Organic photodetectors with inverted structure are fabricated by solution process techniques. A very thin interfacing layer of polyethyleneimine leads to a homogenous interface with low work function. The devices exhibit excellent performances, in particular in terms of low dark current density, wide range linearity, high detectivity, and remarkable stability in ambient air without encapsulation.

Geminate recombination of bound polaron pairs at the donor/acceptor interface is one of the major loss mechanisms in organic bulk heterojunction solar cells. One way to overcome Coulomb attraction between opposite charge carriers and to achieve their full dissociation is the introduction of high dielectric permittivity materials such as nanoparticles of narrow band gap semiconductors. We selected CuInS2 nanocrystals of 7.4 nm size, which present intermediate energy levels with respect to poly(3-hexylthiophene) (P3HT) and Phenyl-C61-butyric acid methyl ester (PCBM). Efficient charge transfer from P3HT to nanocrystals takes place as evidenced by light-induced electron spin resonance. Charge transfer between nanocrystals and PCBM only occurs after replacing bulky dodecanethiol (DDT) surface ligands with shorter 1,2-ethylhexanethiol (EHT) ligands. Solar cells containing in the active layer a ternary blend of P3HT:PCBM:CuInS2-EHT nanocrystals in 1:1:0.5 mass ratio show strongly improved short circuit current density and a higher fill factor with respect to the P3HT:PCBM reference device. Complementary measurements of the absorption properties, external quantum efficiency and charge carrier mobility indicate that enhanced charge separation in the ternary blend is at the origin of the observed behavior. The same trend is observed for blends using the glassy polymer poly(triarylamine) (PTAA).

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This work is a re-investigation of the impact of blend morphology and thermal annealing on

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The External Quantum Efficiency (EQE) of semi-transparent Bulk Hetero-Junction (BHJ) organic photodiodes processed in air shows significant differences when measured from the front or back side contacts. This difference was found significantly reduced when decreasing the active layer thickness or by applying a negative bias. This work brings new elements to help understanding this effect, providing a large set of experiments featuring different applied voltages, active layers, process conditions and electron and hole layers. By the mean of detailed electrical simulations, all these measurements have been found consistent with the mechanisms of irreversible photooxidation, modeled as deep trap states (and not as p type doping). The EQE measurement from front and back side is thus a simple and efficient way of monitoring the presence and amplitude of oxygen contamination in BHJ organic solar cells and photodiodes.

Progress in the modeling of charge transport in solution processed solar cells and photodiodes is reviewed. Through several examples involving modeling and original experiments, the role of intentional doping, structural defects, and oxygen contamination are discussed.

Fingerprint on Display (FoD) Modules based on organic photodetectors have been realized and have achieved high performances for integration within smartphones. Such modules allow full display size enabling multiple fingers authentication at once and increasing security level.