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A research hotspot for the last decade, organometal‐halide perovskites are now showing their promise in numerous optoelectronic devices. With power conversion efficiency (PCE) greater than 25%, perovskite solar cells (PSCs) are approaching the status of popular monocrystalline silicon–based solar cells (SCs). However, the presence of a bioaccumulative lead (Pb) in these perovskite compounds hinders their scalability and commercialization. The endeavor on nontoxic alternatives has triggered a new field of perovskites where Pb has been successfully eliminated. Preliminary studies of photovoltaic (PV) devices based on Pb‐free perovskites have shown some promise; however, they failed to exhibit comparable performance and compositional stability. Therefore, to exploit together the advantages of high efficiency and lesser toxicity, combinations of Pb alternatives with each other as well as with conventional Pb are required in the perovskite framework to fabricate hybrid perovskites (HPVKs). The first part of this Review briefly discusses all possible Pb substitutes and their limitations in PV devices. Based on the Pb contents, the second part elaborates on the two different types of HPVKs (i.e., nontoxic and less toxic) and their progress in photovoltaics. The Review concludes with an outlook discussing current challenges in the way of HPVKs and prospective opportunities to assess their future progress. [ABSTRACT FROM AUTHOR]

Organometal halide perovskites (OMHPs) have shown promising applications in solar cells, light-emitting diodes, and photodetectors. However, besides the toxic lead, the intensive usage of organic solvents during their fabrication could induce severe environmental pollution. Therefore, green-solvent fabrication of OMHPs is highly desirable but extremely challenging. Herein, we report aqueous phase fabrication and conversion of laurionite-type Pb(OH)Br into CH3NH3PbBr3. The prepared CH3NH3PbBr3 crystals show prominently enhanced environmental and thermal stability compared to those prepared in organic phases. To demonstrate the application of the prepared CH3NH3PbBr3, a resistive switching memory device (ReRAM) is fabricated. The ReRAM devices exhibit good bipolar non-volatile characteristics that can remain unchanged for more than 30 days under ambient conditions. We believe that the aqueous phase-based green fabrication process of OMHPs will not only greatly alleviate the environmental pollution during or after their commercialization process, but will also provide a new concept in stabilizing and improving the performance of OMHP-based devices. [ABSTRACT FROM AUTHOR]

Organometal halide perovskites (PVKs) have demonstrated their potential in photovoltaics in terms of higher photovoltaic efficiency, aiming to achieve the Shockly-Quieser limit of a single-junction solar cell. Understanding the photo-optical and structural properties of PVKs is crucial to further improving their photovoltaic efficiency. Defects-free PVKs with a suitable energy bandgap (E BG ∼ 1.34 eV) are desirable to capture most of the solar radiations; however, the E BG of the state-of-the-art PVKs is not the ideal one. Compositional engineering offers E BG tunability but decreases carrier lifetime and increases material instability. The application of hydrostatic pressure is a green route, which initiates structural changes in the PVKs and tunes their E BG , leading to the emergence of interesting material properties, including piezochromism, metallization, photoresponsivity, and structural stability. Therefore, understanding the interplay between pressure-induced electronic and structural changes is crucial. Herein, the pressure-induced modifications in structural and optoelectronic properties are elaborated. Particularly, pressure-induced properties in single crystals, lower-dimensional PVKs, and all-inorganic PVKs are comprehended. Moreover, PVK amorphization and strain-induced properties of various PVK materials are also summarized. The review is concluded with an outlook discussing the challenges associated with the pressure induction on PVK material and our perspective to resolve these issues and future work. [ABSTRACT FROM AUTHOR]

