Several high performance polymer:fullerene bulk-heterojunction photo-active layers, deposited from the non-halogenated solvents o-xylene or anisole in combination with the eco-compatible additive p-anisaldehyde, are investigated. The respective solar cells yield excellent power conversion efficiencies up to 9.5%, outperforming reference devices deposited from the commonly used halogenated chlorobenzene/1,8-diiodooctane solvent/additive combination. The impact of the processing solvent on the bulk-heterojunction properties is exemplified on solar cells comprising benzodithiophenethienothiophene co-polymers and functionalized fullerenes (PTB7:PC71BM). The additive p-anisaldehyde improves film formation, enhances polymer order, reduces fullerene agglomeration and shows high volatility, thereby positively affecting layer deposition, improving charge carrier extraction and reducing drying time, the latter being crucial for future large area roll-to-roll device fabrication.

All‐solution deposited, ITO‐free organic solar cells comprising hybrid top and bottom electrodes and ternary polymer:fullerene photo‐active layers are investigated. A printed micro silver mesh and conductive PEDOT:PSS are employed as bottom electrode on a mechanically flexible PET substrate, whereas the top electrode features highly conductive PEDOT:PSS with dispersed silver nanowires. The highly efficient ternary polymer:fullerene absorber blend PffBT4T‐2OD:PC61BM:PC71BM and all other functional layers are doctor bladed from non‐halogenated solvents in order to comply with the requirements of industrial device fabrication. The semi‐transparent solar cells yield maximum power conversion efficiencies of 6.6% on active areas ≤ 0.1 cm2 and 5.9% on active areas > 1 cm2. Omitting additional bus bars for charge extraction grants the solar cells a homogeneous appearance and transparency perception.

We report on solution‐processed, semitransparent organic solar cells that are implemented as lenses in sunglasses. The electrical power provided by the lens‐fitted solar cells sustains a microelectronic circuit that is used to read out temperature and illumination intensity sensors and to make this information available on two displays integrated into the temples of the “Solar Glasses”. The microelectronic circuit is designed to operate at illumination intensities down to 500 lux, rendering the Solar Glasses suitable for outdoor and indoor use as well as for operation in diffuse light. Hence, this case study provides an example for consumer‐oriented mobile applications, self‐powered by integrated solar cells, which specifically exploit the unique properties of organic solar cells.

A fundamental analysis of the external quantum efficiency (EQE) of organic tandem solar cells with equal absorbers in both subcells (homo‐tandem solar cells) is presented. Providing direct access to both subcells by introducing a conductive intermediate polymer electrode into the recombination zone, without changing the optical and electric device properties, the three‐terminal device becomes a proxy to the two‐terminal tandem solar cell properties. From the spectrally resolved EQE of the subcells in three‐terminal configuration wavelength and intensity of suitable bias light as well as bias voltage are determined that in turn allow for accurate EQE measurements of the common two‐terminal tandem solar cells. Theoretic considerations allow the prediction of the tandem solar cell's EQE from its subcells' EQEs as well as the prediction of the tandem cell EQE under monochromatic bias light illumination being in excellent agreement with experimental results. All findings discussed herein can be applied to more common hetero‐tandem solar cell architectures likewise.

Future low‐cost, high‐throughput production of organic solar cells in roll‐to‐roll printing processes calls for all‐solution‐processable device architectures. Mechanical flexibility and robustness are mandatory to roll the solar foils during printing and to eventually comply with certain end‐user requirements. Here, we report on semitransparent organic solar cells, comprising top and bottom silver nanowire (AgNW) electrodes that were embedded into conductive poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The devices exhibited excellent robustness in bending experiments with radii of 5 and 2.5 mm as well as upon folding. To avoid short circuits from nanowires that could stick out of the bottom electrodes, the PEDOT:PSS:AgNW layers were flattened by hot‐pressing after deposition. All solar cells were fabricated in air by doctor blading and exhibited a clear (haze‐free) transparency due to the absence of bus bars. On photoactive areas of 0.5 cm2, power conversion efficiencies of 3.8 % were obtained.

For future integration into building facades or overhead glazing, the direct deposition of organic solar modules on glass substrates in sheet‐to‐sheet processes may be more cost efficient than postproduction lamination. Complying with the special requirements for the deposition of the layer stack on glass substrates, we report on all‐doctor‐bladed organic solar modules yielding power conversion efficiencies of 4.5 and 3.6 % on photoactive areas of 1 and 20 cm2, respectively. The bottom electrode is doctor bladed from a silver ink atop an adhesion enhancing primer. The top electrode is applied from silver nanowires, dispersed in poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), which thereby avoids any visible bus bars and reduces shading of the active layer. Importantly, all layers are deposited under ambient conditions by using only non‐chlorinated, eco‐compatible solvents.

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Abstract:The effective device photo current of organic tandem solar cells is independent of the angle of light incidence up to 65°. This feature renders these devices particularly suitable for stationary applications where they receive mainly indirect light. In a combined experimental and simulative study, we develop a fundamental understanding of the causal absorption and charge generation mechanisms in organic homo-tandem solar cells. A 3-terminal tandem device architecture is used to measure the optoelectronic properties of both subcells individually. The analysis of the angle dependent external quantum efficiencies of the subcells and the tandem device reveal an internal balancing of the wavelength dependent subcell currents elucidating the low sensitivity of the tandem device properties on the angle of incidence.