Long-term durability is critically important for the commercialization of perovskite solar cells (PSCs). The ionic character of the perovskite and the hydrophilicity of commonly used additives for the hole-transporting layer (HTL), such as lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) and tertbutylpyridine (tBP), render PSCs prone to moisture attack, compromising their long-term stability. Here we introduce a trifluoromethylation strategy to overcome this drawback and to boost the PSC's solar to electric power conversion efficiency (PCE). We employ 4-(trifluoromethyl)benzylammonium iodide (TFMBAI) as an amphiphilic modifier for interfacial defect mitigation and 4-(trifluoromethyl)pyridine (TFP) as an additive to enhance the HTL's hydrophobicity. Surface treatment of the triple-cation perovskite with TFMBAI largely suppressed the nonradiative charge carrier recombination, boosting the PCE from 20.9% to 23.9% and suppressing hysteresis, while adding TFP to the HTL enhanced the PCS's resistance to moisture while maintaining its high PCE. Taking advantage of the synergistic effects resulting from the combination of both fluoromethylated modifiers, we realize TFMBAI/TFP-based highly efficient PSCs with excellent operational stability and resistance to moisture, retaining over 96% of their initial efficiency after 500 h maximum power point tracking (MPPT) under simulated 1 sun irradiation and 97% of their initial efficiency after 1100 h of exposure under ambient conditions to a relative humidity of 60−70%.

Three hole-transporting materials (HTMs) based on the phenothiazine core containing 4,4-dimethyltriphenylamine (Z28), N-ethylcarbazole (Z29), and 4,4-dimethoxytriphenylamine (Z30) as the peripheral groups connected by double bonds were designed and synthesized. The HTMs were tested in mixed cation/anion perovskite solar cells (PSCs) of the composition [(FAPbI 3 ) 0.85 (MAPbBr 3 ) 0.15 ]. A power conversion efficiency (PCE) of 19.17% under 100 Mw cm −2 standard AM 1.5G solar illumination was obtained using Z30. Importantly, the devices based on Z30 show better stability compared to those using Z28 and Z29 when aged under ambient air of 40% relative humidity in the dark for 1008 h and under continuous sunlight soaking without encapsulation for 600 h. These results indicate that the 4,4-dimethoxytriphenylamine is a promising peripheral group in combination with the phenothiazine core, providing an alternative to develop small molecular HTMs for efficient and stable PSCs.

A rapid and simple process to prepare CH3NH3PbI3 perovskite solar cells in ambient air by adding 2-pyridylthiourea in the precursor solution was reported. The newly developed PSC exhibited an enhanced PCE of 18.2% along with enhanced stability under heat and humidity.

The toxicity of Pb and the instability of lead halide perovskites are the main obstacles to the practical application of lead-based nanocrystals (NCs). In this paper, all-inorganic Zn2+-doped lead-free perovskite (CsMn1–x Zn x Cl3) NCs were synthesized by a hot-injection method. Mn2+ ions were partially replaced by Zn2+ ions, and the energy transfer between Mn2+ was effectively suppressed. Because of this, excitons are more advantageously confined to the [MnCl6]4– octahedron. Target CsMn0.95Zn0.05Cl3 NCs were endowed with red emission at 654 nm with CIE coordinates of (0.70, 0.30) closing to the standard value of NTSC, and their photoluminescence quantum yield was increased to 77.1%, which is higher than those of Mn-based lead-free perovskites previously reported. Finally, a white light-emitting diode (LED) with adjustable emission from warm to cold white was realized by mixing Cs3MnBr5, CsMn0.95Zn0.05Cl3, and a blue phosphor on a 382 nm ultraviolet LED chip.

