Materials with nonlinear optical properties have significant applications in nuclear science, biophysics, medicine, chemical dynamics, solid physics & materials science. We show how π bridges, donors & acceptors can be reconfigured to improve optical properties.

Three dimensional (3D) acceptor‐donor‐acceptor (A−D‐A) type small molecules (M1, M2, M3 and M4) are theoretically investigated for optoelectronic properties. The designed molecules contain spirobifluorene as core unit linked with end capped acceptors through four four thieno‐[3,2‐b]Thiophene (TT) units. The end capped acceptors are (3‐methyl‐2‐thioxothiazolidin‐4‐one) (M1), 2‐(2‐ethylidene‐5,6‐difluoro‐3‐oxo‐2,3‐dihydroinden‐1‐ylidene)malononitrile (M2), 2‐(3‐ethyl‐4‐oxothiazolidin‐2‐ylidine)malononitrile (M3) and 2‐(2‐ethylidene‐5,6‐dicyano‐3‐oxo‐2,3‐dihydroinden‐1‐ylidene)malononitrile (M4). The photovoltaic parameters of the designed molecules are compared with the recently reported reference compound R. Among all designed molecules, M4 is a low energy gap material (2.28 eV), broad absorption which is attributed to excellent communication between strong electron withdrawing end capped acceptors through extended conjugation. All newly designed molecules have lower binding energy as compared to reference molecule R which results in higher exciton dissociation in excited state. The reorganization energy calculations indicate good charge transfer ability of the designed molecules. M4 shows the lowest λe (0.0022) value with respect to the reference molecule R (0.034) which signifies its enhanced electronic transport behavior. The calculated open circuit voltages (Voc) ranges from 1.97 to 2.36 eV, 2.11 to 2.49 eV and 1.9 eV to 2.28 eV with respect to three different well known donor materials PTB7‐Th, PBDB−T and P3HT, respectively.

The increasing demand of energy expedited the development of efficient photovoltaic materials.Herein, five push‐pull donor materials (D1‐D5) having N,N‐diethylaniline as donor moiety and rhodanine‐3‐acetic as acceptor group are designed to be used as donor molecules in organic solar cells (OSCs). The bridging core modification of recently synthesized MR3 molecule (reference R) has been made with different π‐spacers namely thiazole (B1), thieno[3,2‐b]thiophene (B2), thiazolo[5,4‐d] thiazole (B3), 2‐(thiophen‐2‐yl)thiophene (B4) and 5‐(thiazol‐5yl)thiazole (B5). The structure–property relationship is studied and influence of bridging core modifications on photovoltaic, photophysical and electronic properties of D1‐D5 are calculated and compared with reference R.The DFT and TDDFT calculations have been performed for the estimation of frontier molecular orbital (FMO) analysis, density of states (DOS) graphs, reorganization energies of electron and hole, open circuit voltage, photophysical characteristics, transition density matrix (TDM) surfaces and charge transfer analysis.Designed molecules exhibit better and comparable optoelectronic properties than synthesized reference molecules. Among all investigated molecules, D5 is proven as best candidate for OSCs application due to its promising photovoltaic properties including lowest band gap (2.24 eV), small electron mobility (λe=0.0056 eV), small hole mobility (λh=0.0046 eV), low binding energy (Eb=0.21 eV), highest λmax values 610.76 nm (in gas) 670.22 nm (in acetonitrile) and high open circuit voltage (Voc=1.17 V) with respect to HOMOdonor–LUMOPC61BM. This theoretical framework demonstrates that bridging core modification is a simple and effective alternative strategy to achieve the desirable optoelectronic properties. Furthermore, conceptualized molecules are superior and thus are recommended to experimentalist for out‐looking future developments of highly efficient solar cells.

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The development of organic electron acceptor materials is one of the key factors for realizing high-performance organic solar cells (OSCs). Nonfullerene electron acceptors, compared to traditional fullerene acceptor materials, have gained much impetus owing to their better optoelectronic tunabilities and lower cost, as well as higher stability. Therefore, 5 three-dimensional (3D) cross-shaped acceptor materials having a spirobifullerene core flanked with 2,1,3-benzothiadiazole are designed from a recently synthesized highly efficient acceptor molecule SF(BR) 4 and are investigated in detail with regard to their use as acceptor molecules in OSCs. The density functional theory (DFT) and time-dependent DFT (TDDFT) calculations have been performed for the estimation of frontier molecular orbital (FMO) analysis, density of states analysis, reorganization energies of electron and hole, dipole moment, opencircuit voltage, photo-physical characteristics, and transition density matrix analysis. In addition, the structure-property relationship is studied, and the influence of end-capped acceptor modifications on photovoltaic, photo-physical, and electronic properties of newly selected molecules (H1-H5) is calculated and compared with reference (R) acceptor molecule SF(BR) 4. The structural tailoring at terminals was found to effectively tune the FMO band gap, energy levels, absorption spectra, open-circuit voltage, reorganization energy, and binding energy value in selected molecules H1 to H5. The 3D cross-shaped molecules H1 to H5 suppress the intermolecular aggregation in PTB7-Th blend, which leads to high efficiency of acceptor material H1 to H5 in OSCs. Consequently, better optoelectronic properties are achieved from designed molecules H1 to H5. It is proposed that the conceptualized molecules are superior than highly efficient spirobifullerene core-based SF(BR) 4 acceptor molecules and, thus, are recommended to experiments for future developments of highly efficient solar cells.

Gas sensing materials have been widely explored recently owing to their versatile environmental and agriculture monitoring applications. The present study advocates the electronic response of Zn-decorated inorganic B 12 P 12 nanoclusters to CO 2 gas. Herein, a series of systems CO 2 −Zn−B 12 P 12 (E1−E4) are designed by adsorption of CO 2 on Zn-decorated B 12 P 12 nanoclusters, and their electronic properties are explored by density functional theory. Initially, placement of Zn on B 12 P 12 delivers four geometries named as D1−D4, with adsorption energy values of −57.12, −22.94, −21.03, and −14.07 kJ/mol, respectively, and CO 2 adsorption on a pure B 12 P 12 nanocage delivers one geometry with an adsorption energy of −4.88 kJ/mol. However, the interaction of CO 2 with D1−D4 systems confers four geometries named as E1 (E ad = −75.12 kJ/mol), E2 (E ad = −25.89 kJ/mol), E3 (E ad = −42.43 kJ/mol), and E4 (E ad = −28.73 kJ/mol). Various electronic parameters such as dipole moment, molecular electrostatic potential analysis, frontier molecular orbital analysis, Q NBO , global descriptor of reactivity, and density of states are also estimated in order to understand the unique interaction mechanism. The results of these analyses suggested that Zn decoration on B 12 P 12 significantly favors CO 2 gas adsorption, and a maximum charge separation is also noted when CO 2 is adsorbed on the Zn−B 12 P 12 nanocages. Therefore, the Zn-decorated B 12 P 12 nanocages are considered as potential candidates for application in CO 2 sensors.

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