The efficiency of thin-film solar cells with large optical band gaps, such as organic bulk heterojunction or amorphous silicon solar cells, is limited by their inability to harvest the (infra)red part of the solar spectrum. Photochemical upconversion based on triplet–triplet annihilation (TTA-UC) can potentially boost those solar cells by absorbing sub-bandgap photons and coupling the upconverted light back into the solar cell in a spectral region that the cell can efficiently convert into electrical current. In the present study we augment two types of organic solar cells and one amorphous silicon (a-Si:H) solar cell with a TTA-upconverter, demonstrating a solar cell photocurrent increase of up to 0.2% under a moderate concentration (19 suns). The behavior of the organic solar cells, whose augmentation with an upconverting device is so-far unreported, is discussed in comparison to a-Si:H solar cells. Furthermore, on the basis of the TTA rate equations and optical simulations, we assess the potential of TTA-UC augmented solar cells and highlight a strategy for the realization of a device-relevant current increase by TTA-upconversion.

In this work, we report on indium tin oxide-free, all-solution processed transparent organic light emitting diodes (OLEDs) with inverted device architecture. Conductive polymer layers are employed as both transparent cathodes and transparent anodes, with the top anodes having enhanced conductivities from a supporting stochastic silver nanowire mesh. Both electrodes exhibit transmittances of 80-90% in the visible spectral regime. Upon the incorporation of either yellow- or blue-light emitting fluorescent polymers, the OLEDs show low onset voltages, demonstrating excellent charge carrier injection from the polymer electrodes into the emission layers. Overall luminances and current efficiencies equal the performance of opaque reference OLEDs with indium tin oxide and aluminium electrodes, proving excellent charge carrier-to-light conversion within the device.

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.

Window‐ or building‐integrated semi‐transparent solar cells are particularly interesting applications for organic photovoltaic devices. In this work, we present an easy‐to‐process inverted device architecture comprising fully solution processable poly(3,4‐ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) bilayer top‐electrodes for efficient semi‐transparent organic solar cells. By incorporating dyes with a complementary absorption to the light harvesting polymer poly[[9‐(1‐octylnonyl)‐9H‐carbazole‐2,7‐diyl]‐2,5‐thiophenediyl‐2,1,3‐benzothiadiazole‐4,7‐diyl‐2,5‐thiophenediyl] (PCDTBT) into the PEDOT:PSS electrode, we achieve fully color neutral transparency perception and a color rendering index approaching 100. This makes the devices suitable for applications such as window shadowing or the integration into overhead glazing.