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A star-shaped hole-transporting material (HTM) using the triphenylamine (TPA) as the core named TP1 is designed and synthesized. The implementation of the new HTM in CH3NH3PbI3-based perovskite solar cells exhibits an excellent overall power conversion efficiency (PCE) of 12.63 % without the use of any dopants and additives, which is comparable to the 14.93 % obtained using p-doped spiro-OMeTAD. Importantly, the devices based on TP1 show relatively stable device performance compared to spiro-OMeTAD after aging in ambient air with 30 % relative humidity without encapsulation in the dark. The present results demonstrate that TPA could be an excellent building block to design dopant-free HTMs for perovskite solar cells and holds promise to replace p-doped spiro-OMeTAD, which is important for the fabrication of cost-effective and stable devices. [ABSTRACT FROM AUTHOR]

Two hole-transporting materials (HTMs) based on N, N, N′,N′- tetraphenylbenzidine (TPB) and MeO-triphenylamine (MOTPA) are synthesized. The HTMs offer outstanding thermal stability, film-forming properties, and hole mobilities. Perovskite solar cells (PSCs) are prepared using either pristine HTM layers or layers doped with cobalt salts. The nondoped PSCs with as-synthesized HTMs show better performance compared to spiro-OMeTAD, especially for long-time stability in ambient air. The power conversion efficiency (PCE) of the cells decreases by only 3 % after 600 h of storage. The nondoped hole-transport layer (HTL) are hydrophobic, with a contact angle of 94.3° to water. The moisture-repelling ability of these HTMs are demonstrated by exposing the nondoped PSCs to an atmosphere saturated with water vapor. The PCE of doped PSCs with spiro-OMeTAD as HTL decreased 53 %, while that of nondoped PSCs with the as-synthesized HTMs as HTL only decreased 27 % after 15 min. These result thus show a new method to improve the operational stability of PSCs, especially at high humidity levels. [ABSTRACT FROM AUTHOR]

A triphENylamine based molecular “butterfly” is developed as dopant ‐ free hole ‐ transport material for perovskite solar cells exhibiting excellENt power conversion efficiENcy of 16.3% which is comparable to the state ‐ of ‐ the ‐ art doped 2,2′,7,7′ ‐ tetrakis(N,N′ ‐ di ‐ p ‐ methoxy ‐ phENylamine) ‐ 9,9′ ‐ spirobifluorENe (spiro ‐ OMeTAD). Moreover, the device is much more stable than that of spiro ‐ OMeTAD based device under light irradiation. [ABSTRACT FROM AUTHOR]

Two star-shaped TPA-based small-molecule materials (Z1012 and Z1013) were designed and synthesized in this paper. These molecules show high hole mobility and suitable energy levels for CH 3 NH 3 PbI 3 -based perovskite solar cells. Photovoltaic cells based on the Z1013 without any dopants or additives achieve an excellent power conversion efficiency (PCE) of 15.4%, which is comparable to devices based on state-of-art p-doped spiro -OMeTAD. Moreover, the devices based on these two HTMs show much better stability than that of devices based on spiro -OMeTAD when aging in ambient air both at room temperature and 80 °C. These results demonstrate that star-shape TPAs could be excellent dopant-free HTMs for perovskite solar cells and hold promise to replace the p-doped spiro -OMeTAD, which is important for the fabrication of cost-effective and stable devices. [ABSTRACT FROM AUTHOR]

We report two simple triphenylamine-based hole-transporting materials (HTMs) containing vinyl derivatives, 3,6-di(2-(4-(N,N-di(p-tolyl)amino)phenyl)vinyl)-2-thiophene (apv-T) and 3,6-di(2-(4-(N,N-di(p-tolyl)amino)phenyl)vinyl)-9-ethyl-carbazole (apv-EC) for the perovskite solar cells. According to theoretical calculation and experimental results, their HOMO energy levels are similar to that of conventional spiro -OMeTAD, which is supposed to be favorable for the hole transportation in the device. Up to 12% of light-to-electricity conversion efficiency has been achieved for the mesoporous TiO 2 /CH 3 NH 3 PbI 3 /apv-EC/Au solar cell without using p -type dopants. Time-resolved photoluminescence (PL) measurement and Electrochemical Impedance Spectra (EIS) further reveal that relatively high hole mobility of the apv-EC and weak recombination occurred at TiO 2 /CH 3 NH 3 PbI 3 /apv-EC interfaces of the device are crucial to the good performance in comparison with the apv-T. Advantages such as easy synthesis, low cost and relatively good cell performance provide a potential application as the replacement of the expensive spiro -OMeTAD. [ABSTRACT FROM AUTHOR]