Universal Strategy for Improving Perovskite Photodiode Performance: Interfacial Built-In Electric Field Manipulated by Unintentional Doping

Buried Grating Enables Fast Response Self-Powered Polarization-Sensitive Perovskite Photodetectors for High-Speed Optical Communication and Polarization Imaging

Polarization-sensitive perovskite photodetectors (PSPPDs) have demonstrated great potential for acquiring multidimensional data in remote sensing, security, and optical communication fields. However, requirements of external power supplies and polarization systems, slow response, and poor long-term stability restrict PSPPDs' further development. Herein, a self-powered PSPPD with buried grating structures induced by ultrafast laser direct writing is designed. Remarkably, polarization detection can be achieved without the assistance of conventional optical and mechanical structures. The buried grating structure can reduce light reflection through grating diffraction, facilitating light convergence and enhancing light trapping within the active layer of the PSPPD. As expected, the PSPPD exhibits excellent external quantum efficiency (532 nm, 0 V bias), responsivity (532 nm, 0 V bias), and dark current values of 93.93%, 403 mA W-1, and 5.95 × 10-10 A, respectively. Notably, the raising/falling time is less than 2 µs, which is one of the shortest response times among PSPPDs with grating structures to the best of this knowledge. Moreover, after 120 days of air exposure, the manufactured PSPPDs remain highly effective in fast optical communications, manifesting their exciting potential to produce reliable, high-performance devices economically and efficiently for future applications.

All-Inorganic Perovskite Solar Cells: Defect Regulation and Emerging Applications in Extreme Environments

All-inorganic perovskite solar cells (PSCs), such as CsPbX3, have garnered considerable attention recently, as they exhibit superior thermodynamic and optoelectronic stabilities compared to the organic-inorganic hybrid PSCs. However, the power conversion efficiency (PCE) of CsPbX3 PSCs is generally lower than that of organic-inorganic hybrid PSCs, as they contain higher defect densities at the interface and within the perovskite light-absorbing layers, resulting in higher non-radiative recombination and voltage loss. Consequently, defect regulation has been adopted as an important strategy to improve device performance and stability. This review aims to comprehensively summarize recent progresses on the defect regulation in CsPbX3 PSCs, as well as their cutting-edge applications in extreme scenarios. The underlying fundamental mechanisms leading to the defect formation in the crystal structure of CsPbX3 PSCs are firstly discussed, and an overview of literature-adopted defect regulation strategies in the context of interface, internal, and surface engineering is provided. Cutting-edge applications of CsPbX3 PSCs in extreme environments such as outer space and underwater situations are highlighted. Finally, a summary and outlook are presented on future directions for achieving higher efficiencies and superior stability in CsPbX3 PSCs.

A Catalyst-Like System Enables Efficient Perovskite Solar Cells

High-quality perovskite films are essential for achieving high performance of optoelectronic devices; However, solution-processed perovskite films are known to suffer from compositional and structural inhomogeneity due to lack of systematic control over the kinetics during the formation. Here, the microscopic homogeneity of perovskite films is successfully enhanced by modulating the conversion reaction kinetics using a catalyst-like system generated by a foaming agent. The chemical and structural evolution during this catalytic conversion is revealed by a multimodal synchrotron toolkit with spatial resolutions spanning many length scales. Combining these insights with computational investigations, a cyclic conversion pathway model is developed that yields exceptional perovskite homogeneity due to enhanced conversion, having a power conversion efficiency of 24.51% for photovoltaic devices. This work establishes a systematic link between processing of precursor and homogeneity of the perovskite films.

Improving the performance of perovskite solar cells using a dual-hole transport layer

The energy loss (Eloss) caused by inefficient charge transfer and large energy level offset at the buried interface can easily restrict the performance of p-i-n perovskite solar cells (PVSCs). In this study, the utilization of poly-TPD and P3CT-N as a dual-hole transporting layer (HTLs) was implemented in a sequential manner. This approach aimed to improve the charge transfer efficiency of the HTL and mitigate charge recombination at the interface between the HTL and PVK. The results showed that this strategy also could achieve more suitable energy levels, improve the quality of the perovskite film layer, and ultimately enhance the device's stability. IPVSCs employing the dual-HTLs approach exhibited the highest power conversion efficiency of 19.85%, and the open-circuit voltage increased to 1.09 V from 1.00 V. This study offers a straightforward and efficient approach to boost the device performance by minimizing Eloss and reducing the buried interfacial defects. The findings underscore the potential of employing a dual-HTL strategy as a promising pathway for further advancements in PVSCs.

