Indacenodithiophene\nBridged Dimeric Porphyrin Donor\nand Absorption Complementary Indacenodithiophene Acceptor for Nonfullerene\nOrganic Photovoltaics

Abstract

Porphyrins are one\nof the most promising materials for organic\nphotovoltaics (OPVs) because of their easily tunable functional groups.\nHerein, we present the design and synthesis of two porphyrin-based\nsmall molecule donors, IDT-2TPE and TPE, in which two porphyrin units\nare bridged by an indacenodithiophene (IDT) diethynylene unit for\nthe former and a single porphyrin monomer for the latter, and 3-ethylrhodanine\nunits are then end-capped symmetrically by phenylenethynylene π-linkers.\nThe porphyrin dimer IDT-2TPE exhibits outstanding red-shifted absorptions\nwith a valley in both solution (400–800 nm) and film (400–900\nnm), low-lying energy levels, and excellent thermal stability compared\nto the porphyrin monomer TPE due to the extended π-conjugation\nand increased rigidity with the IDT unit. Impressively, the device\nbased on the IDT-2TPE donor and IDTCR nonfullerene acceptor shows\na broad photoelectron response up to 1000 nm and a power conversion\nefficiency (PCE) of 10.41% at AM 1.5G. For comparison, the device\nbased on the TPE donor and IDTCR acceptor has a much lower PCE of\n4.22%. The much better performance of the device IDT-2TPE/IDTCR is\nattributed to its higher photocurrent generation and more favorable\nsurface morphology with elevated charge carrier mobilities.