Ruddlesden-Popper Perovskite Nanocrystals as Interface Modification Layer for Efficient Perovskite Solar Cells.

Perovskite nanocrystals are advantageous for interfacial passivation of perovskite solar cells (PSCs), but the insulating long alkyl chain surface ligands impede the charge transfer, while the conventional ligand exchange would possibly introduce surface defects to the nanocrystals. In this work, we reported novel in situ modification of CsPbBr nanocrystals using a short chain conjugated molecule 2-methoxyphenylethylammonium iodide (2-MeO-PEAI) for interfacial passivation of PSCs. Transmission electron microscopy studies with atomic resolution unveil the transformation from cubic CsPbBr to Ruddlesden-Popper phase (RPP) nanocrystals due to halogen exchange.

Breaking the bottleneck of lead-free perovskite solar cells through dimensionality modulation.

The emerging perovskite solar cell (PSC) technology has attracted significant attention due to its superior power conversion efficiency (PCE) among the thin-film photovoltaic technologies. However, the toxicity of lead and poor stability of lead halide materials hinder their commercialization. In this case, after a decade of effort, various categories of lead-free perovskites and perovskite-like materials have been developed, including tin halide perovskites, double perovskites, defect-structured perovskites, and rudorffites.

Separating Crystal Growth from Nucleation Enables the In Situ Controllable Synthesis of Nanocrystals for Efficient Perovskite Light-Emitting Diodes.

Colloidal perovskite nanocrystals (PNCs) display bright luminescence for light-emitting diode (LED) applications; however, they require post-synthesis ligand exchange that may cause surface degradation and defect formation. In situ-formed PNCs achieve improved surface passivation using a straightforward synthetic approach, but their LED performance at the green wavelength is not yet comparable with that of colloidal PNC devices. Here, it is found that the limitations of in situ-formed PNCs stem from uncontrolled formation kinetics: conventional surface ligands confine perovskite nuclei but fail to delay crystal growth.

In-plane stimulated emission of polycrystalline CHNHPbBr perovskite thin films.

Hybrid organic-inorganic lead halide perovskites have been investigated extensively within the last decades, for its great potential in efficient solar cells and as an ideal light source. Among the studies on stimulated emission (SE), the emission is either out-of-plane for polycrystalline films or in-plane with randomly aligned single microcrystals and nanowires. In this work, we revealed in-plane propagation of SE from bromine-based perovskite polycrystalline thin films (CHNHPbBr, or MAPbBr).

Exciton and bi-exciton mechanisms in amplified spontaneous emission from CsPbBr perovskite thin films.

We studied temperature-dependent amplified spontaneous emission (ASE) in CsPbBr perovskite thin films. For temperatures 180-360 K, a narrow-band lasing is observed. However, a new accompanying ASE band appears below 180 K, indicating a more complicated behavior.

Investigation on binding energy and reduced effective mass of exciton in organic-inorganic hybrid lead perovskite films by a pure optical method.

The exciton binding energy and its reduced effective mass in hybrid lead perovskite, which play a key role in the process of excitons forming, largely determine the excellent optical properties of the perovskite materials and hence, the device performance. We introduce the systematic measurements on these two parameters of the organic-inorganic hybrid perovskite films of (MA/FA)Pb(Br/I) by a unique temperature and density-resolved optical spectroscopic method. The method is simple and straightforward, since it directly observes the exciton ionization and recombination.

To Greatly Reduce Defects via Photoannealing for High-Quality Perovskite Films.

The performance of perovskite solar cells (PSCs) depends on the crystallization of the perovskite layer. Herein, we demonstrate an effective photoannealing (PA) process by a halogen lamp. During the PA process, on the one hand, the lower energy photon, that is, near IR up to ∼1015 nm photon, drives the crystallization of the perovskite film, similar to the conventional thermal annealing (TA).

Efficient and Stable Perovskite Solar Cell with High Open-Circuit Voltage by Dimensional Interface Modification.

