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Using our recently developed theoretical inverse-design method (PooMa) a new series of branched oligothiophene molecules for photovoltaic donors are designed. PooMa uses a genetic algorithm to screen a huge pool of compounds combined with a fast electronic-structure method (Density-Functional Tight-Binding, DFTB) with reasonable accuracy. Here, we apply this inverse-design method to identify a set of 20 branched oligothiophene systems with promisingly high efficiencies by using a Quantitative Structure Property Relation (QSPR) model based on five electronic descriptors that describe the performance of organic solar cells. We consider a pool of oligomers that are modified by attaching to each of 7 different sites one out of 22 functional groups, i.e., a pool of 227 ≈ 2.5×109 molecules. Subsequently, density-functional-theory (DFT) and Time-Dependent-DFT (TD-DFT) calculations in the gas phase with a 6-31G(d,p) basis set have been carried through to give further information on the suggested oligomers. Bulk-heterojunction photovoltaic cells were designed with the suggested oligothiophenes as donors and Phenyl-C61-butyric acid methyl (PCBM) derivatives as acceptors. Conversion efficiencies of the designed photovoltaic cells were examined with the Scharber diagram model.

Small organic conjugated molecules are key elements for low-cost photovoltaic devices. One example is cyanopyridone molecules. By modifying these molecules, for instance through optimally chosen functional groups attached to the backbone, their properties can be improved. However, the very large number of possible modifications makes it difficult to identify the best performing molecules. In the present work, we have used a computational inverse-design approach (PooMa) to identify the positions and types of functional groups attached to a modified cyanopyridone that lead to the best performance in solar-energy harvesting. A QSPR model based on five electronic descriptors has been used to determine the properties of solar cells. Our approach uses a genetic algorithm to search the chemical space containing 184 (104,976) substituted cyanopyridone systems and predicts out of those the best 20 molecules with optimal performance efficiencies (PCE). PooMa uses the Density-Functional Tight-Binding (DFTB) method for calculating the electronic properties. DFTB is a fast method with acceptable accuracy and, therefore, can be used on a normal desktop without expensive hard- or software. In order to get further information about our suggested systems, a DFT method and its derivative TD-DFT are applied.

Three π-A-porphyrins containing long alkoxyl chains attached to the ortho position of phenyl ring and a phenyl carboxylate acid or acrylic acid at the meso position of porphyrin were synthesized. All compounds were characterized by 1H NMR and mass spectrometry. Optical and electrochemical properties were also obtained. The photovoltaic properties of these π-A-porphyrins were examined for the first time and sensitizers N-1 and N-3 achieved comparable light to electricity conversion efficiencies: 3.94% for N-1 and 4.14% for N-3. However, preparation of N-1 required simple and cost-effective synthesis which made it a promising candidate for the future practical DSSC applications. The low efficiency conversion of N-2 was well explained by the amount of dye loading, IPCE and EIS.

A series of novel zinc porphyrins which are featured with a donor–π–acceptor structure have been synthesized for use in the dye-sensitized solar cells. Various diarylamine moiety, such as diphenylamine, iminodibenzyl or iminostilbene, is introduced at porphyrin meso position as an electron donating group. The cell fabricated with the iminodibenzyl-substituted porphyrin sensitizer yields a short circuit photocurrent density of 9.68 mA/cm2, an open-circuit voltage of 740 mV, and a fill factor of 73.48%, corresponding to an overall conversion efficiency (η) up to 5.26%, which is greater than those obtained by diphenylamine- and iminostilbene-substituted porphyrin-sensitized solar cells (η = 4.05% and 2.62%, respectively). The theoretical studies reveal that the iminodibenzyl donor has the strongest electron donating ability among all three diarylamine substituents employed, which is believed to play a significant role in influencing the photovoltaic properties of these sensitizer-based solar cells.