Photovoltaic limitations of BODIPY:fullerene based bulk heterojunction solar cells

- BODYPI/Fullerene based OPVs show high photo-voltage and in some cases high absorption coefficient.
- Un-optimized morphology, carrier collection property and low carrier mobility affect short circuit current (Jsc) and Fill Factor (FF) values.
- Fractionation process to eliminate low molecular weight species (impurities) can be used to improve short circuit current.
- Suitable choice of electrodes to reduce energetic barriers for hole carrier collection is shown to improve FF.

The photovoltaic performance of blends of a series of 4,4′-Difluoro-4-bora-3a,4a-diaza-s-indacenes)-based (BODIPY) conjugated polymers donors with fullerene electron acceptors is investigated. Despite the high Voc values observed, solar cell device yields relatively low power conversion efficiencies. Our study takes into account the materials' structure-property relationship, light harvesting capabilities, charge transport, collection properties and morphological characteristics to elucidate factors affecting the photovoltaic performance in this class of polymers. We show that elimination of low molecular weight species and suitable electrodes for hole collection can be used to overcome some of the observed limitations on photovoltaic performance.

The photovoltaic performance of blends of a series of 4,4′-Difluoro-4-bora-3a,4a-diaza-s-indacenes)-based (BODIPY) conjugated polymers donors with fullerene electron acceptors is thoroughly investigated aiming to elucidate on the factors that, at present, prevent high power conversion efficiencies values. We have shown that a fractionation process and suitable choice of electrodes can be used to overcome some of the photovoltaic performance limitations.108