature and atmospheric pressure. Herein, we report an atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD) approach for the synthesis of STO crystalline films and their applications for photoelectrochemical solar energy conversion. The film crystallinity, which plays a determinant role in the photoelectrochemical performance, was linked to the selected strontium precursor and injection method. Through thermal stability studies of the precursors [Sr(dpm), Sr(ipo), Sr(acac), and Ti(ipo)] and analysis of the solution droplet size, it was demonstrated that the closer thermal decomposition behavior and superior miscibility of the Sr(dpm) and Ti(ipo) precursors led to more homogeneous and crystalline films with the highest photoelectrochemical performance (16.5 μA cm −2 at 1.23 V vs RHE under 100 mW cm −2 ), which can be further improved by a factor of 3.4 using thermal annealing at 500 °C. Evidence of the impact of a strontium precursor on the properties of STO films is provided through thermogravimetric analysis, X-ray diffraction, energy-dispersive system, UV−vis, X-ray photoelectron spectroscopy, HIM-SIMS, and photoelectrochemical analysis.