Surface modification of organic-inorganic halide perovskite thin films represents a promising approach to enhance the efficiency and stability of perovskite solar cells. Here, we synthesized ...N-methyl-1,3-propane diammonium diiodide (Me-PDAI2) and found that Me-PDA2+ can template a three-dimensional “perovskitoid” structure (Me-PDA)Pb2I6. Simple surface treatment with Me-PDAI2 on top of a standard (FAPbI3)0.85(MAPbI2Br)0.10(CsPbI3)0.05 perovskite induces the formation of a thin (Me-PDA)Pb2I6 perovskitoid surface layer, leading to smoother surface texture, longer charge-carrier lifetime, higher charge-carrier mobility, and a reduced surface-defect density. With the perovskitoid surface modification, the device efficiency is significantly improved from 20.3% to 22.0% along with enhanced stability in both shelf life (ISOS-D-1 stability) and operation (ISOS-L-1 stability). We further demonstrated that the perovskitoid surface engineering approach is applicable to various perovskite compositions, including CsFAMA-, FAMA-, and MA-based lead halide perovskites, making perovskitoid an important design motif for perovskite surface engineering for enhanced device performance and stability.
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•A 3D “perovskitoid” structure (Me-PDA)Pb2I6 is reported•Simple surface treatment with Me-PDAI2 on 3D perovskite leads to better properties•Device efficiency is improved from 20.3% to 22.0% along with enhanced stability•Perovskitoid surface treatment can be applied to various perovskite compositions
The post-treatment by bulky alkyl-ammonium halides forming a Low-D capping layer on the 3D perovskite is promising to improve the performance of perovskite solar cells (PSCs). However, the energy offset and the insulating nature associated with such surface treatments can hinder charge transfer across the LD/3D heterojunction. Thus, it is critical to have new designs of surface engineering approaches with enhanced out-of-plane charge transport to further advancing the efficiency and stability of PSCs. In this work, we reported, for the first time, the 3D perovskitoid (Me-PDA)Pb2I6 surface layer modification by a simple surface treatment with Me-PDAI2 on top of a 3D perovskite thin film, leading to smoother surface texture, longer charge-carrier lifetime, higher charge-carrier mobility, and reduced surface-defect density. With the perovskitoid surface modification, the device efficiency is improved from 20.3% to 22.0% along with enhanced stability.
A simple surface treatment with N-methyl-1,3-propane diammonium diiodide (Me-PDAI2) on top of 3D perovskite inducing the formation of a thin 3D (Me-PDA)Pb2I6 perovskitoid layer is reported, leading to smoother surface texture, longer charge-carrier lifetime, higher charge-carrier mobility, and reduced surface-defect density. With the perovskitoid surface modification, the device efficiency is improved from 20.3% to 22.0% along with enhanced stability. In addition, the perovskitoid surface engineering approach is applicable to different perovskite compositions.
Organic–inorganic (O–I) heterostructures, consisting of atomically thin inorganic semiconductors and organic molecules, present synergistic and enhanced optoelectronic properties with a high ...tunability. Here, we develop a class of air-stable vertical O–I heterostructures comprising a monolayer of transition-metal dichalcogenides (TMDs), including WS2, WSe2, and MoSe2, on top of tetraphenylethylene (TPE) core-based aggregation-induced emission (AIE) molecular rotors. The created O–I heterostructures yields a photoluminescence (PL) enhancement of up to ∼950%, ∼500%, and ∼330% in the top monolayer WS2, MoSe2, and WSe2 as compared to PL in their pristine monolayers, respectively. The strong PL enhancement is mainly attributed to the efficient photogenerated carrier process in the AIE luminogens (courtesy of their restricted intermolecular motions in the solid state) and the charge-transfer process in the created type I O–I heterostructures. Moreover, we observe an improvement in photovoltaic properties of the TMDs in the heterostructures including the quasi-Fermi level splitting, minority carrier lifetime, and light absorption. This work presents an inspiring example of combining stable, highly luminescent AIE-based molecules, with rich photochemistry and versatile applications, with atomically thin inorganic semiconductors for multifunctional and efficient optoelectronic devices.
In article number 2001136, Michael V. Mirkin, Nathan R. Neale, and co‐workers modulate hydrogen evolution reaction (HER) activity by adding transition metal ions M to a titanium nitride MXene to ...yield M‐Ti4N3Tx (M = V, Cr, Mo, or Mn). The M‐Ti4N3Tx MXenes exhibit highly tunable metal‐dependent HER activity from the basal planes as well as semiconducting behavior measured using scanning electrochemical microscopy and electrochemical techniques. Artwork credit: Al Hicks (NREL).
We report on the synthesis and characterization of CdS window layers grown by close-space sublimation (CSS) method for CdS/CdTe thin-film solar cells. Comparing with CdS window layers grown by other ...methods such as sputtering and chemical bath deposition, CSS-grown CdS layers can facilitate the consumption of CdS layers and suppress the diffusion of Te into CdS window layers. CSS-grown CdS layers exhibit much larger grains with faceted morphology. Due to large grains, CSS CdS layers must be grown thick enough to minimize the effects of pin-holes. The use of thicker CdS layer causes reduced blue response, resulting in current loss. Therefore, the thickness of CSS CdS window layer must be carefully optimized to achieve high efficiency. Our best small area dot cell using a CSS CdS window layer has exhibited a cell efficiency of about 14.2 % with an open circuit voltage (V
OC
) of 806 mV, a short circuit current (J
SC
) of 25.2 mA/cm
2
, and a fill factor (FF) of 69.8 % under AM1.5 illumination and without an antireflection coating, slightly lower than our best reference cell using a sputtered CdS window layer (V
OC
= 845 mV, J
SC
= 24.5 mA/cm
2
, FF = 76.8 %, and efficiency = 15.8 %).
