Designing of benzodithiophene core-based small molecular acceptors for efficient non-fullerene organic solar cells.

Perovskite solar cells have gained immense interest from researchers owing to their good photophysical properties, low-cost production, and high power conversion efficiencies. Hole transport materials (HTMs) play a dominant role in enhancing the power conversion efficiencies (PCEs) and long diffusion length of holes and electrons in perovskite solar cells. In hole transport materials, modification of π-linkers has proved to be an efficient approach for enhancing the overall PCE of perovskite solar cells. In this work, π-linker modification of a recently synthesized H-Bi molecule (R) is achieved with novel π-linkers. After structural modifications, ten novel HTMs (HB1-HB10) with a D-π-D backbone are obtained. The structure-property relationship, and optoelectronic and photovoltaic characteristics of these newly designed hole transport materials are examined comprehensively and compared with reference molecules. In addition, different geometric parameters are also examined with the assistance of density functional theory (DFT) and time-dependent DFT. All the designed molecules exhibit narrow HOMO-LUMO energy gaps (Eg =2.82-2.99 eV) compared with the R molecule (Eg =3.05 eV). The designed molecules express redshifting in their absorption spectra with low values of excitation energy, which in return offer high power conversion efficiencies. Further, density of states and molecular electrostatic potential analysis is performed to locate the different charge sites in the molecules. The reorganizational energies of holes and electrons are found to have good values, suggesting that these novel designed molecules are efficient hole transport materials for perovskite solar cells. In addition, the low binding energy values of the designed molecules (compared with R) offer high current charge density. Finally, complex study of HB9:PC61 BM is also undertaken to understand the charge transfer between the molecules of the complex. The results of all analyses advocate that these novel designed HTMs are promising candidates for the construction of future high-performance perovskite solar cells.

How Does Bridging Core Modification Alter the Photovoltaic Characteristics of Triphenylamine-Based Hole Transport Materials? Theoretical Understanding and Prediction

Hole transport materials (HTMs), especially dopant-free hole transport materials, are getting attention in enhancing the power conversion efficiencies and stabilities of organic solar cells (OSCs). Herein, we have designed efficient dopant-free HTMs (DM1–DM5) from an outstanding synthetic DFM molecule (having 20.6% PCE). Photo-physical, photovoltaic, optoelectronic and structural-property relationship of newly designed molecules are extensively studied and compared with DFM (R). Density functional theory (DFT) and time-dependent-density functional theory (TD-DFT) have been employed to investigate the alignment of frontier molecular orbitals (FMOs), optical properties, density of states along with transition density matrix, binding and excitation energy, reorganizational energies and for open-circuit voltages of all newly designed molecules. Red-shifting in absorption spectrum offers high power conversion efficiencies, and our tailored molecules exhibit red-shifting in absorption spectrum (λmax = 391–429 nm) as compared to R (λmax = 396 nm). In addition, our all designed molecules expressed better hole transport ability (λh = 0.0056–0.0089 eV) as compared to R (λh = 0.0101 eV). Similarly, DM1–DM5 disclosed narrow HOMO–LUMO energy gap which causes maximum charge transfer from excited HOMO to excited LUMO. The theoretical study of DM3/PC61BM and DM3/Y6 complexes is also performed in order to understand the shifting of charge between donor and acceptor molecules. Results of all analysis clearly show the efficient designing of dopant-free (DM1–DM5) molecules and their possible potential to fabricate a high performance and stable organic solar cells devices. Therefore, the theoretical proposed molecules are recommended to experimentalists for future highly efficient organic solar cells.

Efficient designing of triphenylamine-based hole transport materials with outstanding photovoltaic characteristics for organic solar cells

First theoretical framework of Z-shaped acceptor materials with fused-chrysene core for high performance organic solar cells.

Herein, we have designed four small molecular donors (SMDs) with Donor–Acceptor–Acceptor (D–A–A) backbone having different acceptor units for highly efficient organic solar cells (OSCs). The specif...

Designing of near-infrared sensitive asymmetric small molecular donors for high-efficiency organic solar cells

Non fullerene small acceptor molecules in organic photovoltaics are proven beneficial than the traditional fullerene based acceptors for their fine contribution in organic solar cells. Researchers are constantly doing efforts for designing novel acceptor materials with promising photovoltaic properties. Designing of novel molecules by end-capped modifications is a convenient strategy to obtain high efficiency acceptor molecules for OSCs. Herein, we studied optoelectronic characteristics of five novel acceptor–donor–core–donor–acceptor configured small acceptor molecules (S1–S5) after end-capped modifications of recently synthesized DF-PCIC molecule. Designed molecules S1–S5 consist of 1,4-difluorobenzene (as central core), 4,4-bis(2-ethylhexyl)-2,6-dimethyl-4H-cyclopenta[1,2-b:5,4-b′]dithiophene as donor which directly attached with different end-capped acceptors. The electronic and optical properties of newly designed (S1–S5) molecules are examined and compared with reference molecule with the aid of DFT and TD-DFT. Certain key parameters like frontier molecular orbitals analysis, density of states, dipole moment, binding energy along with transition density matrix, excitation energy, charge mobility, absorption maxima and charge transfer analysis have been performed in order to explore the photo-physical, optoelectronic and photovoltaic properties of designed and reference molecule. Out of newly designed structures, S4 displayed lowest energy band-gap (2.25 eV) with red-shifting in absorption spectrum (λmax = 712.43 nm) in chloroform which disclosed the perfect relationship between end-capped acceptor with large electron withdrawing character through extended conjugation. Similarly, S1 exhibited highest value (1.53 V) of open circuit voltage (Voc) with respect to PTB7-Th donor material owing to lower values of λe. Designed molecules exhibit better electron and hole mobility as compared to reference molecule R. All molecules express better absorption maximum, open circuit voltage, low excitation energies, comparable binding energies, large dipole moment and efficient electron and hole transport as compared to reference molecules. So, results these parameters suggest that end-capped modification is a convenient strategy in order to enhance the efficiency of OSCs. Therefore, conceptualized molecules are recommended to experimentalist for out-looking future developments of highly efficient solar cells.

Molecular engineering of A–D–C–D–A configured small molecular acceptors (SMAs) with promising photovoltaic properties for high-efficiency fullerene-free organic solar cells

Rafia Fatima

Papers

Molecular engineering of A–D–C–D–A configured small molecular acceptors (SMAs) with promising photovoltaic properties for high-efficiency fullerene-free organic solar cells

Efficient designing of triphenylamine-based hole transport materials with outstanding photovoltaic characteristics for organic solar cells

Designing of near-infrared sensitive asymmetric small molecular donors for high-efficiency organic solar cells

Molecular designing of high-performance 3D star-shaped electron acceptors containing a truxene core for nonfullerene organic solar cells