Conjugated Small Molecules: A Promising Hole Transport Materials in Perovskite Photovoltaics

There is a resurgence in the use of triphenylamine-based donor materials (TPA) in the field of perovskite photovoltaics. This work presents the synthesis of two novel conjugated small molecules (CSM's), TPA-t and TPA-t EH, which are functionalized with triisopropylsilyl groups and 2-ethylhexyl side chains. These molecules show promise as hole transport materials, which possess high hole mobilities of 1.5 × 10-4 and 2.9 × 10-3 cm2 V−1 s-1 due to self-organization. TPA-t and TPA-t EH possess HOMO energy levels at -5.38 and -5.31 eV, which is well-aligned with valence band of standard perovskite MAPbI3.This resulted in outstanding open-circuit voltages of 1100 and 1080 mV. TPA-based molecules were investigated as HTLs in n-i-p PSCs without additional doping and enabled high efficiency (17.4 %) same as for devices with state-of-the-art polytriarylamine (PTAA) HTL. The obtained results suggest that developed materials could potentially compete with PTAA when further material structure modification.