Lead halide perovskite solar cells now show excellent efficiencies and encouraging levels of stability. Further improvements in performance require better control of the trap states which are ...considered to be associated with vacancies and defects at crystallite surfaces. Herein, a reflection on the ways in which these traps can be mitigated is presented by improving the quality of the perovskite layer and interfaces in fully assembled device configurations. In this review, the most recent design strategies reported in the literature, which have been explored to tune grain orientation, to passivate defects, and to improve charge‐carrier lifetimes, are presented. Specifically, the advances made with single‐cation, mixed‐cation and/or mixed‐halide, and 3D/2D bilayer‐based light absorbers are discussed. The interfacial, compositional, and band alignment engineering along with their consequent effects on the open‐circuit voltage, power conversion efficiency, and stability are a particular focus.
Despite the record efficiency exceeding 25%, the long‐term operational stability of perovskite solar cells is limited by the degradation mechanisms accelerated by the presence of vacancies and defects. In this review, recent engineering strategies ranging from grains to interfaces that mitigate degradation and improve efficiencies are discussed.
TiO2 nanotube arrays prepared by electrochemical anodization of Ti foils show impressive light to electricity conversion efficiency in the dye-sensitized solar cells (DSCs). The length of the TiO2 ...nanotube arrays (5−14 µm) was controlled by varying the anodization time from 2 to 20 h. The influence of nanotube lengths on the photovoltaic performance of DSCs was investigated by impedance. A flexible DSC using TiO2 nanotube arrays on a Ti foil as a working electrode and polyethylene naphthalate (ITO/PEN) as counterelectrode in combination with solvent-free ionic liquid electrolyte achieved 3.6% photovoltaic conversion efficiency under simulated AM 1.5 sunlight.
Hybrid (organic-inorganic) multication lead halide perovskites hold promise for a new generation of easily processable solar cells. Best performing compositions to date are multiple-cation solid ...alloys of formamidinium (FA), methylammonium (MA), cesium, and rubidium lead halides which provide power conversion efficiencies up to around 22%. Here, we elucidate the atomic-level nature of Cs and Rb incorporation into the perovskite lattice of FA-based materials. We use 133Cs, 87Rb, 39K, 13C, and 14N solid-state MAS NMR to probe microscopic composition of Cs-, Rb-, K-, MA-, and FA-containing phases in double-, triple-, and quadruple-cation lead halides in bulk and in a thin film. Contrary to previous reports, we have found no proof of Rb or K incorporation into the 3D perovskite lattice in these systems. We also show that the structure of bulk mechanochemical perovskites bears close resemblance to that of thin films, making them a good benchmark for structural studies. These findings provide fundamental understanding of previously reported excellent photovoltaic parameters in these systems and their superior stability.
Dye-sensitized solar cells (DSCs) convert light into electricity by using photosensitizers adsorbed on the surface of nanocrystalline mesoporous titanium dioxide (TiO
) films along with electrolytes ...or solid charge-transport materials
. They possess many features including transparency, multicolour and low-cost fabrication, and are being deployed in glass facades, skylights and greenhouses
. Recent development of sensitizers
, redox mediators
and device structures
has improved the performance of DSCs, particularly under ambient light conditions
. To further enhance their efficiency, it is pivotal to control the assembly of dye molecules on the surface of TiO
to favour charge generation. Here we report a route of pre-adsorbing a monolayer of a hydroxamic acid derivative on the surface of TiO
to improve the dye molecular packing and photovoltaic performance of two newly designed co-adsorbed sensitizers that harvest light quantitatively across the entire visible domain. The best performing cosensitized solar cells exhibited a power conversion efficiency of 15.2% (which has been independently confirmed) under a standard air mass of 1.5 global simulated sunlight, and showed long-term operational stability (500 h). Devices with a larger active area of 2.8 cm
exhibited a power conversion efficiency of 28.4% to 30.2% over a wide range of ambient light intensities, along with high stability. Our findings pave the way for facile access to high-performance DSCs and offer promising prospects for applications as power supplies and battery replacements for low-power electronic devices
that use ambient light as their energy source.
To dye for: A porphyrin chromophore, which is integrated into a donor–acceptor dye as a π‐conjugated bridge (see picture), exhibits an unprecedented efficiency of 11 % when used as a photosensitizer ...in a double‐layer TiO2 film. A greatly enhanced photovoltaic performance is observed when the porphyrin dye is cosensitized with a metal‐free dye that has a complementary spectral response.
Mixed-cation organic lead halide perovskites attract unfaltering attention owing to their excellent photovoltaic properties. Currently, the best performing perovskite materials contain multiple ...cations and provide power conversion efficiencies up to around 22%. Here, we report the first quantitative, cation-specific data on cation reorientation dynamics in hybrid mixed-cation formamidinium (FA)/methylammonium (MA) lead halide perovskites. We use 14N, 2H, 13C, and 1H solid-state MAS NMR to elucidate cation reorientation dynamics, microscopic phase composition, and the MA/FA ratio, in (MA)x(FA)1-xPbI3 between 100 and 330 K. The reorientation rates correlate in a striking manner with the carrier lifetimes previously reported for these materials and provide evidence of the polaronic nature of charge carriers in PV perovskites.
A stable dye-sensitized solar cell has been obtained based on a new binary ionic liquid electrolyte system containing 1-propyl-3-methylimidazolium iodide and 1-ethyl-3-methylimidazolium ...tetracyanoborate.
Today's best perovskite solar cells use a mixture of formamidinium and methylammonium as the monovalent cations. With the addition of inorganic cesium, the resulting triple cation perovskite ...compositions are thermally more stable, contain less phase impurities and are less sensitive to processing conditions. This enables more reproducible device performances to reach a stabilized power output of 21.1% and ∼18% after 250 hours under operational conditions. These properties are key for the industrialization of perovskite photovoltaics.
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