Molecular Synergistic Passivation for Efficient Perovskite Solar Cells and Self-Powered Photodetectors

The interface between the perovskite and electron-transporting material is often treated for defect passivation to improve the photovoltaic performance of devices. A facile 4-Acetamidobenzoic acid (containing an acetamido, a carboxyl, and a benzene ring)-based molecular synergistic passivation (MSP) strategy is developed here to engineer the SnOx /perovskite interface, in which dense SnOx are prepared using an E-beam evaporation technology while the perovskite is deposited with vacuum flash evaporation deposition method. MSP engineering can synergistically passivate defects at the SnOx /perovskite interface by coordinating with Sn4+ and Pb2+ with functional group CO in the acetamido and carboxyl. The optimized solar cell devices can achieve the highest efficiency of 22.51% based on E-Beam deposited SnOx and 23.29% based on solution-processed SnO2 , respectively, accompanied by excellent stability exceeding 3000 h. Further, the self-powered photodetectors exhibit a remarkably low dark current of 5.22 × 10-9  A cm-2 , a response of 0.53 A W-1 at zero bias, a detection limit of 1.3 × 1013  Jones, and a linear dynamic range up to 80.4 dB. This work proposes a molecular synergistic passivation strategy to enhance the efficiency and responsivity of solar cells and self-powered photodetectors.

Insight into efficient photoluminescence regulation mechanism by lattice distortion and Mn2+ doping in organic-inorganic hybrid perovskites

The space configurations of organic ammonium cations play a vital role in indirectly revealing the relationship between the structures and photoluminescence properties. Structural transformation induced tunability of the photophysical properties has rarely been reported. In this work, two organic-inorganic halide perovskites with different octahedral distortions were synthesized to explore the relationships between "steric effect" of organic cations and photoluminescence properties. The broadband emission of (DETA)PbBr₅·H₂O with high octahedral distortion is attributed to self-trapped excitons and trap states, whereas smaller steric hindrance ammonium cation 1,4-butanediamine form a 2D layered perovskite with narrowband emission due to free excitons. More importantly, the photoactive metal ions Mn²⁺ doping strategy gives rise to tunable broadband light emission from weak to strong orange emission with higher PLQY up to 20.96 % and 12.90% in 0D (DETA)Pb_0.2Mn_0.8Br₅·H₂O and 2D (BDA)Pb_0.8Mn_0.2Br₄ respectively. Combined with time-correlated single photon counting and photoluminescence spectra, Mn-doped perovskites reveal energy transfer from host to Mn²⁺ characteristic energy level (⁴T₁-⁶A₁). Importantly, defect states are reduced by doping manganese ions in (DETA)PbBr₅·H₂O to enhance photoluminescence intensity. This work sheds light on the mechanism of defect-related emission and provides a successful strategy for designing novel and adjustable materials.

A Perovskite Photodetector Crossbar Array by Vapor Deposition for Dynamic Imaging

With the development of perovskite photodetectors, integrating photodetectors into array image sensors is the next target to pursue. The major obstacle to integrating perovskite photodiodes for dynamic imaging is the optoelectrical crosstalk among the pixels. Herein, a perovskite photodiode-blocking diode (PIN-BD) crossbar array with pixel-wise rectifying property by the vapor deposition method is presented. The PIN-BD shows a large rectification ratio of 3.3 × 10² under illumination, suppressing electrical crosstalk to as small as 8.0% in the imaging array. The fast response time of 72.8 ns allows real-time image acquisition by over 25 frames per second. The imaging sensor exhibits excellent imaging capability with a large linear dynamic range of 112 dB with 4096 gray levels and weak light sensitivity under 1.2 lux.

Impact of Cesium Concentration on Optoelectronic Properties of Metal Halide Perovskites

Performance of a perovskite solar cell is largely influenced by the optoelectronic properties of metal halide perovskite films. Here we study the influence of cesium concentration on morphology, crystal structure, photoluminescence and optical properties of the triple cation perovskite film. Incorporation of small amount (x = 0.1) of cesium cations into Csx(MA0.17FA0.83)1−x Pb(I0.83Br0.17)3 leads to enhanced power conversion efficiency (PCE) of the solar cell resulting mainly from significant rise of the short-current density and the fill factor value. Further increase of Cs concentration (x > 0.1) decreases the film’s phase purity, carrier lifetime and correspondingly reduces PCE of the solar cell. Higher concentration of Cs (x ≥ 0.2) causes phase segregation of the perovskite alongside with formation of Cs-rich regions impeding light absorption.