| 초록 |
One of the most prominent hole-transporting material (HTM) for hybrid perovskite solar cells (PSCs) has been 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-OMeTAD), which is commonly doped with metal bis(trifluoromethylsulfonyl)imide (M(TFSI)n) salts that contribute to generating the active radical cation HTM species. The underlying role of the metal cation, however, remains elusive. Here, we analyze the effect of metal cations on doping spiro-OMeTAD by a combination of techniques, including electron paramagnetic resonance (EPR) and UV-vis absorption spectroscopy, which is complemented by photovoltaic device and hole mobility analysis. As a result, we reveal the superiority of Zn-based TFSI salts in device performance as compared to the others, including redox-active Cu(TFSI)2. This analysis thereby unravels some of the design principles for dopant engineering in HTMs for hybrid perovskite photovoltaics. |
