Metal halides perovskites, such as hybrid organic–inorganic CH3NH3PbI3, are newcomer optoelectronic materials that have attracted enormous attention as solution-deposited absorbing layers in solar cells with power conversion efficiencies reaching 20%. Herein we demonstrate a new avenue for halide perovskites by designing highly luminescent perovskite-based colloidal quantum dot materials. We have synthesized monodisperse colloidal nanocubes (4–15 nm edge lengths) of fully inorganic cesium lead halide perovskites (CsPbX3, X = Cl, Br, and I or mixed halide systems Cl/Br and Br/I) using inexpensive commercial precursors. Through compositional modulations and quantum size-effects, the bandgap energies and emission spectra are readily tunable over the entire visible spectral region of 410–700 nm. The photoluminescence of CsPbX3 nanocrystals is characterized by narrow emission line-widths of 12–42 nm, wide color gamut covering up to 140% of the NTSC color standard, high quantum yields of up to 90%, and radiativ...

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Nanocrystals of Cesium Lead Halide Perovskites (CsPbX3, X = Cl, Br, and I): Novel Optoelectronic Materials Showing Bright Emission with Wide Color Gamut

Advancing perovskite solar cell technologies toward their theoretical power conversion efficiency (PCE) requires delicate control over the carrier dynamics throughout the entire device. By controlling the formation of the perovskite layer and careful choices of other materials, we suppressed carrier recombination in the absorber, facilitated carrier injection into the carrier transport layers, and maintained good carrier extraction at the electrodes. When measured via reverse bias scan, cell PCE is typically boosted to 16.6% on average, with the highest efficiency of ~19.3% in a planar geometry without antireflective coating. The fabrication of our perovskite solar cells was conducted in air and from solution at low temperatures, which should simplify manufacturing of large-area perovskite devices that are inexpensive and perform at high levels.

http://science.sciencemag.org/content/sci/345/6196/542.full.pdf

Interface engineering of highly efficient perovskite solar cells

The performance of solar cells based on organic–inorganic perovskites strongly depends on the device architecture and processing conditions. It is now shown that solvent engineering enables the deposition of very dense perovskite layers on mesoporous titania, leading to photovoltaic devices with a high light-conversion efficiency and no hysteresis.

Solvent engineering for high-performance inorganic–organic hybrid perovskite solar cells

Within the space of a few years, hybrid organic–inorganic perovskite solar cells have emerged as one of the most exciting material platforms in the photovoltaic sector. This review describes the rapid progress that has been made in this area.

The emergence of perovskite solar cells

The band gap of formamidinium lead iodide (FAPbI3) perovskites allows broader absorption of the solar spectrum relative to conventional methylammonium lead iodide (MAPbI3). Because the optoelectronic properties of perovskite films are closely related to film quality, deposition of dense and uniform films is crucial for fabricating high-performance perovskite solar cells (PSCs). We report an approach for depositing high-quality FAPbI3 films, involving FAPbI3 crystallization by the direct intramolecular exchange of dimethylsulfoxide (DMSO) molecules intercalated in PbI2 with formamidinium iodide. This process produces FAPbI3 films with (111)-preferred crystallographic orientation, large-grained dense microstructures, and flat surfaces without residual PbI2. Using films prepared by this technique, we fabricated FAPbI3-based PSCs with maximum power conversion efficiency greater than 20%.

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High-performance photovoltaic perovskite layers fabricated through intramolecular exchange

Halide perovskites have received attention in the field of photocatalysis owing to their excellent optoelectronic properties. However, the semiconductor properties of halide perovskite surfaces and the influence on photocatalytic performance have not been systematically clarified. Now, the conversion of triose (such as 1,3-dihydroxyacetone (DHA)) is employed as a model reaction to explore the surface termination of MAPbI3 . By rational design of the surface termination for MAPbI3 , the production rate of butyl lactate is substantially improved to 7719 μg g-1  cat. h-1 under visible-light illumination. The MAI-terminated MAPbI3 surface governs the photocatalytic performance. Specially, MAI-terminated surface is susceptible to iodide oxidation, which thus promotes the exposure of PbII as active sites for this photocatalysis process. Moreover, MAI-termination induces a p-doping effect near the surface for MAPbI3 , which facilitates carrier transport and thus photosynthesis.

The Role of Surface Termination in Halide Perovskites for Efficient Photocatalytic Synthesis

We design and synthesize an amino-functionalized conjugated polymer (PPDI-F3N) based on perylene diimide and use it as a multifunctional interfacial layer of TiO2/perovskite in conventional planar perovskite solar cells. The work function of TiO2 is modulated by PPDI-F3N to better align with the conduction band of the perovskite, leading to efficient charge extraction. PPDI-F3N can passivate the TiO2 surface to reduce the severe recombination loss and rapid degradation caused by oxygen vacancies on the UV-sensitive TiO2 surface. Moreover, modulated polarity of PPDI-F3N is beneficial to optimal perovskite crystallization and morphology. All these features contribute to a higher efficiency (18.3%) of the PSCs with the PPDI-F3N interlayer relative to the control devices without the interlayer (16.7%) as well as improved stability and a reduced hysteresis effect.

An amino-substituted perylene diimide polymer for conventional perovskite solar cells

We report an approach for the fabrication of CuIn(S,Se)2-based photovoltaic devices from hydrazinium precursors in non-hydrazine solvents, specifically a ethanolamine/dimethyl sulfoxide (EA/DMSO) mixture. For the first time, both Cu hydrazinium precursor and Cu-In hydrazinium precursor are found with good solubility in non-hydrazine solvents, producing molecular-level blending of metal precursors. Sulfur loss in Cu hydrazinium precursor is compensated for by either introduction of excessive S/Se or the formation of S/Se-bridged Cu-In compounds. The success of dissolving Cu-In hydrazinium precursor is ascribed to the coordinated S group and strong intramolecular interaction within non-hydrazine solvents. X-ray diffraction (XRD) and Raman characterization indicate the formation of the CuIn(S,Se)2 phase after annealing. Through introducing different amounts of excess S/Se, the ratio between CuInS2 and CuInSe2, as well as the morphology of the resulted CuIn(S,Se)2 film can be controlled. Optimized devices exhibit a power conversion efficiency of 3.8% with a CISS absorber layer of only around 300 nm thickness, which is comparable to N2H4-based devices of similar thickness.

Non‐Hydrazine Solutions in Processing CuIn(S,Se)2 Photovoltaic Devices from Hydrazinium Precursors

According to some embodiments of the present invention, a method of producing an organic-inorganic perovskite thin film includes depositing a layer of inorganic material on a substrate to form an inorganic film, and performing an organic vapor treatment of the inorganic film to produce an organic-inorganic perovskite thin film. The layer of inorganic material comprises an inorganic anion layer having a metal-ligand framework, and the organic vapor treatment provides organic cations capable of becoming inserted into the metal-ligand framework of the inorganic anion layer to form a perovskite structure.

Huanping Zhou

Papers

The Role of Surface Termination in Halide Perovskites for Efficient Photocatalytic Synthesis

An amino-substituted perylene diimide polymer for conventional perovskite solar cells

Non‐Hydrazine Solutions in Processing CuIn(S,Se)2 Photovoltaic Devices from Hydrazinium Precursors

Sequential processing with vapor treatment of thin films of organic-inorganic perovskite materials

Insights into Large‐Scale Fabrication Methods in Perovskite Photovoltaics