Bulky 3D Structures of Dithienopyrrol Dye with Copper(II/I) Redox Mediator Enabling Efficient Solar Cells with an Open-Circuit Voltage of 1.13 V

Efficiently suppressing on interface recombination of dye-sensitized solar cells (DSCs) enables high open-circuit photovoltage (Voc) through exploiting photosensitizers. Herein, a dithienopyrrol derivative photosensitizer C260A featuring a bulky auxiliary donor N-(2',4'-bis(hexyloxy)-[1,1'-biphenyl]-4-yl)-2',4'-bis(hexyloxy)-N- methyl-[1,1'-biphenyl]-4-amine (BP-DPA) and a traditional electron-acceptor cyanoacrylic acid (CA) was reported. Dye C260A with a bulky auxiliary donor moiety in the DSC outperforms the reference dye C260 with the state-of-the-art donor bis(4(hexyloxy)phenyl)amine (DPA). Although the substitution of bulky auxiliary donor hardly alters the optical energy gap, C260A possesses prolonged equilibrium excited-state lifetimes in both dye-diluted solution and dye-grafted alumina film than the C260-based counterpart. These two photosensitizers are used to make coadsorbate-free, highphotovoltage-output DSCs in combination with a Cu(II/I) redox mediator. Electric and photophysical measurements show that the C260A-based DSC endows a higher charge collection efficiency and a lower charge recombination rate with the copper electrolyte than the C260-based counterpart. DSC with the bulky auxiliary donor-based photosensitizer C260A achieves a high open-circuit photovoltage of 1.13 V, yielding a good power conversion efficiency (PCE) of 10.3% at 100 mW cm(-2), simulated AM1.5G conditions. The cosensitization of C260A with the perylene dye C272 obtains an efficient DSC with an impressive PCE of 11.0%.

Automated summary

Efficient suppression of interface recombination in dye-sensitized solar cells (DSCs) is achieved by utilizing a novel photosensitizer C260A. The bulky auxiliary donor moiety in C260A leads to improved charge collection efficiency and reduced charge recombination rate. Furthermore, coadsorption of C260A and perylene dye C272 results in a highly efficient DSC.