In this paper, we reported the in situ fabrication of highly luminescent formamidinium lead bromide (FAPbBr) nanocrystal thin films by dropping toluene as an anti-solvent during the spin-coating with a perovskite precursor solution using 3,3-diphenylpropylamine bromide (DPPA-Br) as a ligand. The resulting films are uniform and composed of 5-20 nm FAPbBr perovskite nanocrystals. By monitoring the solvent mixing of anti-solvent and precursor solution on the substrates, we illustrated the difference between the ligand-assisted reprecipitation (LARP) process and the nanocrystal-pinning (NCP) process. This understanding provides a guideline for film optimization, and the optimized films obtained through the in situ LARP process exhibit strong photoluminescence emission at 528 nm, with quantum yields up to 78% and an average photoluminescence lifetime of 12.7 ns. In addition, an exciton binding energy of 57.5 meV was derived from the temperature-dependent photoluminescence measurement. More importantly, we achieved highly efficient pure green perovskite based light-emitting diode (PeLEDs) devices with an average external quantum efficiency (EQE) of 7.3% (maximum EQE is 16.3%) and an average current efficiency (CE) of 29.5 cd A (maximum CE is 66.3 cd A) by adapting a conventional device structure of ITO/PEDOT:PSS/TFB/perovskite film/TPBi/LiF/Al. It is expected that the in situ LARP process provides an effective methodology for the improvement of the performance of PeLEDs.

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This communication describes the use of Ag 2 S-encapsulated Au nanorods (AuNR@Ag 2 S) to enhance longer wavelength sunlight utility in dye-sensitized solar cells (DSSCs). We observed that the longitudinal plasmon resonance of AuNRs induces a remarkable increase of 37.6% in photocurrent generation at 600-720 nm. Optical characterizations indicate that the increased optical density and decreased light transmission as a result of AuNRs incorporation engender the striking improvement. With AuNR@Ag 2 S, the final power conversion efficiency (PCE) of the DSSC with a thin anode (6 mm) increases from 4.3% to 5.6%, which is comparable to that of a pure TiO 2 anode based DSSC (5.8%) with a film thickness of 11 mm. Further, incorporation of AuNR@Ag 2 S into the thick anode leads to the PCE increasing to 7.1%.A dye-sensitized solar cell (DSSC) is composed of an inorganic semiconducting photoanode with adsorbed dye sensitizers and filled by electrolyte, and a platinized counter electrode. 1,2 This device configuration has attracted increasing interest primarily due to its easy fabrication and reasonably high solar-to-electric power conversion efficiency (PCE). [3][4][5][6] Extending the response of dye sensitizers to a broader range of the solar spectrum is a key step in further improving the device efficiency. 1,7 It is estimated that a PCE over 15% using I À /I 3 À as redox couple would require a DSSC absorbing 80% of sunlight from 350 to 900 nm. 8 To date, the most efficient conventional sensitizers are polypyridyl ruthenium dyes with a bandgap of about 1.8 eV, e.g., N3 and N719. Their strong absorption peaked at 530 nm while the absorption coefficient drastically decreased at longer wavelength. 1 Therefore, strategies that can increase the lower energy sunlight harvesting would maximize the usage of the existing dyes, leading to improved device efficiency. A few methods have been performed to extend the absorption spectrum through reorienting thiocyanate ligands, altering bipyridyl ligands, or replacing ruthenium with osmium as central metal. 8 Whereas light-to-electricity conversion at longer wavelengths is improved, the overall efficiency is not increased due to reduced light harvesting efficiency at the original absorption maximum. Other relevant works incorporate energy relay dyes 9 or develop new dye molecules with strong absorption in the red or near-infrared (NIR) region, such as those of indolines, coumarins and squaraines. 8,10-12 Nonetheless, the overall PCEs are usually smaller, sometimes becoming much lower, than those of N3/N719 analogues due to either loss of the strong absorption at 500-600 nm or difficulty in generating appropriate electronic configurations that match well with the semiconducting photoanode and/or tri-iodide electrolyte. 8,12 Apparently, increasing the photocurrent generation at longer wavelength of the conventional N3/N719 without sacrificing the original absorption is highly preferable.A recently developed method to increase light utility in solar cells exploits localized surface plasmon...

In the field of perovskite light-emitting diodes (PeLEDs), the performance of blue emissive electroluminescence devices lags behind the other counterparts due to the lack of fabrication methodology. Herein, we demonstrate the in situ fabrication of CsPbClBr2 nanocrystal films by using mixed ligands of 2-phenylethanamine bromide (PEABr) and 3,3-diphenylpropylamine bromide (DPPABr). PEABr dominates the formation of quasi-two-dimensional perovskites with small-n domains, while DPPABr induces the formation of large-n domains. Strong blue emission at 470 nm with a photoluminescence quantum yield up to 60% was obtained by mixing the two ligands due to the formation of a narrower quantum-well width distribution. Based on such films, efficient blue PeLEDs with a maximum external quantum efficiency of 8.8% were achieved at 473 nm. Furthermore, we illustrate that the use of dual-ligand with respective tendency of forming small-n and large-n domains is a versatile strategy to achieve narrow quantum-well width distribution for photoluminescence enhancement.

