N -(2-aminoethyl) Acetamide Additive Enables Phase-Pure and Stable α-FAPbI3 for Efficient Self-Powered Photodetectors

Controlling Interfacial Amidation Reaction Rate to Regulate Crystal Growth toward High-Performance FAPbBr3-Based Inverted Light-Emitting Diodes

Controlling interfacial reactions is critical for zinc oxide (ZnO)-based inverted perovskite light-emitting diodes (PeLEDs), boosting the external quantum efficiency (EQE) of the near-infrared device to above 20%. However, violent interfacial reactions between the bromine-based perovskites and ZnO-based films severely limit the performance of inverted green PeLEDs, whose efficiency and stability lag far behind those of their near-infrared counterparts. Here, a controllable interfacial amidation between the bromine-based perovskites and magnesium-doped ZnO (ZnMgO) film utilizing caprylyl sulfobetaine (SFB) is realized. The SFB molecules strongly interact with formamidinium bromide, decelerating the amidation reaction between formamidinium and carboxylate groups on the ZnMgO film, thus regulating the crystallization of FAPbBr3. Combined with the passivation of benzylamine, a FAPbBr3 bulk film directly deposited on a ZnMgO substrate with single-crystal characteristics is obtained, exhibiting a high photoluminescence quantum yield of above 80%. The resultant PeLEDs demonstrate a peak EQE of exceeding 20% at a high luminance of 120,000 cd m-2 and a half lifetime of 26 min at 11,000 cd m-2, representing the state-of-the-art inverted green electroluminescence. This work resolves the crucial issues of violent interfacial reactions and provides a strategy toward inverted green PeLEDs with outstanding performance.

Surface Passivation to Enhance the Interfacial Pyro-Phototronic Effect for Self-Powered Photodetection Based on Perovskite Single Crystals

The interfacial pyro-phototronic effect (IPPE) presents a novel approach for improving the performance of self-powered photodetectors (PDs) based on metal halide perovskites (MHPs). The interfacial contact conditions within the Schottky junctions are crucial in facilitating the IPPE phenomenon. However, the fabrication of an ideal Schottky junction utilizing MHPs is a challenging endeavor. In this study, we present a surface passivation method aimed at enhancing the performance of self-powered photodetectors based on inverted planar perovskite structures in micro- and nanoscale metal-halide perovskite SCs. Our findings demonstrate that the incorporation of a lead halide salt with a benzene ring moiety for surface passivation leads to a substantial improvement in photoresponses by means of the IPPE. Conversely, the inclusion of an alkane chain in the salt impedes the IPPE. The underlying mechanism can be elucidated through an examination of the band structure, particularly the work function (WF) modulated by surface passivation. Consequently, this alteration affects the band bending and the built-in field (VBi) at the interface. This strategy presents a feasible and effective method for producing interfacial pyroelectricity in MHPs, thus facilitating its potential application in practical contexts such as energy conversion and infrared sensors.

Strain Regulation and Defect Passivation of FA-Based Perovskite Materials for Highly Efficient Solar Cells

Formamidine lead triiodide (FAPbI3 ) perovskites have attracted increasing interest for photovoltaics attributed to the optimal bandgap, high thermal stability, and the record power conversion efficiency (PCE). However, the materials still face several key challenges, such as phase transition, lattice defects, and ion migration. Therefore, external ions (e.g., cesium ions (Cs+ )) are usually introduced to promote the crystallization and enhance the phase stability. Nevertheless, the doping of Cs+ into the A-site easily leads to lattice compressive strain and the formation of pinholes. Herein, trioctylphosphine oxide (TOPO) is introduced into the precursor to provide tensile strain outside the perovskite lattice through intermolecular forces. The special strain compensation strategy further improves the crystallization of perovskite and inhibits the ion migration. Moreover, the TOPO molecule significantly passivates grain boundaries and undercoordinated Pb2+ defects via the forming of P═O─Pb bond. As a result, the target solar cell devices with the synergistic effect of Cs+ and TOPO additives have achieved a significantly improved PCE of 22.71% and a high open-circuit voltage of 1.16 V (voltage deficit of 0.36 V), with superior stability under light exposure, heat, or humidity conditions.

Cesium Cyclopropane Acid-Aided Crystal Growth Enables Efficient Inorganic Perovskite Solar Cells with a High Moisture Tolerance

While all-inorganic halide perovskites (iHPs) are promising photovoltaic materials, the associated water sensitivity of iHPs calls for stringent humidity control to reach satisfactory photovoltaic efficiencies. Herein, we report a moisture-insensitive perovskite formation route under ambient air for CsPbI2 Br-based iHPs via cesium cyclopropane acids (C3 ) as a compound introducer. With this approach, appreciably enhanced crystallization quality and moisture tolerance of CsPbI2 Br are attained. The improvements are attributed to the modified evaporation enthalpy of the volatile side product of DMA-acid initiated by Cs-acids. As such, the water-involving reaction is directed toward the DMA-acids, leaving the target CsPbI2 Br perovskites insensitive to ambient humidity. We highlight that by controlling the C3 concentration, the dependence of power conversion efficiency (PCE) in CsPbI2 Br devices on the humidity level during perovskite film formation becomes favorably weakened, with the PCEs remaining relatively high (>15 %) associated with improved device stability for RH levels changed from 25 % to 65 %. The champion solar cells yield an impressive PCE exceeding 17 %, showing small degradations (<10 %) for 2000 hours of shell storage and 300 hours of 85/85 (temperature/humidity) tests. The demonstrated C3 -based strategy provides an enabler for improving the long-sought moisture-stability of iHPs toward high photovoltaic device performance.

Mixed-Cation Halide Perovskite Doped with Rb+ for Highly Efficient Photodetector

Photodetectors are widely employed as fundamental devices in optical communication, automatic control, image sensors, night vision, missile guidance, and many other industrial or military fields. Mixed-cation perovskites have emerged as promising optoelectronic materials for application in photodetectors due to their superior compositional flexibility and photovoltaic performance. However, their application involves obstacles such as phase segregation and poor-quality crystallization, which introduce defects in perovskite films and adversely affect devices' optoelectronic performance. The application prospects of mixed-cation perovskite technology are significantly constrained by these challenges. Therefore, it is necessary to investigate strategies that combine crystallinity control and defect passivation to obtain high-quality thin films. In this study, we incorporated different Rb⁺ ratios in triple-cation (CsMAFA) perovskite precursor solutions and studied their effects on crystal growth. Our results show that a small amount of Rb⁺ was enough to induce the crystallization of the α-FAPbI₃ phase and suppress the formation of the yellow non-photoactive phase; the grain size increased, and the product of the carrier mobility and the lifetime (μτ) improved. As a result, the fabricated photodetector exhibited a broad photo-response region, from ultraviolet to near-infrared, with maximum responsivity (R) up to 11.8 mA W^-1 and excellent detectivity (D*) values up to 5.33 × 10¹¹ Jones. This work provides a feasible strategy to improve photodetectors' performance via additive engineering.