Toward pursuing high‐performance photodetectors based on 2D transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2), it is desirable to reduce the high dark current and sluggish response time. Here, in multilayer MoS2‐based photodetectors, a 2D halide perovskite, (C6H5C2H4NH3)2PbI4 ((PEA)2PbI4), is introduced as a bifunctional material: both as electron reservoir to reduce free carriers and passivation agent to passivate defects. Surprisingly, dark current is suppressed by six orders of magnitude after coating a (PEA)2PbI4 thin layer onto pristine MoS2 photodetector, with the dark current decreased to 10−11 A. This huge reduction of dark current suggests an efficient interlayer charge transfer from MoS2 to (PEA)2PbI4, which is further verified by photoluminescence quenching phenomenon. It indicates that (PEA)2PbI4 serves as electron reservoir to reduce carrier density of MoS2, resulting in ultrahigh detectivity (1.06 × 1013 Jones). Moreover, the response speed is also accelerated by more than 100‐fold due to passivation by 2D perovskite. In addition, it is found that this type of photodetectors can further work at self‐power mode (with the bias of 0 V). Therefore, the strategy of applying 2D perovskite on the surface of TMDs provides a novel way to fabricate high‐performance photodetectors.

With the capability to manipulate the built‐in field in solar cells, ferroelectricity is found to be a promising attribute for harvesting solar energy in solar cell devices by influencing associated device parameters. Researchers have devoted themselves to the exploration of ferroelectric materials that simultaneously possess strong light absorption and good electric transport properties for a long time. Here, it is presented a novel and facile approach of combining state‐of‐art light absorption and electric transport properties with ferroelectricity by the incorporation of room temperature 1D ferroelectric perovskite with 3D organic–inorganic hybrid perovskite (OIHP). The 1D/3D mixed OIHP films are found to exhibit evident ferroelectric properties. It is notable that the poling of the 1D/3D mixed ferroelectric OIHP solar cell can increase the average Voc can be increased from 1.13 to 1.16 V, the average PCE from 20.7% to 21.5%. A maximum power conversion efficiency of 22.7%, along with an enhanced fill factor of over 80% and open‐circuit voltage of 1.19 V, can be achieved in the champion device. The enhancement is by virtue of reduced surface recombination by ferroelectricity‐induced modification of the built‐in field. The maximum power point tracking measurement substantiates the retention of ferroelectric‐polarization during the continued operation.

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Realization of remote wearable health monitoring (RWHM) technology for the flexible photodiodes is highly desirable in remote-sensing healthcare systems used in space stations, oceans, and forecasting warning, which demands high external quantum efficiency (EQE) and detectivity in NIR region. Traditional inorganic photodetectors (PDs) are mechanically rigid and expensive while the widely reported solution-processed mixed tin-lead (MSP) perovskite photodetectors (PPDs) exhibit a trade-off between EQE and detectivity in the NIR region. Herein, a novel functional passivating antioxidant (FPA) strategy has been introduced for the first time to simultaneously improve crystallization, restrain Sn 2+ oxidization, and reduce defects in MSP perovskite films by multiple interactions between thiophene-2-carbohydrazide (TAH) molecules and cations/anions in MSP perovskite. The resultant solution-processed rigid mixed Sn-Pb PPD simultaneously achieves high EQE (75.4% at 840 nm), detectivity (1.8 × 10 12 Jones at 840 nm), ultrafast response time (t rise /t fall = 94 ns/97 ns), and improved stability. This work also highlights the demonstration of the first flexible photodiode using MSP perovskite and FPA strategy with remarkably high EQE (75% at 840 nm), and operational stability. Most importantly, the RWHM is implemented for the first time in the PIN MSP perovskite photodiodes to remotely monitor the heart rate of humans at rest and after-run conditions.

A facile acetic acid modification is introduced to passivate the defects at the SnO2/perovskite interface, thus improving the device performance.

Quasi-2D perovskites have attracted extensive attention due to their extraordinary stability compared to their 3D counterparts. Presently, the bottleneck in quasi-2D perovskite solar cells is their relatively low efficiency. The intrinsic interior carrier transport in the perovskite layer consisting of disorderly oriented phases and inadequate optimization of interfacial carrier transfer have greatly limited the overall device performance. A comprehensive study on effective phase manipulation in the BA2MA4Pb5I16 (n = 5) quasi-2D perovskites is presented to pursue optimal efficiency. With the assistance of the solvent DMSO in a constant thermal-annealing spin-coating (CTAS) process, the crystalline growth process in the quasi-2D perovskite film is effectively manipulated and delicate energy band alignment by eliminating the n ≤ 2 phases at the bottom surface has been successfully achieved. Consequently, a significant improvement of carrier transport in the perovskite layer and photogenerated hole extraction at the interface has been accomplished. The champion device exhibited a boosted PCE of 17.66%.

The photovoltaic performance of perovskite solar cell is determined by multiple interrelated factors, such as perovskite compositions, electronic properties of each transport layer and fabrication parameters, which makes it rather challenging for optimization of device performances and discovery of underlying mechanisms. Here, we propose and realize a novel machine learning approach based on forward-reverse framework to establish the relationship between key parameters and photovoltaic performance in high-profile MASnxPb1-xI3 perovskite materials. The proposed method establishes the asymmetrically bowing relationship between band gap and Sn composition, which is precisely verified by our experiments. Based on the analysis of structural evolution and SHAP library, the rapid-change region and low-bandgap plateau region for small and large Sn composition are explained, respectively. By establishing the models for photovoltaic parameters of working photovoltaic devices, the deviation of short-circuit current and open-circuit voltage with band gap in defective-zone and low-bandgap-plateau regions from Shockley-Queisser theory is captured by our models, and the former is due to the deep-level traps formed by crystallographic distortion and the latter is due to the enhanced susceptibility by increased Sn4+ content. The more difficulty for hole extraction than electron is also concluded in the models and the prediction curve of power conversion efficiency is in a good agreement with Shockley-Queisser limit. With the help of search and optimization algorithms, an optimized Sn:Pb composition ratio near 0.6 is finally obtained for high-performance perovskite solar cells, then verified by our experiments. Our constructive method could also be applicable to other material optimization and efficient device development.

Two-dimensional (2D) perovskite materials are a promising platform to construct high performance photodetectors due to their novel structure, high stability, resistance to ion migration and decent light harvesting ability.