A series of simple phenothiazine-based dyes have been synthesized, in which a cyanoacrylate acceptor directly attached to the C(3) position of phenothiazine, and an additional linear electron-rich (4-hexyloxy)phenyl group at C(7) on the opposite side of the acceptor, and an alkyl chain with different length at N(10) of the phenothiazine periphery are presented. The dye molecules have a linear shape which is favorable for the formation of a compact dye layer on the TiO 2 surface, while their butterfly conformations can sufficiently inhibit molecular aggregation. Moreover, the structural features of (4-hexyloxy)phenyl donor moiety at the C(7) position of phenothiazine extends the π-conjugation of the chromophore, thus enhancing the performance of dye-sensitized solar cells (DSSCs). Moreover, the alkyl substituents with different chain length at the N(10) atom of phenothiazine could further optimize the performance through completely shielding the surface of TiO 2 from the I − /I 3electrolyte and subsequently reducing the leakage of dark current. Under simulated AM 1.5G irradiation, the PT-C6 based DSSC produces a short-circuit photocurrent of 15.32 mA cm −2 , an open-circuit photovoltage of 0.78 V, a fill factor of 0.69, corresponding to a power conversion efficiency (PCE) of 8.18%, which exceeds the reference N719 (7.73%) under identical fabrication conditions. Notably, the designed molecular structure represents the highest photovoltaic conversion efficiency value when compared with other reported phenothiazine-derived dyes.

in bulk halide perovskites, long carrier diffusion length, and an absorption range covering the visible solar spectrum, collectively enable the high performance of photo electricity conversion. Compared to the bulk materials, perovskite nanocrystals or quantum dots (usually denoted as PNCs or PQDs) show obvious excitonic features with enhanced photoluminescence (PL) properties due to the well-known size-dependent quantum confinement effects. [14][15][16][17] The combination of color saturated emissions, super high quantum yield (QY), as well as easy processing inspired the intensive exploration of PNCs as light emitters, which is now under spotlights in the field of optical materials.The first perspective aim of PNCs is to alternate the state-of-the-art CdSe or InP quantum dots (QDs) as new generation luminescence materials. [18,19] As shown in Figure 1, these QD materials have been well demonstrated to be potential functional components for photonic and optoelectronic applications, and are currently on the way to industrialization. [20][21][22][23] Specifically, QDs can be employed as fluorescence labels, [24] laser gain media, [25] LED phosphors, [26] and down-shifting films for LCD backlights. [27,28] They can also be processed into thin film for optoelectronic devices including solar cells, [29] photodetectors, [30,31] transistors [32] and LEDs. [33] The PNCs outcompete these conventional QDs in terms of narrower full width at half maximum (FWHM) and low fabrication cost, but most importantly, the ease of in situ preparation. [34,35] Herein, this progress report highlight the developments of in situ fabricated PNCs.Colloidal semiconductor QDs are typically synthesized ex situ in flasks by hot injection method, stabilized by surface ligands. [36][37][38][39] To incorporate such solution based materials into applications usually requires purification, redispersion and surface engineering. For instance, ligand exchange is often employed to disperse QDs into aimed solvent, inducing defects that inevitably derogating the PLQYs. [40] Moreover, the organic ligands themselves also suffer from the risk of disabsorbing, reducing the stability of the QDs and thus the final devices. [41] Because halide perovskite are ionic compounds that can be well dissolved into polar solvents, PNCs can be fabricated through either ex situ routes in flask or in situ strategies on substrates. The in situ fabricated PNCs are adaptable to devices integration due to their scalable and low-cost manufacturing. In this regard, more and more efforts have been made in terms of the controlling synthesis, physical properties and device applications of PNC materials.After over 30 years of development, colloidal quantum dots have now become mature luminescent materials in photonic and optoelectronic operations and start to hit the market. The emerging perovskite nanocrystals are expected to promote large-scale commercialization due to their superior optical properties as well as low cost and easy fabrication. This progress report is focused on the...

We report the room temperature template synthesis of CuInS 2 nanocrystals through incorporation of Cu + cations into In 2 S 3 nanoplates whose chemical composition has been controlled by varying the amount of copper ions in the reaction mixture. As a result, bandgaps of the resultant CuInS 2 nanoplates can be tuned from 1.45 to 1.19 eV with [Cu]/[In] molar ratios increasing from 0.7 to 2.9, which was demonstrated by the cyclic voltammetry. We explored the use of CuInS 2 nanocrystals as potential counter electrode in dye-sensitized solar cells and a power conversion efficiency of 6.83 % was achieved without selenization and ligand exchange. The value is comparable with the performance of control device using a Pt as counter electrode (power conversion efficiency: 7.08 %) under the same device architecture. IntroductionTernary and quaternary semiconductor nanocrystals (NCs) (e.g., CuInS 2 , CuInSe 2 , CuInGaS 2 , CuZnSnS 4 ) with advantages of tunable bandgaps and more environmentally friendly constituents have been receiving great attentions for solar-harvesting and light-emitting applications, in particular for solution-processed devices. 1-17 For example, CuInS 2 NCs are regarded as promising candidates as light absorber or counter electrode (CE) in dye-sensitized solar cells (DSSCs), due to the advantage of low cost and simple fabrication process. 18-23 Because the electronic structure of these materials strongly correlate with the [Cu]/[In] ratios, there is a great need to precisely control their size, shape, surface and compositions. 3,19,24,25 Although great success has been made in synthesis of ternary and quaternary NCs, providing several routes including thermal decomposition of single precursors, 26-30 solvothermal synthesis approach, 31-33 hot-injection 4,5,34-36 and non-injection methods, 7, 37-41 the different reactivity of metallic cation precursors often leads to a poor stoichiometric control and the formation of intermediate products such as biphasic nanomaterials and heterostructures. [42][43][44][45] To overcome such drawbacks of the composition control,

An ethylenediamine-grafted Y zeolite effectively adsorbs CO2 from a wet flue gas and it is highly regenerable through a temperature swing adsorption (TSA) process.