A regulation strategy of self-assembly molecules for achieving efficient inverted perovskite solar cells.

Self-assembled monolayers (SAMs) have been successfully employed to enhance the efficiency of inverted perovskite solar cells (PSCs) and perovskite/silicon tandem solar cells due to their facile low-temperature processing and superior device performance. Nevertheless, depositing uniform and dense SAMs with high surface coverage on metal oxide substrates remains a critical challenge. In this work, we propose a holistic strategy to construct composite hole transport layers (HTLs) by co-adsorbing mixed SAMs (MeO-2PACz and 2PACz) onto the surface of the H2O2-modified NiOx layer. The results demonstrate that the conductivity of the NiOx bulk phase is enhanced due to the H2O2 modification, thereby facilitating carrier transport. Furthermore, the hydroxyl-rich NiOx surface promotes uniform and dense adsorption of mixed SAM molecules while enhancing their anchoring stability. In addition, the energy level alignment at the interface is improved due to the utilization of mixed SAMs in an optimized ratio. Furthermore, the perovskite film crystal growth is facilitated by the uniform and dense composite HTLs. As a result, the power conversion efficiency of PSCs based on composite HTLs is boosted from 22.26% to 23.16%, along with enhanced operational stability. This work highlights the importance of designing and constructing NiOx/SAM composite HTLs as an effective strategy for enhancing both the performance and stability of inverted PSCs.

High-Performance Flat-Panel Perovskite X-ray Detectors Enabled by Defect Passivation in Ruddlesden-Popper Perovskites.

Halide perovskites have emerged as promising candidates in X-ray detection due to their strong X-ray absorption and excellent optoelectronic properties. The development of sensitive and stable flat-panel X-ray detectors with high resolution is crucial for practical applications. In this paper, we introduce a novel flat-panel X-ray detector that integrates quasi-two-dimensional (2D) Ruddlesden-Popper (RP) perovskite with a pixeled thin film transistor (TFT) backplane. We incorporate 2,5-dibromopyrimidine (DBPM) as an additive to passivate the Lewis acid defects in the quasi-2D RP perovskite. This modification results in suppressed ion migration, improved optoelectronic performance, and enhanced operational stability of the device. Impressively, the activation energy of the RP perovskite increases from 0.96 to 1.35 eV with the DBPM additive. As a result, X-ray detectors exhibit a high sensitivity of ∼13,600 µC Gyair-1 cm-2, a low detection limit of 6.56 nGyair s-1, and excellent operational stability. Moreover, the flat-panel detectors demonstrate a high spatial resolution of 3.7 line pairs per millimeter and excellent X-ray imaging properties under a remarkably low X-ray dose of ∼50 µGyair, which is just half of the X-ray dose typically used in commercial equipment. This study opens new avenues for the development of flat-panel perovskite X-ray detectors with significant potential for various applications.

A-Site Cation Engineering of Ruddlesden-Popper Perovskites for Stable, Sensitive, and Portable Direct Conversion X-ray Imaging Detectors.

Perovskite flat-panel X-ray detectors are promising products for realizing low-dose medical imaging, a nondestructive test, and security inspection. However, the perovskite X-ray imager still faces intractable problems such as severe baseline drift, a low signal-to-noise ratio, and rapid performance degradation, which were involved by the notorious intrinsic ion migration of the perovskite functional layer. In this work, sensitive, stable, and portable pixel quasi-two-dimensional (2D) Ruddlesden-Popper (RP) perovskite X-ray imagers were obtained by an advanced solvent-free laminated fabrication approach. A-Site cation engineering of RP perovskites provides a hint for solving the trade-off between stability and detection performance, resulting in a stable pixel X-ray imager that shows a sensitivity of ∼7000 µC Gyair-1 cm-2, a detection limit of 7.8 nGyair s-1, and good 2D multipixel X-ray imaging. This work demonstrates both a high-performance, stable X-ray imager and its robust fabrication, paving the way for adopting a RP perovskite imager as novel flat-panel X-ray detectors.

Simultaneous achievement of defect passivation and carrier transport promotion by using emerald salt for methylammonium-free perovskite solar cells.

Defect passivation along with promoted charge transport is potentially an effective but seldom exploited strategy for high-performance perovskite solar cells (PSCs). Herein, the in situ defect passivation and carrier transport improvement are simultaneously realized by introducing a conductive polymer (i.e., emerald salt, ES) into the precursor solution of methylammonium (MA)-free perovskites. The interaction between ES and uncoordinated Pb2+ reduces defect density to suppress the non-radiative recombination. Moreover, ES can act as a "carrier driver" to promote the carrier transport due to its conductive feature, resulting in efficient PSC devices with a decent power conversion efficiency (PCE) of 23.0%, which is among the most efficient MA-free PSCs. The ES-based unencapsulated devices show superior stability, retaining 89.1% and 83.8% of their initial PCEs when subjected to 35 ± 5% relative humidity (RH) storage and 85 °C thermal aging for 1000 h, respectively. To further assess the large-area compatibility of our strategy, 5 × 5 cm2 mini modules were also fabricated, delivering an impressive efficiency of 19.3%. This work sheds light on the importance of conductive additives in boosting cell performance by playing multiple roles in passivating defects, retarding the moisture invasion, and enhancing and balancing charge transport.