Antimony selenide (Sb2Se3) is a promising low-cost photovoltaic material with a 1D crystal structure. The grain orientation and defect passivation play a critical role in determining the performance ...of polycrystalline Sb2Se3 thin-film solar cells. In this work, a seed layer is introduced on a molybdenum (Mo) substrate to template the growth of a vertically oriented, columnar Sb2Se3 absorber layer by closed space sublimation. By controlling the grain orientation and compactness of the Sb2Se3 seeds, obtain high-quality Sb2Se3 absorber layers with passive Sb2Se3/Mo interfaces is obtained, which in turn improve the transport of photoexcited charge carriers through the absorber layer and its interfaces. Post-deposition annealing of absorber layers in ambient air is further utilized to passivate the defects in Sb2Se3 and enhance the quality of the front heterojunction. As a result of systematic processing optimization, Sb2Se3 planar heterojunction solar cells are fabricated in substrate configuration with a champion power conversion efficiency of 8.5%.
The development of a scalable chemical bath deposition (CBD) process facilitates the realization of electron-transporting layers (ETLs) for large-area perovskite solar modules (PSMs). Herein, a ...method to prepare a uniform and scalable thick Zn2SnO4 ETL by CBD, which yielded high-performance PSMs, is reported. This Zn2SnO4 ETL exhibits excellent electrical properties and enhanced optical transmittance in the visible region. Moreover, the Zn2SnO4 ETL influences the perovskite layer formation, yielding enhanced crystallinity, increased grain size, and a smoother surface, thus facilitating electron extraction and collection from the perovskite to the ETL. Zn2SnO4 thereby yields PSMs with a remarkable photovoltaic performance, low hysteresis index, and high device reproducibility. The champion PSM exhibited a power conversion efficiency (PCE) of 22.59%, being among the highest values published so far. In addition, the CBD Zn2SnO4-based PSMs exhibit high stability, retaining more than 88% of initial efficiency over 1000 h under continuous illumination. This demonstrates that CBD Zn2SnO4 is an appropriate ETL for high-efficiency PSMs and a viable new process for their industrialization.
The open circuit voltage (VOC) deficit in perovskite solar cells (PSCs) is greater in wide bandgap (>1.7 eV) cells than in ~1.5 eV perovskites. Quasi-Fermi level splitting (QFLS) measurements reveal ...VOC-limiting recombination at the electron transport layer (ETL) contact. This, we find, stems from inhomogeneous surface potential and poor perovskite-ETL energetic alignment. Common monoammonium surface treatments fail to address this; instead we introduce diammonium molecules to modify the perovskite surface states and achieve a more uniform spatial distribution of surface potential. Using 1,3-propane diammonium (PDA), QFLS increases by 90 meV, enabling 1.79 eV PSCs with a certified 1.33 V VOC, and > 19% power conversion efficiency (PCE). Incorporating this layer into a monolithic all-perovskite tandem, we report a record VOC of 2.19 V (89% of the Detailed Balance VOC limit) and > 27% PCE (26.3% certified quasi-steady-state). Furthermore, these tandems retain more than 86% of their initial PCE after 500 hrs operation.
Solar cells are essentially minority carrier devices, and it is therefore of central importance to understand the pertinent carrier transport processes. Here, we advanced a transport imaging ...technique to directly visualize the charge motion and collection in the direction of relevant carrier transport and to understand the cell operation and degradation in state-of-the-art cadmium telluride solar cells. We revealed complex carrier transport profiles in the inhomogeneous polycrystalline thin-film solar cell, with the influence of electric junction, interface, recombination, and material composition. The pristine cell showed a unique dual peak in the carrier transport light intensity decay profile, and the dual peak feature disappeared on a degraded cell after light and heat stressing in the lab. The experiments, together with device modeling, suggested that selenium diffusion plays an important role in carrier transport. The work opens a new forum by which to understand the carrier transport and bridge the gap between atomic/nanometer-scale chemical/structural and submicrometer optoelectronic knowledge.
In traditional optoelectronic approaches, control over spin, charge, and light requires the use of both electrical and magnetic fields. In a spin-polarized light-emitting diode (spin-LED), charges ...are injected, and circularly polarized light is emitted from spin-polarized carrier pairs. Typically, the injection of carriers occurs with the application of an electric field, whereas spin polarization can be achieved using an applied magnetic field or polarized ferromagnetic contacts. We used chiral-induced spin selectivity (CISS) to produce spin-polarized carriers and demonstrate a spin-LED that operates at room temperature without magnetic fields or ferromagnetic contacts. The CISS layer consists of oriented, self-assembled small chiral molecules within a layered organic-inorganic metal-halide hybrid semiconductor framework. The spin-LED achieves ±2.6% circularly polarized electroluminescence at room temperature.
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