We prepared the novel fullerene derivative (a-bis-PCBM) by separating it from the as-produced bis-phenyl-C 61 -butyric acid methyl (bis-[60] PCBM) ester isomer mixture using preparative peak-recycling high performance liquid chromatography (HPLC). We employed the compound as a templating agent for the solution processing of metal halide perovskite films by the antisolvent method. Perovskite solar cells (PSCs) containing a-bis-PCBM perovskite achieve better stability, efficiency, and reproducibility compared with those employing traditional PCBM. The a-bis-PCBM can fill the vacancies and grain boundaries of the perovskite film, enhancing the crystallization of perovskites and addressing the issue of 2 slow electron extraction. In addition, it can also resist the ingression of moisture, protect the interfaces from chemical erosion, and passivate the voids or pinholes generated in the holetransporting layer. As a result, we obtain an outstanding power conversion efficiency (PCE) of 20.8 % compared with 19.9 % by PCBM, accompanied by excellent stability under heat and simulated sunlight,. The PCE of unsealed devcies dropped by less than 10% in ambient air (40% RH) after 44 days at 65 ℃ and by 4% after 600 h under continuous full sun illumination and maximum power point tracking respectively.Hybrid organic-inorganic lead halide perovskite solar cells (PSCs) have emerged as a promising candidate for the next generation photovoltaic technology due to their low manufacturing cost and high performance. 1−6 Through judicious manipulation of perovskite morphology and improvement of interfacial properties, 2−6 PSCs have reached a certified power conversion efficiency (PCE) up to 22.1%. 7 Generally, the PSCs with the best performance employ a sandwich configuration, composed of a layer of TiO 2 electron selective contact, which is infiltrated by the intrinsic perovskite light harvester, followed by a layer of hole transport material (HTM) as p-type contact and a metal back contact. 8 Despite of these stunning advances, several challenges still remain before PSCs become a competitive commercial technology, one crucial issue being the device stability. 9−11 Uncontrolled film morphology associated with poor crystallity of the perovskites results in low efficiency and poor reproducibility of the device performance. 12 Previous studies have indicated that the degradation of PSCs is primarily governed by the ingress of atmospheric oxygen and water vapor into the film upon exposure to air, which in turn causes undesired reactions with the active materials. 13,14 Various methods have been tried to modify the morphology of perovskite films aiming to improve the stability, for example, poly(methyl methacrylate) (PMMA) was used as a template to control nucleation and crystal growth, resulting in considerable increase in both the device efficiency and stability when kept under 3 dry condition in the dark. 15 Other studies use additives like 1-methyl-3-(1H,1H,2H,2H-nonafluorohexyl)-imidazolium iodide, 16 or phenyl-C 61 -b...

The exploration of alternative low-cost molecular hole-transporting materials (HTMs) specifically for both high efficient and stable perovskite solar cells (PSCs) is a relatively new research area. Two novel HTMs using the thiophene core were designed and synthesized (Z25 and Z26). The Z26-based perovskite solar cells exhibited a remarkable overall power conversion efficiency (PCE) of 20.1 %, which is comparable to 20.6% obtained by spiro-OMeTAD-based device. Importantly, the devices based-on Z26 show better stability 2 compared to devices based on Z25 and spiro-OMeTAD when aged under ambient air of 30% or 85% relative humidity in the dark and under continuous full sun illumination at maximum power point tracking respectively. The presented results clearly qualify a simple strategy by introduction of double bonds to design hole transporting materials for highly efficient and

Two TPB-based HTMs were synthesized and their energy levels were tuned to match with perovskite by introducing electron-donating groups asymmetrically. The TPBC based doping-free perovskite solar cell afforded an impressive PCE of 13.10% under AM 1.5G illumination, which is the first case of an effective device with TPB-based doping-free HTMs.

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Novel small-molecule hole transporting materials (HTMs) with a linear π-conjugated structure have been synthesized. The perovskite solar cell based on as the HTM exhibits an encouraging power conversion efficiency of 9.1% under AM 1.5 G (100 mW cm(-2)) illumination, which is the first demonstration of an effective perovskite solar cell using a linear structured HTM.