Researchers from Nanyang Technological University, Singapore, have developed a novel biomass-derived polymer for hybrid organic-inorganic perovskite solar cells (HPSC). It reportedly improved both efficiency and stability compared to reference devices.

The PBDF-DFC material is also claimed to enable potentially simpler fabrication processes.

“The research was inspired by two key challenges in current perovskite solar cells: environmental concerns about petroleum-derived polymers currently used as photoactive layers, and complex fabrication processes due to polymer solubility limitations of existing conjugated polymers,” corresponding author, Leonard Ng Wei Tat, told pv magazine.

The scientists sought an alternative to conjugated polymers based on petroleum-based thiophene, which require precursor solvents and are reportedly more complicated to fabricate.

Furan is extracted from agricultural waste and contains chalcogen aromatic compounds, noted the team. The PBDF-DFC polymers based on it are highly soluble in perovskite precursor solvents, enabling a simplified direct precursor integration fabrication method.

“The PBDF-DFC exhibits high solubility compared to incumbent precursor solvents, allowing direct incorporation into the precursor solution,” said the researchers. This “significantly” streamlines the fabrication process, reducing steps and potentially lowering production costs.

“The biggest challenge was working with furan-based polymers, which had been underexplored in perovskite solar cells despite their potential benefits,” said Ng Wei Tat, explaining that the team had to develop new furan synthesis approaches to overcome lower yields of 15% versus 70% compared to traditional thiophene-based synthesis. “We also had to explore new ways of integrating the furan-based polymers directly into the device stack.”

To test their new material, the researchers examined a hexane-soluble fraction that they labeled FP1-H and a chloroform-soluble fraction, labeled FP1-C. The FP1-H was used by the team in an HPSC based on a stack as follows: indium tin oxide (ITO) glass, tin(IV) oxide (SnO2) electron transport layer (ETL), perovskite-FP1-H, Spiro-OMeTAD layer and silver (Au) electrode contacts.

The experiment’s control device had a maximum efficiency of 19.84% with a short circuit current density of 22.81 mA cm-2, an open circuit voltage of 1.10 V, and a fill factor of 75.88%. The champion HPSC had a maximum efficiency of 21.39% with a short-circuit current density of 24.17 mA cm-2, an open circuit voltage of 1.08 V, and a fill factor of 76.60%.

Using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy to analyze samples, the team noted that “the PBDF-DFC accumulates at grain boundaries, improving film crystallization and reducing defects.” It stressed that the “dual innovation of a new polymer and simplified fabrication process” offers a chance to make HPSCs more efficient, stable, and potentially more sustainable.

“The successful integration of PBDF-DFC and the direct precursor integration method opens new avenues for streamlined production of high-performance perovskite solar cells, addressing key challenges in scalability and environmental impact,” the academics concluded.

Their work is described in “Direct Integration of Biomass-Derived Furan Polymers for Enhanced Stability and Efficiency in Hybrid Perovskite Solar Cells,” published in Advanced Functional Materials.

With an eye on the potential for HPSC performance enhancement, Ng said, “Future work will focus on optimizing device stability through innovative modifications to the device architecture, while exploring scalable manufacturing processes.”

It involves work on novel device stack configurations, interface engineering approaches, and alternative electron and hole transport layers.

“A key priority is adapting their direct precursor integration method for industrial-scale production, particularly exploring printable photovoltaic systems using inkjet, screen, and roll-to-roll printing techniques,” said Ng Wei Tat, adding that real-world testing in a variety of environmental conditions is also planned.

Other biomass-derived materials could further enhance performance and sustainability, according to Ng Wei Tat. “The solution-processability of the furan-based polymer also opens possibilities for developing flexible and lightweight perovskite solar cells, potentially enabling new device architectures that weren't feasible with traditional petroleum-based polymers,” he concluded.

by pv magazine