skip to main content


Title: Enhanced Nucleation of Atomic Layer Deposited Contacts Improves Operational Stability of Perovskite Solar Cells in Air
Abstract

Metal‐halide perovskites show promise as highly efficient solar cells, light‐emitting diodes, and other optoelectronic devices. Ensuring long‐term stability is now a major priority. In this study, an ultrathin (2 nm) layer of polyethylenimine ethoxylated (PEIE) is used to functionalize the surface of C60for the subsequent deposition of atomic layer deposition (ALD) SnO2, a commonly used electron contact bilayer for p–i–n devices. The enhanced nucleation results in a more continuous initial ALD SnO2layer that exhibits superior barrier properties, protecting Cs0.25FA0.75Pb(Br0.20I0.80)3films upon direct exposure to high temperatures (200 °C) and water. This surface modification with PEIE translates to more stable solar cells under aggressive testing conditions in air at 60 °C under illumination. This type of “built‐in” barrier layer mitigates degradation pathways not addressed by external encapsulation, such as internal halide or metal diffusion, while maintaining high device efficiency up to 18.5%. This nucleation strategy is also extended to ALD VOxfilms, demonstrating its potential to be broadly applied to other metal oxide contacts and device architectures.

 
more » « less
PAR ID:
10372905
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Advanced Energy Materials
Volume:
9
Issue:
47
ISSN:
1614-6832
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    The hole transport layer (HTL) is one of the key components in planar perovskite solar cells. This study reports a new kind of HTL fabricated using atomic layer deposition (ALD). By alloying TiO2with IrOx, it is demonstrated that TiO2, a well‐known electron‐selective contact and electron transport layer in photovoltaic devices, can behave as an HTL with an appropriately high work function. Perovskite Cs0.17FA0.83Pb(I0.83Br0.17)3solar cells including this new hole transport material achieve a power conversion efficiency of 15.8% under AM 1.5G simulated solar irradiation compared to a 14.3% efficiency for otherwise‐identical devices incorporating a more standard NiO HTL layer. These results suggest the promise of transition metal oxide alloys synthesized by ALD as hole contact materials for optoelectronic devices, including advanced photovoltaics.

     
    more » « less
  2. Abstract

    The practical implementation of Li metal batteries is hindered by difficulties in controlling the Li metal plating microstructure. While previous atomic layer deposition (ALD) studies have focused on directly coating Li metal with thin films for the passivation of the electrode–electrolyte interface, a different approach is adopted, situating the ALD film beneath Li metal and directly on the copper current collector. A mechanistic explanation for this simple strategy of controlling the Li metal plating microstructure using TiO2grown on copper foil by ALD is presented. In contrast to previous studies where ALD‐grown layers act as artificial interphases, this TiO2layer resides at the copper–Li metal interface, acting as a nucleation layer to improve the Li metal plating morphology. Upon lithiation of TiO2, a LixTiO2complex forms; this alloy provides a lithiophilic surface layer that enables uniform and reversible Li plating. The reversibility of lithium deposition is evident from the champion cell (5 nm TiO2), which displays an average Coulombic efficiency (CE) of 96% after 150 cycles at a moderate current density of 1 mA cm−2. This simple approach provides the first account of the mechanism of ALD‐derived Li nucleation control and suggests new possibilities for future ALD‐synthesized nucleation layers.

     
    more » « less
  3. Abstract

    Comprehensive treatment of indoor contaminants such as volatile organic compounds (VOCs) and fine particulate matter (PM2.5) using transition metal oxide catalysts or functional fibrous filters has gained substantial attention recently. However, coupling VOC oxidation catalysts into high‐performance filter systems remains a challenge. Herein, an overall solution to strongly bind manganese dioxide (MnO2) nanocrystals onto polypropylene (PP) nonwoven fabrics is provided. For the first time, uniform heterogeneous nucleation and growth of MnO2onto PP nonwoven fabrics using intermediate inorganic nucleation films, including Al2O3, TiO2, and ZnO, formed conformally on the fabrics via atomic layer deposition (ALD) are demonstrated. How different ALD thin films influence the crystallinity, morphology, surface area, and surface oxygen species of the MnO2grown ALD‐coated PP fibers is further investigated. In addition to uniformity and integrity, ZnO thin films give rise to MnO2crystals with the largest fraction of available surface oxygen, enabling 99.5% catalytic oxidation of formaldehyde within 60 min. Moreover, the metal oxide filters provide excellent PM removal efficiencies (ePM), achievingePM2.590% andePM1098%, respectively, making the approach an outstanding method to produce fully dual‐functional filtration media.

     
    more » « less
  4. To enable greater control over thermal atomic layer deposition (ALD) of molybdenum disulfide (MoS 2 ), here we report studies of the reactions of molybdenum hexafluoride (MoF 6 ) and hydrogen sulfide (H 2 S) with metal oxide substrates from nucleation to few-layer films. In situ quartz crystal microbalance experiments performed at 150, 200, and 250 °C revealed temperature-dependent nucleation behavior of the MoF 6 precursor, which is attributed to variations in surface hydroxyl concentration with temperature. In situ Fourier transform infrared spectroscopy coupled with ex situ x-ray photoelectron spectroscopy (XPS) indicated the presence of molybdenum oxide and molybdenum oxyfluoride species during nucleation. Density functional theory calculations additionally support the formation of these species as well as predicted metal oxide to fluoride conversion. Residual gas analysis revealed reaction by-products, and the combined experimental and computational results provided insights into proposed nucleation surface reactions. With additional ALD cycles, Fourier transform infrared spectroscopy indicated steady film growth after ∼13 cycles at 200 °C. XPS revealed that higher deposition temperatures resulted in a higher fraction of MoS 2 within the films. Deposition temperature was found to play an important role in film morphology with amorphous films obtained at 200 °C and below, while layered films with vertical platelets were observed at 250 °C. These results provide an improved understanding of MoS 2 nucleation, which can guide surface preparation for the deposition of few-layer films and advance MoS 2 toward integration into device manufacturing. 
    more » « less
  5. Abstract

    We fabricate and characterize methylammonium lead halide perovskite film as a novel back contact to CdTe thin‐film solar cells. We apply ~0.75 μm perovskite film at the interface of CdCl2‐activated and Cu‐doped CdTe surface and complete the device with Au back contact. We use Cu/Au back contact as a reference to compare results with novel back contact. Our investigation shows that incorporation of thin layer of perovskite film before the back contact metal reduces back contact barrier effect and improves fill factor (FF) and open‐circuit voltage (VOC) of the solar cells. Our low temperature JV results prove that thin‐film perovskite is a very necessary component in CdTe solar cells to reduce back contact barrier, to minimize interface or surface recombination, to improve collection efficiencies, and to increase the efficiency of solar cells. Our best device shows 7% increase in VOCto 0.875 V and ~7% increase in FF with the highest FF of 81%, and solar cell's efficiency finally increases by 10% with the use of MAPb(I1‐xBrx)3as an interface layer.

     
    more » « less