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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]