Hole transport layer (HTL) plays a critical role in perovskite solar cells (PSCs). We focus on the improvement of PSCs performance with MoS2 nanosheets as the anode buffer layer in the inverted photovoltaic structure. PSC with single MoS2 buffer layer shows poor performance in power conversion efficiency (PCE) and the long-term stability. By combination of MoS2and Poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA) as double-layer HTL, the PCE is improved to 18.47%, while the control device with PTAA alone shows a PCE of 14.48%. The same phenomenon is also found in 2D PSCs. For double-layer HTL devices, the PCE reaches 13.19%, and the corresponding PCE of the control group using PTAA alone is 10.13%. This significant improvement is attributed to the reduced interface resistance and improved hole extraction ability as shown by the electric impedance spectroscopy and fluorescence spectroscopy. In addition, the improved device exhibits better stability because the PCE still maintains 66% of the initial value after 500 hours of storage, which is higher than the 47% of the remaining PCE from device based on single PTAA or MoS2. Our results demonstrate the potential of polymer/inorganic nanomaterial as a double-layer buffer material for PSCs.

As part of our studies of chlorophyll-based sensitizers for solar energy applications, we recently synthesized two dyad panchromatic chromophores of chlorin-indoline (Chl-Ind) and chlorin-carotenoid (Chl-Car) conjugates aiming at the wider range of sunlight utilization. By comparing the absorption spectra of these dyad sensitizers in various solvents, we found that each chromophore unit in Chl-Ind showed drastic red-shift when measured in polar solvents, while the spectra of Chl-Car showed lesser solvent effects. To elucidate the origin of such solvatochromism by time dependent density functional theory (TD-DFT) calculations with molecular dynamics studies, we decided to compare the estimation results of TD-DFT/CAM-B3LYP (M06-2X and ωB97X-D) /6-31(d,p) using polarizable continuum model (H2O and THF) with the absorption spectra for Chl-Ind and Chl-Car, together with their sole chromophore units methyl trans-32-carboxy-pyropheophorbide-a (Chl), methyl ester of indoline dye D149 (Ind), and β-apo-8’-carotenoic acid ethyl ester (Car). The results revealed that the unusual peak shifts of Chl and Ind moieties in Chl-Ind dyad could be most properly reproduced at ωB97X-D density functionals. This is likely because ωB97X-D contains dispersion-corrected and long-range corrected functionals. The destabilized HOMO−1 is expected to contribute to the red-shift of Ind peak in the dyad. Our results would provide useful information for the selection of computational methods to anticipate spectral characteristics of covalently-linked multi-chromophores in advance.