High-efficiency organic-inorganic hybrid perovskite solar cells have experienced rapid development and attracted significant attention in recent years. However, instability to an ambient environment such as moisture is a facile challenge for the application of perovskite solar cells. Herein, 1,8-octanediammonium iodide (ODAI) is employed to construct a two-dimensional modified interface by in situ combined with residual PbI on the formamidinium lead iodide (FAPbI) perovskite surface.

Solution-Processed CuS as a Hole Transport Layer for Efficient and Stable Perovskite Solar Cells.

Organic-inorganic perovskite solar cells have seen tremendous developments in recent years. As a hole transport material, 2,2',7,7'-tetrakis( N, N-di- p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD) is widely used in n-i-p perovskite solar cells. However, it may lead to the perovskite film degradation due to the dopant lithium bis((trifluoromethyl)sulfonyl)amide (Li-TFSI), which has strong hydrophilicity.

The Dawn of Lead-Free Perovskite Solar Cell: Highly Stable Double Perovskite CsAgBiBr Film.

Recently, lead-free double perovskites have emerged as a promising environmentally friendly photovoltaic material for their intrinsic thermodynamic stability, appropriate bandgaps, small carrier effective masses, and low exciton binding energies. However, currently no solar cell based on these double perovskites has been reported, due to the challenge in film processing. Herein, a first lead-free double perovskite planar heterojunction solar cell with a high quality CsAgBiBr film, fabricated by low-pressure assisted solution processing under ambient conditions, is reported.

Ion Implantation-Modified Fluorine-Doped Tin Oxide by Zirconium with Continuously Tunable Work Function and Its Application in Perovskite Solar Cells.

In recent years, perovskite solar cells have drawn a widespread attention. As an electrode material, fluorine-doped tin oxide (FTO) is widely used in various kinds of solar cells. However, the relatively low work function (WF) (∼4.

High Crystallization of Perovskite Film by a Fast Electric Current Annealing Process.

High-efficiency organic-inorganic hybrid perovskite solar cells have experienced rapid development and attracted significant attention in recent years. Crystal growth as an important factor would significantly influence the quality of perovskite films and ultimately the device performance, which usually requires thermal annealing for 10 min or more. Herein, we demonstrate a new method to get high crystallization of perovskite film by electric current annealing for just 5 s.

High-Performance Self-powered Photodetectors Based on ZnO/ZnS Core-Shell Nanorod Arrays.

In recent years, there is an urgent demand for high-performance ultraviolet photodetectors with high photosensitivity, fast responsivity, and excellent spectral selectivity. In this letter, we report a self-powered photoelectrochemical cell-type UV detector using the ZnO/ZnS core-shell nanorod array as the active photoanode and deionized water as the electrolyte. This photodetector demonstrates an excellent spectral selectivity and a rapid photoresponse time of about 0.

ZnO nanosheet arrays constructed on weaved titanium wire for CdS-sensitized solar cells.

Ordered ZnO nanosheet arrays were grown on weaved titanium wires by a low-temperature hydrothermal method. CdS nanoparticles were deposited onto the ZnO nanosheet arrays using the successive ionic layer adsorption and reaction method to make a photoanode. Nanoparticle-sensitized solar cells were assembled using these CdS/ZnO nanostructured photoanodes, and their photovoltaic performance was studied systematically.

CdS quantum dot-sensitized solar cells based on nano-branched TiO2 arrays.

Nano-branched rutile TiO2 nanorod arrays were grown on F:SnO2 conductive glass (FTO) by a facile, two-step wet chemical synthesis process at low temperature. The length of the nanobranches was tailored by controlling the growth time, after which CdS quantum dots were deposited on the nano-branched TiO2 arrays using the successive ionic layer adsorption and reaction method to make a photoanode for quantum dot-sensitized solar cells (QDSCs). The photovoltaic properties of the CdS-sensitized nano-branched TiO2 solar cells were studied systematically.