Tin halide perovskites attract incremental attention to deliver lead‐free perovskite solar cells. Nevertheless, disordered crystal growth and low defect formation energy, related to Sn(II) oxidation ...to Sn(IV), limit the efficiency and stability of solar cells. Engineering the processing from perovskite precursor solution preparation to film crystallization is crucial to tackle these issues and enable the full photovoltaic potential of tin halide perovskites. Herein, the ionic liquid n‐butylammonium acetate (BAAc) is used to tune the tin coordination with specific O…Sn chelating bonds and NH…X hydrogen bonds. The coordination between BAAc and tin enables modulation of the crystallization of the perovskite in a thin film. The resulting BAAc‐containing perovskite films are more compact and have a preferential crystal orientation. Moreover, a lower amount of Sn(IV) and related chemical defects are found for the BAAc‐containing perovskites. Tin halide perovskite solar cells processed with BAAc show a power conversion efficiency of over 10%. This value is retained after storing the devices for over 1000 h in nitrogen. This work paves the way toward a more controlled tin‐based perovskite crystallization for stable and efficient lead‐free perovskite photovoltaics.
The synergistic strategy of tuning the solution coordination and crystallization process by introducing ionic liquid is implemented to successfully fabricate pinhole‐free tin perovskite films with preferential crystal orientation, which possess improved oxidation repellency for Sn(II) and enhanced hydrophobicity. As a result, the stabilization of high‐efficiency lead‐free tin halide perovskite solar cells is achieved.
Organic–inorganic metal halide perovskite solar cells have emerged in the past few years to promise highly efficient photovoltaic devices at low costs. Here, temperature‐sensitive core–shell Ag@TiO2 ...nanoparticles are successfully incorporated into perovskite solar cells through a low‐temperature processing route, boosting the measured device efficiencies up to 16.3%. Experimental evidence is shown and a theoretical model is developed which predicts that the presence of highly polarizable nanoparticles enhances the radiative decay of excitons and increases the reabsorption of emitted radiation, representing a novel photon recycling scheme. The work elucidates the complicated subtle interactions between light and matter in plasmonic photovoltaic composites. Photonic and plasmonic schemes such as this may help to move highly efficient perovskite solar cells closer to the theoretical limiting efficiencies.
Adding plasmonic core–shell nanoparticles (Ag@TiO2) to perovskite solar cells is shown to improve the photocurrent and thus the overall efficiency. A theoretical model, introducing a novel photon recycling scheme, predicts that highly polarizable nanoparticles act as antennas for light re‐emitted from radiative recombination. The work elucidates the complicated, subtle interactions between light and matter in plasmonic photovoltaic composites.
To date, there have been a plethora of reports on different means to fabricate organic-inorganic metal halide perovskite thin films; however, the inorganic starting materials have been limited to ...halide-based anions. Here we study the role of the anions in the perovskite solution and their influence upon perovskite crystal growth, film formation and device performance. We find that by using a non-halide lead source (lead acetate) instead of lead chloride or iodide, the perovskite crystal growth is much faster, which allows us to obtain ultrasmooth and almost pinhole-free perovskite films by a simple one-step solution coating with only a few minutes annealing. This synthesis leads to improved device performance in planar heterojunction architectures and answers a critical question as to the role of the anion and excess organic component during crystallization. Our work paves the way to tune the crystal growth kinetics by simple chemistry.
We demonstrate the transition from isolated to collective optical modes in plasmonic oligomers. Specifically, we investigate the resonant behavior of planar plasmonic hexamers and heptamers with ...gradually decreasing the interparticle gap separation. A pronounced Fano resonance is observed in the plasmonic heptamer for separations smaller than 60 nm. The spectral characteristics change drastically upon removal of the central nanoparticle. Our work paves the road toward complex hierarchical plasmonic oligmers with tailored optical properties.
Mixed ion perovskite solar cells (PSC) are manufactured with a metal‐free hole contact based on press‐transferred single‐walled carbon nanotube (SWCNT) film infiltrated with ...2,2,7,‐7‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,90‐spirobifluorene (Spiro‐OMeTAD). By means of maximum power point tracking, their stabilities are compared with those of standard PSCs employing spin‐coated Spiro‐OMeTAD and a thermally evaporated Au back contact, under full 1 sun illumination, at 60 °C, and in a N2 atmosphere. During the 140 h experiment, the solar cells with the Au electrode experience a dramatic, irreversible efficiency loss, rendering them effectively nonoperational, whereas the SWCNT‐contacted devices show only a small linear efficiency loss with an extrapolated lifetime of 580 h.
