Intercalated vs Nonintercalated Morphologies in Donor-Acceptor Bulk Heterojunction Solar Cells: PBTTT:Fullerene Charge Generation and Recombination Revisited

Regioisomeric thieno[3,4-d]thiazole-based A-Q-D-Q-A-type NIR acceptors for efficient non-fullerene organic solar cells

This study explores the potential of regioisomeric quinoidal-resonance π-spacers in designing near-infrared (NIR) non-fullerene acceptors (NFAs) for high-performance organic solar cell devices. Adopting thienothiazole as the π-spacer, two new isomeric A-Q-D-Q-A NFAs, TzN-S and TzS-S, are designed and synthesized. Both NFAs demonstrate a broad spectral response extended to the NIR region. However, they exhibit different photovoltaic properties when they were mixed with the PCE10 donor to fabricate respective solar cells. The optimal device of TzS-S achieves a PCE of 10.75%, much higher than that of TzN-S based ones (6.13%). The more favorable energetic offset and better molecular packing contribute to the better charge generation and transport, which explains the relative superiority of TzS-S NFA. This work sheds new light on the regioisomeric effect of component materials for optoelectronic applications.

Observing the On-Site Generation of Excitons and Charges by Low-Temperature Spectroscopy

Understanding the relation between phase morphology and physical processes in polymer blends is the key to the fabrication of reproducible and reliable polymer optoelectronic devices. In this work, taking the advantage of low-temperature spectroscopy, we have observed the on-site generation of excitons and long-lived charges in different phase morphology polymer/fullerene blends. Probing at 10K, the photo-generated species are localized to where they are generated. We found that the generation of excitons and long-lived charges is highly influenced by the local molecular phase morphology. We further demonstrated that although the influence of phase morphology is localized to the place that excitons and long-lived charges are generated, this influence can persist over sub-millisecond timescales. Thus, we believe that the fate of excitons and long-lived charges is determined by the location at which they are generated, which can in turn be controlled precisely by molecular phase morphology.

Systematic review elucidating the generations and classifications of solar cells contributing towards environmental sustainability integration

Rapid escalation in energy demand and pressure over finite fossil fuels reserves with augmenting urbanization and industrialization points towards adoption of cleaner, sustainable and eco-friendly sources to be employed. Solar cell devices known for efficient conversion of solar energy to electrical energy have been attracting scientific community due to their remarkable conformity with the principles of green chemistry. The future candidacy of solar cells is expressed by their efficient conversion. Such a great potential associated with solar cells has instigated research since many decades leading to the emergence of a wide myriad of solar cells devices with novel constituent materials, designs and architecture reflected in form of three generations of the solar cells. Considering the cleaner and sustainability aspects of the solar energy, current review has systematically compiled different generations of solar cells signifying the advancements in terms of architecture and compositional parameters. In addition to the chronological progression of solar cells, current review has also focused on the innovations done in improvement of solar cells. In terms of efficiency and stability, photovoltaic community is eager to achieve augmented efficiencies and stabilities for using solar cells as an alternative to the conventional fossil fuels.

Increases in the Charge Separation Barrier in Organic Solar Cells Due to Delocalization

Because of the low dielectric constant, charges in organic solar cells must overcome a strong Coulomb attraction in order to separate. It has been widely argued that intermolecular delocalization would assist charge separation by increasing the effective initial electron-hole separation in a charge-transfer state, thus decreasing their barrier to separation. Here we show that this is not the case: including more than a small amount of delocalization in models of organic solar cells leads to an increase in the free-energy barrier to charge separation. Therefore, if delocalization were to improve the charge separation efficiency, it would have to do so through nonequilibrium kinetic effects that are not captured by a thermodynamic treatment of the barrier height.