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“Twisted” conjugated molecules as donor materials for efficient all-small-molecule organic solar cells processed with tetrahydrofuran
摘要： High-performance organic semiconductors that can be processed with environmentally benign solvents are highly desirable for printable optoelectronics. Herein, four acceptor–donor–acceptor conjugated molecules, i.e., DRTT-T, DRTT-R, DRTT-OR and DRTT, with 3-ethylrhodanine as acceptor terminal units and 2,5-bis(4,8-di(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b0]dithiophen-2-yl)thieno[3,2-b]thiophene derivatives as donor units were synthesized. 5-(2-Ethylhexyl)thiophen-2-yl, 2-ethylhexyl and 2-ethylhexyloxy were introduced at the b-positions of the central thieno[3,2-b]thiophene (TT) units in DRTT-T, DRTT-R and DRTT-OR, respectively, and unsubstituted TT was used as the central unit in DRTT. As revealed by density functional theory calculations, DRTT-OR and DRTT adopt an almost planar geometry, while DRTT-T and DRTT-R have “twisted” backbones due to the introduction of bulky substituents on TT units. Di?ering from DRTT-OR and DRTT which are only well soluble in chlorinated solvents such as chloroform, DRTT-T and DRTT-R also show high solubility in “greener” solvents, including toluene and tetrahydrofuran (THF). Non-fullerene small molecule (NFSM) organic solar cells (OSCs) were fabricated with these molecules as donor materials. The molecules (DRTT-T and DRTT-R) with twisted backbones displayed remarkably higher device performance compared to more planar ones (DRTT-OR and DRTT), attributed to the formation of ordered face-on microstructures with p–p stacking distances of 3.7–3.8 ?A and interpenetration networks of donor and acceptor components in the blend ?lms based on DRTT-T and DRTT-R. Most importantly, the power conversion e?ciencies (PCEs) of DRTT-T and DRTT-R based devices processed with THF reached 9.37% and 10.45%, respectively. This study demonstrates that “twisting” conjugated backbones is an appropriate strategy to design eco-friendly solvent processable organic semiconductors for high-e?ciency OSCs.
关键词： conjugated molecules,tetrahydrofuran,organic solar cells,donor materials,power conversion efficiencies
更新于2025-09-16 10:30:52
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Tetrahydrofuran as an Oxygen Donor Additive to Enhance Stability and Reproducibility of Perovskite Solar Cells Fabricated in High Relative Humidity (50%) Atmosphere
摘要： In sequential deposition method of lead-halide perovskite material, the PbI2 layer morphology plays an essential role in enhancing the power conversion efficiency (PCE) of the perovskite solar cell. However, humidity level affects the PbI2 and perovskite film morphology, resulting in defect sites and recombination centers on the surface and within the bulk of the perovskite solar cell. To address this, we report the incorporation of tetrahydrofuran (THF) additive in PbI2-DMF precursor solution, to improve the quality of PbI2 thin film and to prevent the water interaction directly with PbI2 under high humidity environment. The O-donor THF interacts with PbI2 resulting in the homogeneous, dense and pinhole-free layer as compared to PbI2 layer without additive. The Perovskite layer so obtained from pinhole-free PbI2 layer is compact and smooth resulting in a significant reduction of defects/traps. The device fabricated with modified perovskite ~ 50% humidity atmosphere, resulted in 15% efficiency with high reproducibility. Moreover, the THF modified non-encapsulated perovskite device retains its 80% PCE after exposing to 50% relative humidity for 20 days. Our result demonstrates the strategy to fabricate perovskite solar cells with reproducible efficiency in high humidity atmosphere viable for large-scale production.
关键词： two-step deposition,perovskite solar cells,high humidity,long-term stability,pinhole-free PbI2,tetrahydrofuran (THF)
更新于2025-09-11 14:15:04
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Facile Preparation of Functional Group Gradient Surfaces by Desorption and <i>Re</i> -Adsorption of Alkanethiols on Gold
摘要： Many organisms live in various stimuli-responsive milieus of signaling components in gradient forms which are known to be closely related to biological phenomena including embryonic development, wound repair, and tumor metastasis. In addition, the physicochemical properties of gradient surfaces, i.e., a continuous spatial variation of gradient components, enable various types of biological/biochemical research such as cell proliferation/migration and tissue engineering. Various techniques have been reported for the preparation of gradient surfaces, including laminar flow mixing in microfluidic channels, cross-diffusion of alkanethiols, microfluidic permeation printing, oblique deposition and template coating, controlled polymerization on substrates, and controlled UV irradiation on photo-responsive substrates. Previously, we reported a simple method for the generation of multi-component gradient surfaces on self-assembled monolayers (SAMs) on gold. The monolayers consisted of quinone derivatives which reacted with reducing agents in a predictable manner to produce amine gradient surfaces. Recently, desorption and re-adsorption-based methods on SAMs have gained attention, in which alkanethiolates on gold surfaces were desorbed in order to provide an empty space gradient, following which other types of alkanethiols filled up the empty space, leading to an end group gradient of alkanethiolates. For example, Kim et al. reported a simple and flexible method for preparing cell adhesion ligand patterns on SAMs by using a laser beam equipped in a matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometer. Similarly, Meyyappan et al. demonstrated that a surface gradient can be achieved by irradiating a focused laser beam on SAMs with subsequent re-adsorption of a second alkanethiol. Fioravanti et al. reported on a new method to fabricate surface chemical gradients of alkanethiols through combining reductive electrochemical desorption and partial re-adsorption of alkanethiolates. Recently, we found that tetrahydrofuran (THF) highly compromises the stability of SAMs on gold, and thus induces unusually fast exchange of alkanethiolates of SAMs with other alkanethiols in the solution. In this study, we harnessed this desorption capability of THF for the preparation of functional group gradient surfaces. In our strategy, a monolayer of alkanethiolates was exposed to THF in a time-dependent manner followed by immersion in a solution of other functional group-terminated alkanethiols, leading to functional group gradient surfaces. The functional group then played a role of a chemical handle to conjugate various functional molecules for the formation of gradients of those components.
关键词： Gradient surfaces,Alkanethiols,Desorption,Self-assembled monolayers,Tetrahydrofuran
更新于2025-09-09 09:28:46