Advanced High-Throughput Rational Design of Porphyrin-Sensitized Solar Cells Using Interpretable Machine Learning.

Accurately predicting the power conversion efficiency (PCE) in dye-sensitized solar cells (DSSCs) represents a crucial challenge, one that is pivotal for the high throughput rational design and screening of promising dye sensitizers. This study presents precise, predictive, and interpretable machine learning (ML) models specifically designed for Zn-porphyrin-sensitized solar cells. The model leverages theoretically computable, effective, and reusable molecular descriptors (MDs) to address this challenge. The models achieve excellent performance on a "blind test" of 17 newly designed cells, with a mean absolute error (MAE) of 1.02%. Notably, 10 dyes are predicted within a 1% error margin. These results validate the ML models and their importance in exploring uncharted chemical spaces of Zn-porphyrins. SHAP analysis identifies crucial MDs that align well with experimental observations, providing valuable chemical guidelines for the rational design of dyes in DSSCs. These predictive ML models enable efficient in silico screening, significantly reducing analysis time for photovoltaic cells. Promising Zn-porphyrin-based dyes with exceptional PCE are identified, facilitating high-throughput virtual screening. The prediction tool is publicly accessible at https://ai-meta.chem.ncu.edu.tw/dsc-meta.

The influence of electron injection and charge recombination kinetics on the performance of porphyrin-sensitized solar cells: effects of the 4-tert-butylpyridine additive.

The effects of the 4-tert-butylpyridine (TBP) additive in the electrolyte on photovoltaic performance of two push-pull porphyrin sensitizers (YD12 and YD12CN) were examined. Addition of TBP significantly increased the open-circuit voltage (VOC) for YD12 (from 550 to 729 mV) but it was to a lesser extent for YD12CN (from 544 to 636 mV); adding TBP also had the effect of reducing the short-circuit current density (JSC) slightly for YD12 (from 17.65 to 17.19 mA cm(-2)) but it led to a significant reduction for YD12CN (from 16.45 to 9.78 mA cm(-2)). The resulting power conversion efficiencies of the YD12 devices increase from 6.2% to 8.5% whereas those of the YD12CN devices decrease from 5.8% to 4.5%. Based on measurements of temporally resolved photoelectric transients of the devices and femtosecond fluorescence decays of thin-film samples, the poor performance of the YD12CN device in the presence of TBP can be understood as being due to the enhanced charge recombination, decreased electron injection, and a lesser extent of inhibition of the intermolecular energy transfer.

Porphyrin sensitizers with π-extended pull units for dye-sensitized solar cells.

New π-extended porphyrin dyes YD26-YD29 with long alkoxyl chains at the ortho positions of the meso-phenyls, and meta di-tert-butylphenyl-substituted porphyrins YD12-CN, and YD13-CN were synthesized for dye-sensitized solar cells, and their optical, electrochemical and photovoltaic properties were investigated and compared with those of YD12 and YD13. The absorption spectra of YD26-YD29 showed a slight red shift of Soret bands and blue shift of Q bands as compared to the meta-substituted porphyrins due to the electron-donating effects of dioctyloxy substituents at the ortho-positions of the meso-phenyl rings. Replacement of the carboxyl with a cyanoacrylic acid as the anchoring group results in significant broadening and red shifts of the absorptions, which is due to the strong electronic coupling between the pull unit and the porphyrin ring facilitated by the C≡C triple bond. The electrochemical studies and quantum-chemical calculations (DFT) indicated that the ortho alkoxy-substituted sensitizers exhibit lower oxidation potential, i.e. a higher HOMO energy level, and their HOMO-LUMO gaps are comparable to the meta-substituted analogues. The photovoltaic measurements confirmed that the ortho-octyloxy groups in the two meso-phenyls of YD26 and YD27 play a significant role in preventing dye aggregation thereby enhancing the corresponding short-circuit current density and open-circuit voltage. The power conversion efficiency (η) of YD26 is 8.04%, which is 11% higher than that of YD12, whereas the efficiency of YD27 is 6.03%, which is 135% higher than that of YD13. On the other hand, the poor performance of YD28 and YD29 is due to the floppy structural nature and limited molecular rigidity of the cyanoacrylic acid anchor.