Structure modification of isoindigo copolymer synthesized by direct arylation that improves the open circuit voltage on organic solar cells

Design and synthesis of two photovoltaic materials as electro-donors based on isoindigo (PFI) or diketopyrrolopyrrol (PFDPPT-A) and fluorene connected by thiophenes was carried out to obtain -(D- n-A) n polymers. These photovoltaic materials were synthetized by using the direct arylation (DA) reaction as a polymerization process promoting the use of low-cost methodology. Molecular structure of copolymers was stablished by IR, H 1 -NMR experiments as well as determination of molecular weight. The electronic architecture of PFI and PFDPPT-A were estimated by theoretical study and confirmed by absorption spectroscopy and electrochemical measurements, corroborating the intramolecular charge transfer from donor to acceptor fragments. A comparison of energy levels and optical features of polymers that contain similar structure was developed to evaluate the effect of n-bridge elongation in photovoltaic responses. Photovoltaic performance of the PFI and PFDPPT-A were evaluated into the active layer of organic solar cells (OSCs) within the BHJ approach; devices were fabricated under regular atmosphere conditions including the top electrode. Voc produced for PFI -based OSCs shows a high values (1.05 V) compared with previous isoindigo derivatives reports, showing the improvement of photovoltaic character by addition of thiophene ring

Automated summary

Two photovoltaic materials based on isoindigo (PFI) or diketopyrrolopyrrol (PFDPPT-A) and fluorene connected by thiophenes were designed and synthesized as electro-donors to obtain -(D-π-A) n polymers. Low-cost methodology was promoted by using the direct arylation (DA) reaction as a polymerization process for the synthesis of these photovoltaic materials. The molecular structure of the copolymers was established by IR, H 1 -NMR experiments, and determination of molecular weight. The electronic architecture of PFI and PFDPPT-A was estimated by theoretical study and confirmed by absorption spectroscopy and electrochemical measurements, confirming the intramolecular charge transfer. Evaluating the effect of n-bridge elongation on photovoltaic responses, a comparison of energy levels and optical features of polymers with similar structures was developed. The photovoltaic performance of PFI and PFDPPT-A was evaluated in organic solar cells (OSCs) using the BHJ approach and devices were fabricated under regular atmosphere conditions, showing improved photovoltaic character with the addition of thiophene ring, with PFI-based OSCs displaying a high Voc value of 1.05 V compared to previous isoindigo derivatives reports.