A perovskite solar cell with carbon nanotube‐based hole contact and drop cast 2,2,7,7‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,90‐spirobifluorene (Spiro‐OMeTAD) exhibits superior stability over the standard device with spin‐coated Spiro‐OMeTAD and evaporated gold contact. The solar cells are subjected to a 140 h maximum power point tracking stability experiment in 1 sun illumination and 60 °C, and the carbon‐based cell outperforms the gold cell clearly.
The highest efficiencies in solution-processable perovskite-based solar cells have been achieved using an electron collection layer that requires sintering at 500 °C. This is unfavorable for low-cost ...production, applications on plastic substrates, and multijunction device architectures. Here we report a low-cost, solution-based deposition procedure utilizing nanocomposites of graphene and TiO2 nanoparticles as the electron collection layers in meso-superstructured perovskite solar cells. The graphene nanoflakes provide superior charge-collection in the nanocomposites, enabling the entire device to be fabricated at temperatures no higher than 150 °C. These solar cells show remarkable photovoltaic performance with a power conversion efficiency up to 15.6%. This work demonstrates that graphene/metal oxide nanocomposites have the potential to contribute significantly toward the development of low-cost solar cells.
Structure control in solution-processed hybrid perovskites is crucial to design and fabricate highly efficient solar cells. Here, we utilize in situ grazing incidence wide-angle X-ray scattering and ...scanning electron microscopy to investigate the structural evolution and film morphologies of methylammonium lead tri-iodide/chloride (CH3NH3PbI3–x Cl x ) in mesoporous block copolymer derived alumina superstructures during thermal annealing. We show the CH3NH3PbI3–x Cl x material evolution to be characterized by three distinct structures: a crystalline precursor structure not described previously, a 3D perovskite structure, and a mixture of compounds resulting from degradation. Finally, we demonstrate how understanding the processing parameters provides the foundation needed for optimal perovskite film morphology and coverage, leading to enhanced block copolymer-directed perovskite solar cell performance.
Ionic liquids can retard the perovskite crystallization with the aim to form compact films with larger and more uniformly distributed grain size. The ionic liquid driven crystallization is exploited ...to prepared a record planar perovskite solar cell with stabilized power output of 19.5%.
Organic–inorganic lead halide perovskites have emerged as very promising semiconductors with efficiencies exceeding 22% making them a serious candidate for next generation solar cells. All current ...high performance perovskite solar cells (PSCs), including the most recent world records, were achieved using the so-called anti-solvent method. Here, an anti-solvent, typically chlorobenzene (CB), is used to induce rapid crystallisation of a liquid perovskite precursor resulting in highly homogenous, pinhole-free planar perovskite films. While this has yielded very impressive high-performance results, few efforts have been dedicated to the fundamental understanding of the anti-solvent method. In this work, a systematic study is employed to understand the influence of anti-solvent treatment on both morphological and optoelectronic characteristics of PSCs. Perovskite absorber films were treated using CB and isopropanol (IPA) for comparing anti-solvents with different polarities. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) show that IPA treated perovskite films have a more uniform morphology with larger grains in comparison to CB processed perovskite films. Despite the improved morphology and solar cell performance the devices with IPA treated perovskites suffer from higher hysteresis during current density–voltage ( J – V ) scans. We found that this enhanced hysteresis stems mainly from higher charge accumulation at the TiO 2 /perovskite interface under illumination that could also lead to formation of excess electrostatic potential contributing to an increased open circuit voltage ( V oc ). Our study provides a way for in-depth spectroscopic analysis methods aiding a deeper understanding of the interfacial charge characteristics and the fundamental mechanisms of PSCs.
We investigate the thermally induced morphological and crystalline development of methylammonium lead mixed halide perovskite (CH3NH3PbI3–x Cl x ) thin films and photovoltaic device performance with ...meso-superstructured and planar heterojunction architectures. We observe that a short rapid thermal annealing at 130 °C leads to the growth of large micron-sized textured perovskite domains and improved the short circuit currents and power conversion efficiencies up to 13.5% for the planar heterojunction perovskite solar cells. This work highlights the criticality of controlling the thin film crystallization mechanism of hybrid perovskite materials for high-performing photovoltaic applications.
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