Controllable Grain Morphology of Perovskite Absorber Film by Molecular Self-Assembly toward Efficient Solar Cell Exceeding 17%

The highly developed crystallization process with respect to perovskite thin films is favorable for efficient solar cells. Here, an innovative intermolecular self-assembly approach was employed to retard the crystallization of PbI₂ in dimethylformamide (DMF) by additional solvent of dimethyl sulfoxide (DMSO), which was proved to be capable of coordinating with PbI₂ by coordinate covalent bond. The obtained PbI₂(DMSO)_<i>x</i> (0 ≤ <i>x</i> ≤ 1.86) complexes tend to be closely packed by means of intermolecular self-assembly. Afterward, an intramolecular exchange of DMSO with CH₃NH₃I (MAI) enabled the complexes to deform their shape and finally to reorganize to be an ultraflat and dense thin film of CH₃NH₃PbI₃. The controllable grain morphology of perovskite thin film allows obtaining a power conversion efficiency (PCE) above 17% and a stabilized power output above 16% within 240 s by controlling DMSO species in the complex–precursor system (CPS). The present study gives a reproductive and facile strategy toward high quality of perovskite thin films and efficient solar cells

Improving the Photovoltage of Blade-Coated MAPbI₃ Perovskite Solar Cells via Surface and Grain Boundary Passivation with π‑Conjugated Phenyl Boronic Acids

High-density electronic defects at the surfaces and grain boundaries (GBs) of perovskite materials are the major contributor to suppressing the power conversion efficiency (PCE) and deteriorating the long-term stability of the solar devices. Hence, the judicious selection of chemicals for the passivation of trap states has been regarded as an effective strategy to enhance and stabilize the photovoltaic performance of solar devices. Here, we systematically investigated the passivation effects of four organic π-conjugated phenylboronic acid molecules: phenylboronic acid, 2-amino phenylboronic acid (2a), 3-amino phenylboronic acid (3a), and 4-amino phenylboronic acid (4a) by adding them into the methylammonium lead iodide (MAPbI3) precursor solution. We found that solar devices with an optimized 5% (mol %) 3a treatment achieve the best passivation effect due to the strong cross-linking ability via hydrogen bonding interactions between the I of the [PbI6]4– octahedral network of perovskite films and the cross-linking terminal groups [−B­(OH)2, (−NH2)] of 3a. Moreover, the lone pair of electrons on the N atom of an amino group of 3a can passivate the uncoordinated Pb2+ defects at the surface/GBs. As a result, the 3a-passivated device shows a high open-circuit voltage of 1.13 V, which is a 14.1% improvement compared to the control device (0.99 V). Moreover, the reduced defect density and improved carrier lifetimes enabled a high PCE of 18.89% in our blade-coated champion inverted structure of MAPbI3 solar cells, with improved long-term stability

High Performance of Perovskite Solar Cells via Catalytic Treatment in Two-Step Process: The Case of Solvent Engineering

Currently, the potential mechanism of the solvent-assisted crystallization for mixed cations perovskite thin film (FA_<i>x</i>MA_1–<i>x</i>PbI₃) prepared via two-step solution-process still remains obscure. Here, we clarified the molecular-competing-reacted process of NH₂CHNH₂I (FAI) and CH₃NH₃I (MAI) with PbI₂(DMSO)_<i>x</i> complex in dimethyl sulfoxide (DMSO) and diethyl ether (DE) catalytic solvent system in the sequential two-step solution-process. The microscopic dynamics was characterized via the characterizations of in situ photoluminescence spectra. In addition, we found that the thermal stability of the perovskite films suffered from the residual solvent with high boiling point, for example, DMSO. The further DE treatment could promote the volatility process of DMSO and accelerate the crystallization process of perovskite films. The highest PCE over 19% with slight hysteresis effect was eventually obtained with a reproducible FA_0.88MA_0.12PbI₃ solar cell, which displayed a constant power output within 100 s upon light soaking and stable PCE output within 30 d in the thermal stability test

Hysteretic Behavior upon Light Soaking in Perovskite Solar Cells Prepared via Modified Vapor-Assisted Solution Process

Recently, the organic–inorganic hybrid perovskite solar cells exhibit rapidly rising efficiencies, while anomalous hysteresis in perovskite solar cells remains unsolvable. Herein, a high-quality perovskite thin film is prepared by a modified vapor-assisted solution process, which is a simple but well-controllable method proven to be capable of producing a thin film with full surface coverage and grain size up to micrometers. The as-fabricated perovskite solar cell has efficiency as high as 10.2%. The hysteresis effects of both planar and mesoscopic TiO₂-based perovskite solar cells have been comprehensively studied upon illumination. The results demonstrate that mesoporous-based perovskite cells combined with remarkable grain size are subject to alleviating the hysteresis effects in comparison to the planar cells. Likewise, mesoscopic TiO₂-based perovskite cells perform independently of illumination and bias conditions prior to the measurements, whereas the planar cells display a reversible behavior of illumination and applied bias-dependent I–V curves. The present study would refer strip road for the stability study of the perovskite solar cells

