Fu-Ling Guo

Mesoporous TiO2 Yolk-Shell Microspheres for Dye-sensitized Solar Cells with a High Efficiency Exceeding 11%.

Yolk-shell TiO2 microspheres were synthesized via a one-pot template-free solvothermal method building on the aldol condensation reaction of acetylacetone. This unique structure shows superior light scattering ability resulting in power conversion efficiency as high as 11%. This work provided a new synthesis system for TiO2 microspheres from solid to hollow and a novel material platform for high performance solar cells.

Superior Light-Harvesting Heteroleptic Ruthenium(II) Complexes with Electron-Donating Antennas for High Performance Dye-Sensitized Solar Cells

Three heteroleptic polypyridyl ruthenium complexes, RC-41, RC-42, and RC-43, with efficient electron-donating antennas in the ancillary ligands were designed, synthesized, and characterized as sensitizers for dye-sensitized solar cell. All the RC dye sensitizers showed remarkable light-harvesting capacity and broadened absorption range. Significantly, RC-43 obtained the lower energy metal-ligand charge transfer (MLCT) band peaked at 557 nm with a high molar extinction coefficient of 27 400 M(-1) cm(-1). In conjunction with TiO2 photoanode of submicrospheres and iodide-based electrolytes, the DSSCs sensitizing with the RC sensitizers, achieved impressively high short-circuit current density (19.04 mA cm(-2) for RC-41, 19.83 mA cm(-2) for RC-42, and 20.21 mA cm(-2) for RC-43) and power conversion efficiency (10.07% for RC-41, 10.52% for RC-42, and 10.78% for RC-43). The superior performances of RC dye sensitizers were attributed to the enhanced light-harvesting capacity and incident-photon-to-current efficiency (IPCE) caused by the introduction of electron-donating antennas in the ancillary ligands. The interfacial charge recombination/regeneration kinetics and electron lifetime were further evaluated by the electrochemical impedance spectroscopy (EIS) and transient absorption spectroscopy (TAS). These data decisively revealed the dependences on the photovoltaic performance of ruthenium sensitizers incorporating electron-donating antennas.

Tetraphenylmethane-Arylamine Hole-Transporting Materials for Perovskite Solar Cells

A new class of hole-transporting materials (HTM) containing tetraphenylmethane (TPM) core have been developed. After thermal, charge carrier mobility, and contact angle tests, it was found that TPA-TPM (TPA: arylamine derivates side group) showed higher glass-transition temperature and larger water-contact angle than spiro-OMeTAD with comparable hole mobility. Photoluminescence and impedance spectroscopy studies indicate that TPA-TPMs hole-extraction ability is comparable to that of spiro-OMeTAD. SEM and AFM results suggest that TPA-TPM has a smooth surface. When TPA-TPM is used in mesoscopic perovskite solar cells, power conversion efficiency comparable to that of spiro-OMeTAD is achieved. Notably, the perovskite solar cells employing TPA-TPM show better long-term stability than that of spiro-OMeTAD. Moreover, TPA-TPM can be prepared from relatively inexpensive raw materials with a facile synthetic route. The results demonstrate that TPM-arylamines are a new class of HTMs for efficient and stable perovskite solar cells.

Diketopyrrolopyrrole or benzodithiophene-arylamine small-molecule hole transporting materials for stable perovskite solar cells

Two simple small-molecular arylamine derivatives 4-methoxy-N-(4-methoxyphenyl)-N-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)aniline (OMeTPA-DPP) and 4,4′-(4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)bis(N,N-bis(4-methoxyphenyl)aniline) (OMeTPA-BDT) linked with diketopyrrolopyrrole or benzodithiophene moieties have been synthesized. The new compounds show better thermal stability than spiro-OMeTAD. The steady-state and time-resolved photoluminescence demonstrate that the new compounds have good hole extraction ability. The perovskite solar cells employing OMeTPA-BDT show a comparable power conversion efficiency with that of spiro-OMeTAD. After more than 200 hours of aging under one sun illumination, the residual efficiencies of the PSCs based on OMeTPA-DPP, OMeTPA-BDT and spiro-OMeTAD are 8.69%, 11.15% and 9.08%, respectively. The results demonstrate that the newly-developed compounds can act as efficient hole transporting materials for stable perovskite solar cells.

Broad spectral-response organic D–A–π–A sensitizer with pyridine-diketopyrrolopyrrole unit for dye-sensitized solar cells

In this work, four D–A–π–A sensitizers PDPP-I–IV based on pyridine-flanked DPP moieties (PDPP) were designed and synthesized for dye-sensitized solar cells. Remarkably, the incorporated electron-withdrawing unit of pyridine-flanked DPP improves the light-harvesting ability and modifies the electrochemical and absorption properties, generating a broader IPCE wavelength responding region. The electrochemical experiments and time-resolved photoluminescence measurements indicate the ability of electron-injection into the TiO2 conductive band from the excited sensitizer. The transient absorption spectra were measured to investigate the feasibility of the dynamics for oxidized-state sensitizer regeneration. The IPCE spectra demonstrate the broad spectral response region of these sensitizers. Especially, the IPCE of PDPP-III reached the near infrared (NIR) region (>800 nm) with the highest short-circuit current of 16.17 mA cm−2 in these sensitizers. Furthermore, the electrochemical impedance spectroscopy (EIS) experiments suggest that the electron-lifetime and charge recombination resistance increased when attaching the stereo substituted groups (R2) on the PDPP moiety, resulting in a higher open-circuit voltage (Voc). It can be found that PDPP-II based DSSCs with liquid electrolyte exhibited the highest Voc (523 mV) and power conversion efficiency (PCE) of 5.26%.