Limiting factors for charge generation in low-offset fullerene-based organic solar cells.

Free charge generation after photoexcitation of donor or acceptor molecules in organic solar cells generally proceeds via (1) formation of charge transfer states and (2) their dissociation into charge separated states. Research often either focuses on the first component or the combined effect of both processes. Here, we provide evidence that charge transfer state dissociation rather than formation presents a major bottleneck for free charge generation in fullerene-based blends with low energetic offsets between singlet and charge transfer states.

Multifunctional ytterbium oxide buffer for perovskite solar cells.

Perovskite solar cells (PSCs) comprise a solid perovskite absorber sandwiched between several layers of different charge-selective materials, ensuring unidirectional current flow and high voltage output of the devices. A 'buffer material' between the electron-selective layer and the metal electrode in p-type/intrinsic/n-type (p-i-n) PSCs (also known as inverted PSCs) enables electrons to flow from the electron-selective layer to the electrode. Furthermore, it acts as a barrier inhibiting the inter-diffusion of harmful species into or degradation products out of the perovskite absorber.

Vacuum-Deposited Donors for Low-Voltage-Loss Nonfullerene Organic Solar Cells.

The advent of nonfullerene acceptors (NFAs) enabled records of organic photovoltaics (OPVs) exceeding 19% power conversion efficiency in the laboratory. However, high-efficiency NFAs have so far only been realized in solution-processed blends. Due to its proven track record in upscaled industrial production, vacuum thermal evaporation (VTE) is of prime interest for real-world OPV commercialization.

Assessing the Photovoltaic Quality of Vacuum-Thermal Evaporated Organic Semiconductor Blends.

Vacuum-thermal evaporation (VTE) is a highly relevant fabrication route for organic solar cells (OSCs), especially on an industrial scale as proven by the commercialization of organic light emitting diode-based displays. While OSC performance is reported for a range of VTE-deposited molecules, a comprehensive assessment of donor:acceptor blend properties with respect to their photovoltaic performance is scarce. Here, the organic thin films and solar cells of three select systems are fabricated and ellipsometry, external quantum efficiency with high dynamic range, as well as OTRACE are measured to quantify absorption, voltage losses, and charge carrier mobility.

Controlling energy levels and Fermi level en route to fully tailored energetics in organic semiconductors.

Simultaneous control over both the energy levels and Fermi level, a key breakthrough for inorganic electronics, has yet to be shown for organic semiconductors. Here, energy level tuning and molecular doping are combined to demonstrate controlled shifts in ionisation potential and Fermi level of an organic thin film. This is achieved by p-doping a blend of two host molecules, zinc phthalocyanine and its eight-times fluorinated derivative, with tunable energy levels based on mixing ratio.