Research Article: Self‐Organized Fullerene Interfacial Layer for Efficient and Low‐Temperature Processed Planar Perovskite Solar Cells with High UV‐Light Stability

Date Published: April 19, 2017

Publisher: John Wiley and Sons Inc.

Author(s): Jiangsheng Xie, Xuegong Yu, Jiabin Huang, Xuan Sun, Yunhai Zhang, Zhengrui Yang, Ming Lei, Lingbo Xu, Zeguo Tang, Can Cui, Peng Wang, Deren Yang.

http://doi.org/10.1002/advs.201700018

Abstract

In this Communication, a self‐organization method of [6,6]‐phenyl‐C61‐butyric acid 2‐((2‐(dimethylamino)‐ethyl) (methyl)amino)ethyl ester (PCBDAN) interlayer in between 6,6‐phenyl C61‐butyric acid methyl ester (PCBM) and indium tin oxide (ITO) has been proposed to improve the performance of N–I–P perovskite solar cells (PSCs). The introduction of self‐organized PCBDAN interlayer can effectively reduce the work function of ITO and therefore eliminate the interface barrier between electron transport layer and electrode. It is beneficial for enhancing the charge extraction and decreasing the recombination loss at the interface. By employing this strategy, a highest power conversion efficiency of 18.1% has been obtained with almost free hysteresis. Furthermore, the N–I–P PSCs have excellent stability under UV‐light soaking, which can maintain 85% of its original highest value after 240 h accelerated UV aging. This self‐organization method for the formation of interlayer can not only simplify the fabrication process of low‐cost PSCs, but also be compatible with the roll‐to‐roll device processing on flexible substrates.

Partial Text

Perovskite Solar Cell Fabrication: The ITO was cleaned sequentially in deionized water, cleaning fluid, acetone, and ethanol under sonication for 5 min, respectively. Then the ITO was dried by nitrogen gas and treated with UV‐Ozone machine for 20 min. PCBDAN was synthesized with literature method.49 PCBM, PCBM:PCBDAN (χ:1, χ = 19, 9, 4, 1 by weight) blend, and PCBDAN materials were dissolved in chlorobenzol solution, respectively. The ETL layer on ITO with thicknesses of ≈25, 40, 60, 80 nm was attained by spin‐coating the chlorobenzol solution with concentrations of 10, 12.5, 15, and 17.5 mg mL−1 at a rate of 2000 rpm for 60s, respectively. The 120 nm ITO/PCBM:PCBDAN sample for EDS measurements was attained by spin‐coating the chlorobenzol solution of PCBM:PCBDAN (9:1 by weight) with 25 mg mL−1. For the PCBDAN/PCBM bilayer, 2 mg mL−1 PCBDAN and 12.5 mg mL−1 PCBM chlorobenzol solution were spin‐coated on ITO substrates at 2000 rpm successively. The ITO/ETL layer was then followed by thermal annealing at 100 °C for 10 min. For planar TiO2 ETL, an acidic solution of titanium isopropoxide in ethanol (the concentrations of titanium isopropoxide/2 m HCl/ethanol = 254 µL/34 µL/2 mL) was spin‐coated on the FTO at 2000 rpm for 40 s, and then annealed in air at 500 °C for 30 min. The 461 mg of PbI2, 159 mg of CH3NH3I, and 78 mg of DMSO (molar ratio 1:1:1) were mixed in 600 mg of dimethyl formamide (DMF) solution. The prepared solution was dropped on different substrates and then rapidly spin‐coated at 1000 rpm for 10 s and 5000 rpm for another 20 s. 0.6 mL of diethyl ether was drop‐casted quickly 15 s before the 5000 rpm spin‐coating ended. The perovskite films were heated at 70 °C for 1 min and 100 °C for 10 min on a hotplate, respectively. After several minutes, a hole‐transport material was spin‐coated on the top of perovskite film at the rotation speed of 3000 rpm for 30 s in glovebox. The hole‐transport solution was prepared by dissolving 72.3 mg spiro‐MeOTAD, 17.5 mL of a stock solution of 520 mg mL−1 lithium bis(trifluoromethylsulphonyl)imide in acetonitrile and 28.8 mL 4‐tert‐butylpyridine in 1 mL chlorobenzene. At last, 100 nm thick Au electrode were deposited under high vacuum (<1.0 × 10–3 Pa). For all devices, the active area is 10 mm2. For UV‐stability measurement, the perovskite solar cells with PCBM:PCBDAN and TiO2 ETLs were aged under 365 nm 190 mW cm−2 UV illuminations in N2 atmosphere. All the devices were unpaged and measured in air with ≈45% humidity.   Source: http://doi.org/10.1002/advs.201700018

 

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