Carbazole-substituted NP-based derivative as hole transporting material for highly efficient perovskite solar cells.

Three new organic hole transport materials (HTMs), 2, 3 and 4, are designed with NP-core along with bis(4-methoxyphenyl)amine, p-methoxytriphenylamine, and 9-p-tolyl-9H-carbazole as side group on the basis of reported HTM NP2 (1), respectively. For isolated molecules, frontier molecular orbitals, absorption and emission spectra, and hole mobility are evaluated by density functional theory (DFT) and molecular dynamics simulations. In addition, the following properties, hydrophobility, solubility, and glass transition temperatures (Tg), related with the overall performance of devices are also calculated. The HTM@CH3NH3PbI3 adsorbed system is investigated to consider the effect of interfacial properties between HTM and CH3NH3PbI3 on HTM properties. Our theoretical results indicate that the new designed molecule 4 has better properties than 1. More importantly, 1 has been fabricated in perovskite solar cells (PSCs) as a HTM with the power conversion efficiency of 16.4%. It is reasonable to infer that the new designed molecules would be potential candidates.

Rational design of D-π-A organic dyes to prevent "trade off" effect in dye-sensitized solar cells.

It is an easy task to simulate the spectrum properties for the organic dyes applied in dye-sensitized solar cells (DSSCs) if the suitable method is chosen. However, it is still difficult to quantitatively determine the overall performance for them. In this work, the short-circuit photocurrent density (JSC) and open circuit photovoltage (VOC) are quantitatively calculated by combination of the density functional theory and first principle for DSSCs based on four different organic dyes, 2-((4'-((4-(bis(4-methoxyphenyl)amino)phenyl)diazenyl)biphenyl-4-yl)methylene)but-3-ynoic acid (1), 2-((5-(4-((4-(bis(4-methoxyphenyl)amino)phenyl)diazenyl)phenyl)thiophen-2-yl)methylene)but-3-ynoic acid (2), 3-(7-(4-((4-(bis(4-methoxyphenyl)amino)phenyl)diazenyl)-4H-cyclopenta[2,1-b:3,4-b']-dithiophene)-2-cyanoacrylic acid (3), and 3-(7-(4-((4-(bis(4-methoxyphenyl)amino)phenyl)diazenyl)phenyl)-2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-cyanoacrylic acid (4), in which the triarylamine is donor and the cyanoacrylic acid is acceptor along with variable π group. The 3 and 4 are new theoretically designed organic dyes on the basis of 1 and 2 with different electron-rich group as π group. Both JSC and VOC of 3 and 4 are improved as compared with those of 1 and 2, which breaks the normal "trade-off" rule. As a result, the power conversion efficiency (PCE) of 3 and 4 is improved, especially for 3. The aggregation effect is also considered to evaluate the overall performance, which is favorable to further enhance the reliability of theoretical design.