Developing hole-transporting materials (HTMs) with appropriate molecular configuration and charge mobility is important to improve perovskite solar cell (PSC) photovoltaic performance and their feasibility for commercialization. In this work, a novel pyramidal-shaped low-cost HTM coded MeOTTVT is prepared through extension of π-conjugation based on a triphenylamine core. Carbon–carbon double bonds are introduced between the core and p-methoxyl triphenylamine to improve the planarity of the HTM, favoring intermolecular stacking of MeOTTVT and thus improving the hole mobility of the corresponding hole-transporting layer (HTL). The p-methoxyl triphenylamine-endowed HTM benefits from a highest occupied molecular orbital level well-aligned with the perovskite active layer, facilitating effective hole extraction. The champion PSC using an MeOTTVT-based dopant additive-free HTL yielded a power conversion efficiency (PCE) up to 21.30%, which is considered one of the best-performing PSCs employing a dopant additive-free small molecule HTM. In addition, the MeOTTVT-based dopant additive-free HTL exhibits outstanding thermal stability and high glass-transition temperature (T g = 137.1 °C), combined with a more hydrophobic surface; PSCs based on an MeOTTVT dopant additive-free HTL exhibit outstanding stability against moisture, 1 sun illumination, and thermal stress.

Organic semiconducting single crystals are ideal building blocks for organic field-effect transistors (OFETs) and organic photodetectors (OPDs) because they can potentially exhibit the best charge transport and photoelectric properties in organic materials. Nevertheless, it is usual for single-crystal OFETs to be built from one kind of organic material in which the dominant transport is either electron or hole; such OFETs showing unipolar charge transport. Furthermore, single-crystal OPDs present high performance only in restricted regions because of the limited absorption of one-component single crystals. In an ideal situation, devices which comprise both electron and hole transporting single crystals with complementary absorptions, like single-crystalline p-n heterojunctions (SCHJs), can permit broadband photo-response and ambipolar charge transport. In this paper, a solution-processing crystallization strategy to prepare an SCHJ composed of C 60 and 6,13bis(triisopropylsilylethynyl)pentacene (TIPS-PEN) was shown. These SCHJs demonstrated ambipolar charge transport characteristics in OFETs with a balanced performance of 2.9 cm 2 V −1 s −1 for electron mobility and 2.7 cm 2 V −1 s −1 for hole mobility. This demonstration is the first of single-crystal OFETs in which both electron and hole mobilities were over 2.5 cm 2 V −1 s −1 . OPDs fabricated upon as-prepared SCHJs exhibited highly-sensitive photo-conductive properties ranging from ultraviolet to visible and further to near-infrared regions as a result of complementary absorption between C 60 and TIPS-PEN; thereby attaining the photo-responsivities amongst the highest-reported values within the organic photodetectors. This work would provide valuable references for developing novel SCHJ systems to achieve significant progress in high-performance ambipolar OFETs and broadband OPDs. IntroductionRecently, continuous research attention has been drawn to organic field-effect transistors (OFETs) for lightweight and deformable electronic applications like photodetectors, 1 sensors, 2 displays, 3 and circuits. 4 Included in these, organic photodetectors (OPDs), which translate optical signals into electrical signals, occupy an essential position in optical interconnection techniques, light-wave communications,

No abstract

Poor crystallinity of perovskite and extensive defects around grain boundaries are the acknowledged hindrances to obtaining high efficiency and long-term stability for organic metal halide perovskite solar cells (PSCs). Here, a 2D covalent organic framework (2D COF) nanosheets, [(TPA) 1 (TPhT) 1 ] CN , is first in situ synthesized in a PbI 2 layer with a highly crystalline structure to precisely regulate the crystallization process of perovskite in the sequential deposition method. The existence of 2D COF nanosheets can decelerate intermolecular interdiffusion and induce perovskite crystals to grow along (110) planes with enlarged grain size. Meanwhile, 2D COF nanosheets distributed around the grain boundaries reduce the defect density and promote carriers transporting in the perovskite film. The superior properties of the perovskite film afford the champion PSC device with a power conversion efficiency of 22.04%, which is over 10% higher than the control device. Moreover, the target PSC also demonstrates outstanding long-term stability. It can maintain over 90% of its initial value after 90 days storage in ambient conditions for unencapsulated devices. This work paves a new path for regulating the crystallization process of perovskites via 2D crystalline materials.