All-Inorganic CsPbI₂Br Perovskite Solar Cells with High Efficiency Exceeding 13%

All-inorganic perovskite solar cells provide a promising solution to tackle the thermal instability problem of organic–inorganic perovskite solar cells (PSCs). Herein, we designed an all-inorganic perovskite solar cell with novel structure (FTO/NiOx/CsPbI2Br/ZnO@C60/Ag), in which ZnO@C60 bilayer was utilized as the electron-transporting layers that demonstrated high carrier extraction efficiency and low leakage loss. Consequently, the as-fabricated all-inorganic CsPbI2Br perovskite solar cell yielded a power conversion efficiency (PCE) as high as 13.3% with a Voc of 1.14 V, Jsc of 15.2 mA·cm–2, and FF of 0.77. The corresponding stabilized power output (SPO) of the device was demonstrated to be ∼12% and remarkably stable within 1000 s. Importantly, the obtained all-inorganic PSCs without encapsulation exhibited only 20% PCE loss with thermal treatment at 85 °C for 360 h, which largely outperformed the organic-species-containing PSCs. The present study demonstrates potential in overcoming the intractable issue concerning the thermal instability of perovskite solar cells

Underwater Multispectral Computational Imaging Based on a Broadband Water-Resistant Sb₂Se₃ Heterojunction Photodetector

Exploration, utilization, and protection of marine resources are of great significance to the survival and development of mankind. However, currently classical optical cameras suffer information loss, low contrast, and color distortion due to the absorption and scattering nature for the underwater environment. Here, we demonstrate an underwater multispectral computational imaging system combined with single-photodetector imaging algorithm technology and a CdS/Sb2Se3 heterojunction photodetector. The computational imaging technology coupled with an advanced Fourier algorithm can capture a scene by a single photodetector without spatial resolution that avoids the need to rely on high-density detectors array and bulky optical components in traditional imaging systems. This convenient computational imaging method provides more flexible possibilities for underwater imaging and promises to give more imaging capabilities (such as multispectral imaging, antiscattering imaging capability) to meet ever-changing demand of underwater imaging. In addition, the water-resistant CdS/Sb2Se3 heterojunction photodetector fabricated by the close spaced sublimation (Sb2Se3) and chemical bath deposition (CdS) shows excellent self-powered photodetection performance at zero bias with high LDR of 128 dB, broadband response spectrum range of 300–1050 nm, high responsivity up to 0.47 A/W, and high specific detectivity over 5 × 1012 jones. Compared with the traditional optical imaging system, our designed computational imaging system that combines the advanced Fourier algorithm and a high-performance CdS/Sb2Se3 heterojunction photodetector exhibits outstanding antiscattering imaging capability (shielded by frosted glass), weak light imaging capability (∼0.2 μW/cm2, corresponding to moonlight intensity), and multispectral imaging capability. Therefore, we believe that this work will boost the progress of marine science

Nonlinear Optical Response of Organic–Inorganic Halide Perovskites

Metal halide perovskites have exhibited excellent properties as absorbers in solar cells, but this may simply be the first of many applications for this intriguing class of materials. Here, we report the nonlinear optical response of triiodide (CH₃NH₃PbI₃) and mixed halide (CH₃NH₃PbI_3–<i>x</i>Cl_<i>x</i>) perovskite absorbers. The results show that they have large nonlinear refractive index (NRI), 3 orders of magnitude larger than that of silicon. Particularly, the NRI of CH₃NH₃PbI_3–<i>x</i>Cl_<i>x</i> is more than two times larger compared to that of CH₃NH₃PbI₃. Meanwhile, both of them have been proven to possess saturable absorption effects with small nonlinear absorption coefficients which indicate that they can maintain excellent absorption under high-intensity irradiation and are favorable to modulators toward large-energy pulsed laser. Taking into consideration the saturable absorption effect, we demonstrated a pulsed laser with the perovskite as a pulse modulator. These results above indicate the potential for perovskites to be employed in nonlinear optoelectronic devices

Suppressing Nonradiative Losses in Wide-Band-Gap Perovskites Affords Efficient and Printable All-Perovskite Tandem Solar Cells with a Metal-Free Charge Recombination Layer

Although the efficiencies of all-perovskite tandem solar cells have surpassed 26%, further advancement of device performance is constrained by the large photovoltage deficit in wide-band-gap perovskite subcells. Meanwhile, state-of-the-art charge recombination layers incorporate an additional thin metal film (Au or Ag), which not only complexes device fabrication but induces parasitic optical losses. Here, we first fabricate efficient wide-band-gap perovskite solar cells (PSCs) with by suppressing nonradiative losses both in bulk material and at interface. The prepared PSCs with a band gap of 1.71 eV yield an impressive open-circuit voltage (VOC) of 1.27 V, giving a small VOC deficit of 0.44 V and an efficiency of 20.8%. We then fabricate monolithic all-printed perovskite tandem devices by constructing a metal-free recombination layer, which yields an efficiency of 23.65% and a high VOC of 2.05 V. This work offers a simple yet effective charge recombination architecture for advancing the performance of all-perovskite tandem devices