Search

Dye‐sensitized solar cells (DSCs) based on copper(II/I) redox mediators have recently achieved notable performance progress through tailoring the ligand structure of the copper complexes, exploiting cosensitization, and introducing an advanced device structure. In order to further improve the power conversion efficiency (PCE), it is imperative to develop wide spectral‐response photosensitizers compatible with the copper(II/I) redox mediators while attaining a high Voc. Herein, a blue photosensitizer coded R7 is reported, which is purposely designed for highly efficient DSCs with copper‐based electrolytes. R7 features a strong electron‐donating segment of 9,19‐dihydrobenzo[1′,10′ ]phenanthro[3′,4′:4,5]thieno[3,2‐b]benzo[1,10]phenanthro[3,4‐d]thiophene conjugated with 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 and the electron acceptor 4‐(7‐ethynylbenzo[c][1,2,5]thiadiazol‐4‐yl)benzoic acid. The blue dye R7 with bulkier auxiliary donor moiety in the DSC largely outperforms the reference dye R6, which has a smaller bis(4‐(hexyloxy)phenyl)amine donor unit. Transient absorption spectroscopy and electrochemical impedance spectroscopy measurements show that the R7 based DSC has a higher charge separation yield, a higher charge collection efficiency, and lower charge recombination with the copper electrolyte than the R6 based counterpart. A cosensitized system of R7 and Y123 for the DSC presents an outstanding PCE of 12.7% and retains 90% of its initial value after 1000 h of light soaking under 1 sun at 45 °C. [ABSTRACT FROM AUTHOR]

Four ZnPc‐dimers with 2,5‐thienyl (ZnPc−th−ZnPc 1), 2,7‐fluorenyl (ZnPc−flu−ZnPc 2), 3,6‐bisthienylldiketopyrrolopyrrole (ZnPc−DPP−ZnPc 3) and 1,4‐phenyl (ZnPc−p−ZnPc 4) bridges have been studied as dopant‐free hole transporting materials (HTMs) in perovskite solar cells (PSCs). The synthesis and characterization of ZnPc−th−ZnPc 1 and ZnPc−flu−ZnPc 2 dimers are reported for the first time. Steady state and time resolved photoluminescence demonstrate the good hole‐extraction capability of these materials. The best efficiencies obtained for dimers 1, 2, 3 and 4 are 15.5 %, 15.6 %, 16.8 % and 15.7 %, respectively, without the addition of dopants. Besides, these derivatives demonstrated better stability both in dark storage conditions with a relative humidity <20 % for 500 h and at 50 °C with a relative humidity >60 % for 160 h when compared to doped spiro−OMeTAD. The push‐pull nature of dimer ZnPc−DPP−ZnPc 3 has led to the highest efficiency among the ZnPc derivatives under study demonstrating that donor‐acceptor‐donor systems can be good alternatives to commonly used materials due their energy levels, low cost and the final morphology of the hole transporting layer. [ABSTRACT FROM AUTHOR]

A new tandem electrolyte composed of two redox pairs, the organic radical 2-azaadamantane-N-oxyl (AZ) and the well-known redox pair [Co(bpy)3]3+/2+ was investigated in dye sensitized solar cells. Importantly, an increase in VOC was achieved using the new tandem redox system with values up to 1007 mV, compared to only 896 mV for the reference [Co(bpy)3]3+/2+ couple. Consequently, the tandem electrolytes presented higher device performance in conjunction with the organic dye XY1. It was determined that the VOC improvement is mainly attributed to the combined effect of two factors: the more positive redox potential of the small donor AZ (0.81 V vs. SHE) and improved recombination resistance in the tandem electrolytes. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells (DSSCs) have attracted a substantial interest in the last 30 years for the conversion of solar power to electricity. An important component is the redox mediator effecting the transport of charge between the photoelectrode and the dark counter electrode (CE). Among the possible mediators, metal coordination complexes play a prominent role and at present are incorporated in several types of devices with a power conversion efficiency exceeding 10%. The present review, after a brief introduction to the operation of DSSCs, discusses at first the requirements for a successful mediator. Subsequently, the properties of various classes of inorganic coordination complexes functioning as mediators relevant to DSSC operation are presented and the operational characteristics of DSSC devices analyzed. Particular emphasis is paid to the two main classes of efficient redox mediators, the coordination complexes of cobalt and copper; however other less efficient but promising classes of mediators, notably complexes of iron, nickel, manganese and vanadium, are also presented. [ABSTRACT FROM AUTHOR]