Mahmud Md Arafat, Elumalai Naveen Kumar, Upama Mushfika Baishakhi, Wang Dian, Gonçales Vinicius R, Wright Matthew, Xu Cheng, Haque Faiazul, Uddin Ashraf
School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, NSW 2052, Australia.
Phys Chem Chem Phys. 2017 Aug 9;19(31):21033-21045. doi: 10.1039/c7cp03551a.
Here we report a small molecule oxidant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4TCNQ) doped, low cost 2',7'-bis(bis(4-methoxyphenyl)amino)spiro[cyclopenta[2,1-b:3,4-b']dithiophene-4,9'-fluorene] (FDT) hole transporting layer (HTL) for efficient mixed organic cation based MAFAPbI (MA = methyl ammonium, FA = formamidinium) perovskite solar cells (PSCs), fabricated via a highly reproducible controlled nucleation assisted restricted volume solvent annealing method, having full temperature compatibility with flexible substrates. The optimized (1 wt%) F4TCNQ doped FDT HTL based devices (F-FDT devices) demonstrate simultaneous enhancement of photovoltaic performance and device stability as well as significant reduction in photo-current hysteresis, as compared to conventional bis(trifluoromethylsulfonyl)amine lithium (Li-TFSI) additive based FDT HTL devices (L-FDT devices). Adding to the merits, F-FDT PSCs exhibit about 75% higher device stability compared to conventional L-FDT devices during the course of three weeks. Mott-Schottky analysis and in-depth charge transport characterization were carried out using electrochemical impedance spectroscopy (EIS) of the fabricated devices to understand the superior performance of the F-FDT devices. In addition, detailed polaronic intensity characterization of the doped HTL films was performed via ultraviolet-visible near-infrared (UV-vis-NIR) spectroscopy to investigate the underlying mechanism. Mitigated photocurrent hysteresis in the F-FDT devices has also been examined in terms of the inherent electrode polarization phenomenon. Furthermore, the superior device stability of the F-FDT PSCs has been probed in terms of variation in electronic properties, surface wettability, crystallinity, and microstrain dislocation density, and a detailed picture of the underlying mechanism behind stability enhancement is presented.
在此，我们报道了一种小分子氧化剂2,3,5,6-四氟-7,7,8,8-四氰基对苯二醌二甲烷（F4TCNQ）掺杂的低成本2',7'-双（双（4-甲氧基苯基）氨基）螺[环戊[2,1-b:3,4-b']二噻吩-4,9'-芴]（FDT）空穴传输层（HTL），用于高效的基于混合有机阳离子的MAFAPbI（MA = 甲基铵，FA = 甲脒）钙钛矿太阳能电池（PSC），该电池通过高度可重现的受控成核辅助受限体积溶剂退火方法制备，与柔性基板具有完全的温度兼容性。与传统的基于双（三氟甲基磺酰）胺锂（Li-TFSI）添加剂的FDT HTL器件（L-FDT器件）相比，优化的（1 wt%）F4TCNQ掺杂FDT HTL基器件（F-FDT器件）表现出光伏性能和器件稳定性的同时增强，以及光电流滞后的显著降低。此外，与传统的L-FDT器件相比，F-FDT PSCs在三周的过程中表现出约75%更高的器件稳定性。使用所制备器件的电化学阻抗谱（EIS）进行了莫特-肖特基分析和深入的电荷传输表征，以了解F-FDT器件的优异性能。此外，通过紫外-可见近红外（UV-vis-NIR）光谱对掺杂HTL薄膜进行了详细的极化子强度表征，以研究其潜在机制。还从固有电极极化现象的角度研究了F-FDT器件中减轻的光电流滞后。此外，从电子性质、表面润湿性、结晶度和微应变位错密度的变化方面探讨了F-FDT PSCs优异的器件稳定性，并给出了稳定性增强背后潜在机制的详细情况。
