A “roller-wheel” Pt-containing small molecule that outperforms its polymer analogs in organic solar cells

Abstract

“Roller-wheel” shaped Pt-containing molecules display enhanced crystallinity and are better performing organic solar cell materials than conventional small molecules and polymers featuring “dumbbell” shaped structures.

“Roller-Wheel”-Type Pt-Containing Small Molecules and the Impact of “Rollers” on Material Crystallinity, Electronic Properties, and Solar Cell Performance

“…Devices were first constructed by using PC 61 BM as the electron acceptor and optimized by varying the fabrication conditions including spin-coating speed, weight ratios, concentrations and annealing conditions; then PC 71 BM was applied using the optimized condition for PC 61 BM. The optimization details for RWPt-1 are summarized in Table S1 and that for RWPt-2 is reported previously, 8 while optimized device parameters applying PC 71 BM are listed in Table 1. RWPt-1 and RWPt-2 gave OSC power conversion efficiencies (PCEs) up to 3.9% and 5.9%, respectively, and to the best of our knowledge, RWPt-2 has out-performed all existing Pt-containing polymers and SMs in OSC devices.…”

“…Accordingly, we have synthesized "roller-wheel" SMs RWPt-2 and RWPt-3, as shown in Scheme 1C. 8 Single crystals of RWPt-3 were obtained but showed no π-π interactions between organic chromophores, which resulted in poor OSC performance. On the other hand, RWPt-2 displayed much reduced bandgap and enhanced inter-molecular interactions when compared with RWPt-3, although no single crystals could be obtained to definitively prove the "slip-stack" geometry.…”

Red-shifted delayed fluorescence at the expense of photoluminescence quantum efficiency – an intramolecular charge-transfer molecule based on a benzodithiophene-4,8-dione acceptor

“…Benzo [1,2-b:4,5-b']dithiophene-4,8-dione is a heterocyclic homologue of anthraquinone, featuring two thiophene rings ortho-fused to an electron poor 1,4-benzoquinone core, this gives it moderately strong electron accepting properties. 1,2 It is most frequently encountered as an intermediate in the synthesis of ladder-type molecules [3][4][5][6][7][8][9][10][11] and high performance polymers [12][13][14][15][16][17][18][19][20] for organic solar cells (OSCs), while its electrochemical properties have been exploited in the development of organic batteries. [21][22][23][24] Efficient red thermally activated delayed fluorescence (TADF) is challenging due to the difficulty in simultaneously obtaining both a narrow singlet-triplet gap (E ST ) and a high fluorescence rate constant, and in overcoming the energy gap law which predicts that as the energy gap between the ground and excited states decreases, the rate of non-radiative decay (NRD) will increase.…”

A New Series of Conjugated Platinum‐co‐Poly(p‐phenylenebutadiynylene)s Polymers: Syntheses and Photophysical Properties

“…Designing ligand structures with donor–acceptor fragments as spacers reduces the bandgap of the polymers, thus increasing the efficiency of the solar cells . Alternatively, structural modifications of dimetallic platinum complexes from the “dumbbell” to the “roller‐wheel” can improve the crystallinity of the materials through intermolecular Π–Π interactions, consequently improving the efficiency of the solar cell . With respect to LEDs, introduction of N‐heterocyclic carbene in place of auxiliary phosphine in the platinum acetylide complexes can increase energy of the triplets states thus increasing the OLED performance …”