Chlorophyll-based organic solar cells with improved power conversion efficiency

Chlorophylls(Chls), and associated chlorophyll derivatives, are one of the oldest, most versatile organic semiconductors found in nature. Herein, we present two easily semi-synthesized chlorophyll derivatives, namely, chlorin e6 trimethyl ester(Ce6Me3) and its copper complex(Cu–Ce6 Me3), as the p-type dopants for organic semiconductors and their impact in organic solar cells(OSCs). In our study, both Chls showed intense Soret and Q y bands in the UV-visible spectra, leading to an effect means for capturing solar light and energy. Chls also exhibited high carrier mobility owing to the partial formation of aggregates through the spin-coating process. Using Chls, we fabricated OSCs in both planar-heterojunction(PHJ) and bulkheterojunction(BHJ) solar cell configurations, together with C70/PC70 BM as electron acceptors. In PHJ solar cells, we received solar power conversion efficiencies(PCEs) of only 0.85% and 0.93% for Cu–Ce6 Me 3-and Ce6Me3-based devices, respectively, with the thickness of the donor layer at 5 nm. In BHJ cells, we achieved much higher PCEs of 1.53% and 2.05% for Cu–Ce6Me3 :PC 70 BM and Ce6Me3 :PC 70 BM respectively, where both blending ratios were set to 1:8. The improvement on PCE in BHJ cells may be attributed to the better charge separation increase at the donor–acceptor interface.

Synthesis of Chl@Ti_(3)C_(2) composites as an anode material for lithium storage

Two-dimensional(2D)titanium carbide MXene Ti_(3)C_(2) has attracted significant research interest in energy storage applications.In this study,we prepared Chl@Ti_(3)C_(2) composites by simply mixing a chlorophyll derivative(e.g.,zinc methyl 3-devinyl-3-hydroxymethylpyropheophorbide a(Chl))and Ti_(3)C_(2) in tetrahydrofuran,where the Chl molecules were aggregated among the multi-layered Ti_(3)C_(2) MXene or on its surface,increasing the interlayer space of Ti_(3)C_(2).The as-prepared Chl@Ti_(3)C_(2) was employed as the anode material in the lithium-ion battery(LIB)with lithium metal as the cathode.The resulting LIB exhibited a higher reversible capacity and longer cycle performance than those of LIB based on pure Ti_(3)C_(2),and its specific discharge capacity continuously increased along with the increasing number of cycles,which can be attributed to the gradual activation of Chl@Ti_(3)C_(2) accompanied by the electrochemical reactions.The discharge capacity of 1 wt-%Chl@Ti_(3)C_(2) was recorded to be 325 mA·h·g^(-1) at the current density of 50 mA·g^(-1) with a Coulombic efficiency of 56% and a reversible discharge capacity of 173 mA·h·g^(-1) at the current density of 500 mA·g^(-1) after 800 cycles.This work provides a novel strategy for improving the energy storage performance of 2D MXene materials by expanding the layer distance with organic dye aggregates.