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.