A Trifluoroethoxyl Functionalized Spiro‐Based Hole‐Transporting Material for Highly Efficient and Stable Perovskite Solar Cells

Abstract

It is crucial to finely optimize the properties of hole transport materials (HTMs) to improve the performance and stability of perovskite solar cells (PSCs). Herein, a new spiro‐based HTM (Spiro‐4TFETAD) is developed by replacement of partial methoxy groups in Spiro‐OMeTAD with trifluoroethoxy substituents. Spiro‐4TFETAD has lower highest occupied molecular orbital level, higher thermal stability (Tg = 140 °C), hole mobility (2.04 × 10−4 cm2 V−1 s−1), and better hydrophobicity with respect to Spiro‐OMeTAD. The PSCs using Spiro‐4TFETAD achieve a power conversion efficiency of 21.11% and excellent humidity resistance. It maintains an average 83% of their initial power conversion efficiency values even in high relative humidity of 60% without encapsulation and 82% of its initial performance after 100 h continuous illumination at the maximum power point. The superior performance underscores the promising potential of the trifluoroethoxyl molecular design in preparing new HTMs toward highly efficient and stable PSCs.

Dibenzo heterocyclic-terminated spiro-type hole transporting materials for perovskite solar cells

“…The above similar results have been observed in many reports. 22,23,25 It can also be believed that the devices with higher V oc may be obtained after carefully optimizing the amount of additives. 22,23 And it is worth noting that the performance of the developed HTMs with or without additives is opposite.…”

“…[17][18][19][20] To date, 2,2 0 ,7,7 0 -tetrakis(N,N-di-p-methoxyphenyl-amine)-9,9 0 -spirobifluorene (spiro-OMeTAD) has been the mostly used spiro-type HTM for efficient PSCs. Recently, the replacement of partial anisole on spiro-OMeTAD by other functional groups has been proved as an efficient way to improve the photoelectric performance of PSCs, such as para-and meta-anisole, 21 fluorene, 22 N-ethylcarbazole, 23,24 trifluoroethoxyl functionalized anisole, 25 thioanisole, 26 methoxynaphthalene, 27 fluorine functionalized anisole, 28 etc. Though the above reported new HTMs exhibit a higher PCE than spiro-OMeTAD in their work, it is noteworthy that spiro-OMeTAD still retains the highest reported PCE (25.8%) in PSCs.…”

Catalytic Stereoselective Multicomponent Reactions for the Synthesis of Spiro Derivatives: Recent Progress

“…Enantioenriched spiro derivatives [12] are characterized by the interesting fusion of two molecular rings linked by a common tetrasubstituted stereogenic center. They are an important component of several natural products, [13–15] bioactive compounds, [16–20] and find applications in asymmetric catalysis, [21–24] thermally stable OLED, [25–31] sensing, [32–36] and HMT (hole‐transporting material) [37–46] . Compared with singly condensed heterocycles spiro‐hetero/carbocycles have the obvious advantage of structural compactness, which reduces lipophilicity [47] .…”

“…They are an important component of several natural products, [13][14][15] bioactive compounds, [16][17][18][19][20] and find applications in asymmetric catalysis, [21][22][23][24] thermally stable OLED, [25][26][27][28][29][30][31] sensing, [32][33][34][35][36] and HMT (hole-transporting material). [37][38][39][40][41][42][43][44][45][46] Compared with singly condensed heterocycles spiro-hetero/carbocycles have the obvious advantage of structural compactness, which reduces lipophilicity. [47] Moreover, the 3D modification in such molecules is promoted by the isomerization process, [48] and the excellent sp 3 : sp 2 ratio enables the development of completely new organic molecules with improved biological properties.…”

A N‐Ethylcarbazole‐Terminated Spiro‐Type Hole‐Transporting Material for Efficient and Stable Perovskite Solar Cells

“…[17][18][19][20][21] Among them, spiro-centered molecules, especially 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-OMeTAD), are still recognized as the most efficient HTM in PSCs [22] because of the superiority from their twisted structures granting suitable energy levels for transporting holes and blocking electrons. [18] To achieve efficient PSCs, many works have been devoted to further engineering the spiro-typed HTMs by partial altering the terminal anisole by other functional groups, such as para-and meta-anisole, [23] fluorene, [24] carbazole, [25,6] thioanisole, [27] fluorine functionalized anisole, [28] trifluoroethoxyl functionalized anisole, [29] and methoxynaphthalene, [30] and so on. Above reported new spiro-centered HTMs display higher PCE than spiro-OMeTAD; however, it should be noted that the spiro-OMeTAD still retains the maximum reported PCE (25.8 %) in PSCs.…”