Self-assembled donor-acceptor hole contacts for inverted perovskite solar cells with an efficiency approaching 22%: The impact of anchoring groups

Self-assembled molecules(SAMs) have shown great potential in replacing bulk charge selective contact layers in high-performance perovskite solar cells(PSCs) due to their low material consumption and simple processing. Herein, we design and synthesize a series of donor-acceptor(D-A) type SAMs(MPA-BTCA, MPA-BT-BA, and MPA-BT-RA, where MPA is 4-methoxy-N-(4-methoxyphenyl)-N-phenylaniline;BT is benzo[c][1,2,5]-thiadiazole;CA is 2-cyanoacrylic acid, BA is benzoic acid, RA is rhodanine-3-propionic acid) with distinct anchoring groups, which show dramatically different properties. MPA-BTCA with CA anchoring groups exhibited stronger dipole moments and formed a homogeneous monolayer on the indium tin oxide(ITO) surface by adopting an upstanding self-assembling mode. However, the MPA-BT-RA molecules tend to aggregate severely in solid state due to the sp~3 hybridization of the carbon atom on the RA group, which is not favorable for achieving a long-range ordered self-assembled layer.Consequently, benefiting from high dipole moment, as well as dense and uniform self-assembled film,the device based on MPA-BT-CA yielded a remarkable power conversion efficiency(PCE) of 21.81%.Encouragingly, an impressive PCE approaching 20% can still be obtained for the MPA-BT-CA-based PSCs as the device area is increased to 0.80 cm^(2). Our work sheds light on the design principles for developing hole selecting SAMs, which will pave a way for realizing highly efficient, flexible, and large-area PSCs.

Effects of anchoring groups on perylenemonoimide-based sensitizers for p-type dye-sensitized solar cells and photoelectrochemical cells

In this work, two new dyes YK-1 and YK-2 with carboxylic acid and hydroxamic acid as anchoring groups,respectively, in combination with diphenylamine as donor and perylenemonoimide as acceptor were synthesized and applied in p-type dye-sensitized solar cells（p-DSCs） and dye-sensitized photoelectrochemical cells（PEC）. The results showed that the sensitizer（YK-1） based on carboxylic acid displayed a higher conversion efficiency of 0.064% under AM 1.5 solar conditions in p-DSCs. However, it was interesting that the hydroxamic acid based sensitizer（YK-2） on Ni O photocathode displayed better performance in a hydrophilic environment over a broad p H range under visible-light irradiation because of a versatile covalent attachment to Ni O surfaces. This may be ascribed to hydroxamic acid anchors, which have more sites interacting with the surface of Ni O in aqueous solution. This study demonstrates that YK-2 containing hydroxamic acid anchoring group is a promising candidate to achieve highly efficient and stable activity for dye-sensitized PEC system.

Unravelling the bottleneck of phosphonic acid anchoring groups aiming toward enhancing the stability and efficiency of mesoscopic solar cells

Novel near-infrared sensitizers with different anchoring groups aiming toward improved stability and efficiency of dye-sensitized solar cells were synthesized. Adsorption of these dyes on the mesoporous TiO_(2) surface revealed the dye adsorption rate of –CH=CH–COOH (SQ-139)>–CH=C(CN)COOH (SQ-140)>–PO_(3)H_(2) (SQ-143)>–CH=C(CN)PO_(3)H_(2) (SQ-148)>–CH=C(CN)PO_(3)H–C_(2)H_(5) (SQ-157)>–PO_(3)H–C_(2)H_(5) (SQ-151)> –CH=CH–COOH(–PO_(3)H_(2)) (SQ-162). The binding strength of these dyes on mesoporous TiO_(2) as investigated by dye desorption studies follows SQ-162>SQ-143>SQ-148>SQ-139≫SQ-157~SQ-151≫SQ-140 order. The acrylic acid anchoring group was demonstrated to be an optimum functional group owing to its fast dye adsorption rate and better binding strength on TiO_(2) along with good photoconversion efficiency. Results of dye binding on TiO_(2) surface demonstrated that SQ-162 bearing double anchoring groups of phosphonic and acrylic acid exhibited>550 times stronger binding as compared to dye SQ-140 having cyanoacrylic acid anchoring group. SQ-140 exhibited the best photovoltaic performance with photon harvesting mainly in the far-red to near-infrared wavelength region having short circuit current density, open-circuit voltage and fill factor of 14.28 mA·cm^(–2), 0.64 V and 0.65, respectively, giving the power conversion efficiency of 5.95%. Thus, dye SQ-162 not only solved the problem of very poor efficiency of dye bearing only phosphonic acid while maintaining the extremely high binding strength opening the path for the design and development of novel near-infrared dyes with improved efficiency and stability by further increasing the π-conjugation.

New tetrazole-based organic dyes for dye-sensitized solar cells

A series of new metal-free organic dyes that contain donors with triphenylamine or its derivatives and tetrazole-based acceptors were synthesized and characterized by photophysical, electrochemical, and the- oretical computational methods. They were applied in nanocrystalline TiO2 solar cells （DSSCs）. It is found that the introduction of diphenylamine units as antennas in the as-synthesized dyes could improve photo- voltaic performance compared with phenothiazine and carbazole units as antennas in DSSCs. The dye with （2H-tetrazol-5-yl） acrylonitrile electron acceptor also displayed the highest solar-to-electrical energy conver- sion efficiency.

Design of artificial biomimetic channels with Na^(+)permeation rate and selectivity potentially outperforming the natural sodium channel

Artificial ion channels that enable high-efficiency ion transport have important implications in nanofluidics and biomedical applications such as drug delivery.Herein,we show a simulation-based chemical design of a biomimetic sodium channel that possesses permeation rate and selectivity potentially higher than those of the state-of-the-art natural vertebrate voltage-gated sodium channels.Importantly,our theoretical findings have undergone empirical testing,aligning well with the Arrhenius law as derived from a diverse range of experimental results.The high-efficiency ion transport is achieved by anchoring the carboxylate functional groups within the channel filter.A key chemical guiding principle underlying the ion channel design is that the free-energy barrier for the Na^(+)passage across the channel should be comparable to typical thermal energy at room temperature.With the implementation of the chemical design,we found that the relatively low free-energy barrier can be attributed to the compensation effect of the carboxylate groups to the partially lost oxygen shell of the ion within the ion channel,as well as to the consonant vibration of the ions inside and outside the channel.This mechanistic understanding brings new insight,at the molecular level,into the high-efficiency ion transport across the designed membrane channels.The proof of principle achieved from the simulations will stimulate future experimental confirmation and potential applications of the high-performance artificial channels in nanofluidics and in bioinspired iontronics.

SalenZn-bridged D-π-A Dyes For Dye-Sensitized Solar Cells

A series of SalenZn based dyes with triphenylamine derivatives as the donor,benzoic acid as the acceptor,and coplanar Salen complexes as the spacer have been designed and synthesized for dye-sensitized solar cells.The ab-sorption,electrochemical,and photovoltaic properties for all sensitizers have been systematically investigated.When the tail length of the alkyl substituents is increased from C-0 to C-8 on the donor part,the efficiency of its DSSC augments evidently.It is found that the incorporation of bis-carboxyl groups instead of the single carboxyl group as anchoring groups induces a remarkable enhancement of the electron injection efficiency from the excited dyes to the TiO_(2)semiconductor and generates higher electron density and voltage.