Charge-Transfer State Dissociation Efficiency Can Limit Free Charge Generation in Low-Offset Organic Solar Cells.

We investigate the charge-generation processes limiting the performance of low-offset organic bulk-heterojunction solar cells by studying a series of newly synthesized PBDB-T-derivative donor polymers whose ionisation energy (IE) is tuned via functional group (difluorination or cyanation) and backbone (thiophene or selenophene bridge) modifications. When blended with the acceptor Y6, the series present heterojunction donor-acceptor IE offsets () ranging from 0.22 to 0.

Insight into the Properties of Heteroleptic Metal Dithiolenes: Multistimuli Responsive Luminescence, Chromism, and Nonlinear Optics.

A comprehensive investigation of the functional properties of heteroleptic donor-M-acceptor dithiolene complexes BuN[M(L1)(L2)] is presented (M = Pd, Pt). The acceptor L1 consists of the chiral ()-(+)α-methylbenzyldithiooxamidate (()-α-MBAdto), the donor L2 is 2-thioxo-1,3-dithiole-4,5-dithiolato (dmit) in (Pd) and (Pt), 1,2-dicarbomethoxyethylenedithiolate (ddmet) in (Pd) and (Pt), or [4',5':5,6][1,4]dithiino[2,3-]quinoxaline-1',3'-dithiolato (quinoxdt) in (Pd) and (Pt). L1 is capable of undergoing proton exchange and promoting crystal formation in noncentrosymmetric space groups.

Anti-Kasha Conformational Photoisomerization of a Heteroleptic Dithiolene Metal Complex Revealed by Ultrafast Spectroscopy.

We investigated the anti-Kasha photochemistry and anti-Kasha emission of d-metal donor-acceptor dithiolene with femtosecond UV-vis transient absorption spectroscopy and molecular modeling. Experimentally, we found a lifetime of 1.4 ps for higher excited states, which is exceptionally long when compared to typical values for internal conversion (IC) (10 s of fs or less).

Uncommon Optical Properties and Silver-Responsive Turn-Off/On Luminescence in a Pt Heteroleptic Dithiolene Complex.

Complex [Pt(iPr pipdt)(Quinoxdt)] (iPr pipdt=1,4-diisopropyl-piperazine-2,3-dithione; Quinoxdt=[1,4]dithiino[2,3-b]quinoxaline-2,3-dithiolate) exhibits a remarkable green emission at 570 nm (room temperature), which is above the lowest excited state. The complex is characterized by negative solvatochromism as well as a high second-order polarizability. Addition of Ag ions induces 1) hypsochromic shift of the lowest frequencies and 2) reversible quenching of luminescence.