• Dodecylammonium chloride assisted the formation of compact lead-free perovskites films. • The crystallinity and stoichiometric defects of the films are significantly improved. • Enhanced optical absorption, photoluminescence, and extended carrier lifetime is achieved. • Solar cell device exhibited a highest PCE for the solution-processed Cs 3 Bi 2 I 9 -based devices. • Photovoltaic device demonstrated an enhanced environmental stability in the ambient air. Bismuth is considered as one of the most promising candidates to replace Pb in the organo-lead halide perovskite, a classical material for various optoelectronic applications. When utilized in a photovoltaic cell, the performance of the cell drops due to deterioration in the absorber film and the changes in its crystal structures. In this work, a small amount of dodecylammonium chloride, C 12 H 25 NH 3 Cl (DCl) is added into Cs 3 Bi 2 I 9 (CBI), resulting in a pinhole-free high-quality perovskite (PVK) film via a single-step solution processability, also confirmed by FTIR and XPS analyses. Structural, optical, and microscopic analyses showed that the quality, surface features, and crystallinity of the CBI films are significantly improved by adding DCl. The prepared films are successfully demonstrated in a solar cell and exhibited considerably improved photovoltaic (PV) characteristics (V OC by ~47%, J SC by ~33%, FF by 13%, and PCE by 115%) over pure CBI-based devices. Moreover, the PV device retained more than 95% of its initial PCE in the ambient laboratory environment (relative humidity 55±5%). To the best of our knowledge, this is the highest PCE along with extended environmental stability reported for solution processed CBI-based perovskite solar cells. [ABSTRACT FROM AUTHOR]

• Ambient environment synthesis of the hybrid perovskites films and solar cells. • Addition of Dodecylammonium for the 1st time into the triple cation perovskites. • HPVKs thin films showed stablility for 50 days in relative humidity well above 50%. • HPVKs thin films showed stablility to high thermal stress of 85 ℃ for 24 h. • Solar-cell made of HPVKs yielded a PCE of 5%. • PCE of the solar cell retained up to 64% for 9 days in RH > 50% and 85 ℃. Owing to their high efficiency and extended environmental stability, hybrid 2D/3D-perovskites (HPVKs) are gaining an increasing interest in the field of organometal halide perovskite solar cells (PSCs). In HPVKs, the 3D component acts as an active material, where its 2D-counterpart provides protection against environmental factors. Here in, we add dodecylammonium-chloride (DACl) into the precursor solution of 3D-perovskites (FAMAPbI 3) to achieve HPVKs. The formation of HPVK is confirmed by XRD, optical absorption, and Fourier-transform infrared (FTIR) spectroscopies. The structural and optical analysis affirmed that in the case of HPVKs, not only the crystallinity of perovskites is improved significantly but also a variation in its structural properties and optical bandgap have occurred. It is also observed that the surface morphologies of HPVK films are considerably improved with the incorporation of DACl. A minute amount of CsI is also added into the precursor solution of HPVKs, which further assist the formation of HPVKs and consequently causes a significant increase in the carrier lifetime. Finally, a solar cell made of HPVKs shows an improved PCE than pure 3D-perovskites. All HPVKs films and solar-cells are prepared in the ambient humidity and found to be more hydrophobic and stable, not only under relative humidity >50% but also under high thermal stress of 85 ℃. [ABSTRACT FROM AUTHOR]

In recent years CdTe thin film solar cells (SCs) have demonstrated promising market application foreground. However, a relatively large gap between the achieved SCs efficiencies and the theoretically predicted maximum efficiency still exists. In particular, the open circuit voltage (V oc ) of the CdTe thin film SCs could be further increased, which is limited by high-work-function of CdTe. In this work, p-type narrow-gap SnTe thin films are proposed as a buffer layer in the back contact of CdTe SCs. The band alignment at SnTe/CdTe interface renders a small valance band offset, which expedites hole transport from the CdTe absorber to the hole electrode and improves the Ohmic contact for CdTe. With the insertion of a SnTe single buffer layer at the back contact, a Cu-free CdTe SC has been developed, which displays the same cell efficiency as the traditional cells using Cu x Te as the back contact. The V oc of cells with ZnTe: Cu/SnTe double-layer at back contact is notably higher than the CdTe SCs fabricated with Cu x Te or ZnTe: Cu single-layer at the back contact. Furthermore, accretion of hole concentration is also demonstrated by the diffusion of Sn in the CdTe absorber layer. This work shows the potential to improve CdTe SCs by using a narrow-gap IV-VI compound semiconductor. [ABSTRACT FROM AUTHOR]