Unraveling Passivation Mechanism of Imidazolium-Based Ionic Liquids on Inorganic Perovskite to Achieve Near-Record-Efficiency CsPbI_(2)Br Solar Cells

The application of ionic liquids in perovskite has attracted wide-spread attention for its astounding performance improvement of perovskite solar cells(PSCs).However,the detailed mechanisms behind the improvement remain mysterious.Herein,a series of imidazolium-based ionic liquids(IILs)with different cations and anions is systematically investigated to elucidate the passivation mechanism of IILs on inorganic perovskites.It is found that IILs display the following advantages:(1)They form ionic bonds with Cs^(+)and Pb^(2+)cations on the surface and at the grain boundaries of perovskite films,which could effectively heal/reduce the Cs^(+)/I−vacancies and Pb-related defects;(2)They serve as a bridge between the perovskite and the hole-transport-layer for effective charge extraction and transfer;and(3)They increase the hydrophobicity of the perovskite surface to further improve the stability of the CsPbI_(2)Br PSCs.The combination of the above effects results in suppressed non-radiative recombination loss in CsPbI_(2)Br PSCs and an impressive power conversion efficiency of 17.02%.Additionally,the CsPbI_(2)Br PSCs with IILs surface modification exhibited improved ambient and light illumination stability.Our results provide guidance for an indepth understanding of the passivation mechanism of IILs in inorganic perovskites.

Decorating hole transport material with −CF_(3) groups for highly efficient and stable perovskite solar cells

The hole transport material (HTM) plays an extremely important role to determine the power conversion efficiency (PCE) and the stability of perovskite solar cells (PSCs). Herein, we report an effective strategy to improve the performance of HTMs by introducing −CF_(3) groups via the rational decorative mode. Upon direct attachment or nonconjugated alkoxyl bridging of −CF_(3) groups on the terminal diphenylamines, the resulting molecular HTMs, i.e., 2,7-BCzA4CF_(3) and 2,7-BCzA4OCCF_(3), show distinct properties. Compared with 2,7-BCzA4CF_(3), the nonconjugated alkoxyl bridging −CF_(3) group-based 2,7-BCzA4OCCF_(3) exhibits better thermal stability, hydrophobicity, and a dramatically upgraded hole mobility by 135.7-fold of magnitude to 1.71 × 10^(−4) cm^(2) V^(−1) S^(−1). The PSCs with 2,7-BCzA4OCCF_(3) as HTM exhibit an PCE of up to 20.53% and excellent long-term stability, maintaining 92.57% of their performance for 30 days in air with humidity of 30% without encapsulation. This work provides beneficial guidelines for the design of new HTMs for efficient and stable PSCs.

High detectivity photodetectors based on perovskite nanowires with suppressed surface defects

Solution-processable,single-crystalline perovskite nanowires are ideal candidates for developing low-cost photodetectors,but their detectivities are limited due to a high level of unintentional defects.Through the surfaceinitiated solution-growth method,we fabricated high-quality,single-crystalline,defects-suppressed MAPbI_(3) nanowires,which possess atomically smooth side surfaces with a surface roughness of 0.27 nm,corresponding to a carrier lifetime of 112.9 ns.By forming ohmic MAPbI_(3)∕Au contacts through the dry contact method,highperformance metal–semiconductor–metal photodetectors have been demonstrated with a record large linear dynamic range of 157 dB along with a record high detectivity of 1.2×10^(14) Jones at an illumination power density of 5.5 nW∕cm^(2).Such superior photodetector performance metrics are attributed to,first,the defects-suppressed property of the as-grown MAPbI_(3) nanowires,which leads to a quite low noise current in the dark,and second,the ohmic contact between MAPbI_(3) and Au interfaces,which gives rise to an improved responsivity compared with the Schottky contact counterpart.The realized high-performance MAPbI_(3) nanowire photodetector advances the development of low-cost photodetectors and has potential applications in weak-signal photodetection.

分子工程优化含吡啶受体的二硫富瓦烯敏化剂用于高效染料敏化太阳电池（英文）

近年来,具有给体-π桥-受体结构的有机化合物作为光敏剂用于染料敏化太阳电池的研究引起广泛关注.研究发现吡啶作为电子受体和吸附基团时可实现有效的电子注入.为了提高含吡啶受体有机敏化剂的性能,需要通过分子工程对电子给体,π桥和分子结构在分子层面上进行优化.本研究以二硫富瓦烯为电子给体,吡啶为电子受体,合成了两个π桥结构分别为噻吩-苯和苯-噻吩的单体型敏化剂DTFPy3和DTFPy4,对二者及其对应的二聚体型敏化剂D-DTFPy3和D-DTFPy4的研究发现,调整π桥上富电子噻吩靠近给体一端时可使敏化剂的吸收波长红移.另外,二聚体型敏化剂可有效提高敏化剂的吸光强度.在这四个敏化剂中,D-DTFPy4表现出最佳的光捕获效率,以其制备的染料敏化太阳电池,光电转换效率可达5.26%.