The widespread use of solar cells as a renewable source of energy is seriously held back by the high cost of the existing crystalline silicon-based technology. The prospect of cheap reel-to-reel processing makes organic semiconducting mate-

Organic photodetectors (OPDs) have gained increasing interest as they offer cost-effective fabrication methods using low temperature processes, making them particularly attractive for large area image detectors on lightweight flexible plastic substrates. Moreover, their photophysical and optoelectronic properties can be tuned both at a material and device level. Visible-light OPDs are proposed for use in indirect-conversion X-ray detectors, fingerprint scanners, and intelligent surfaces for gesture recognition. Near-infrared OPDs find applications in biomedical imaging and optical communications. For most applications, minimizing the OPD dark current density (J d ) is crucial to improve important figures of merits such as the signal-to-noise ratio, the linear dynamic range, and the specific detectivity (D*). Here, a quantitative analysis of the intrinsic dark current processes shows that charge injection from the electrodes is the dominant contribution to J d in OPDs. J d reduction is typically addressed by fine-tuning the active layer energetics and stratification or by using charge blocking layers. Yet, most experimental J d values are higher than the calculated intrinsic limit. Possible reasons for this deviation are discussed, including extrinsic defects in the photoactive layer and the presence of trap states. This provides the reader with guidelines to improve the OPD performances in view of imaging applications.

The morphology of composite thin films consisting of a conjugated polymer (poly[2-methoxy-5-(3‘,7‘-dimethyloctyloxy)-1,4-phenylenevinylene], MDMO-PPV) and methanofullerene ([6,6]-phenyl C61 butyric acid methyl ester, PCBM), which are used as the active layer in polymer photovoltaic devices, has been extensively studied using transmission electron microscopy (TEM) and selected-area electron diffraction (SAED). Composite MDMO-PPV:PCBM films have been prepared with PCBM concentrations varying from 20 to 90 wt %. PCBM-rich clusters are clearly observed in TEM bright-field mode when the PCBM concentration is increased to ca. 75 wt % in the composite film. The SAED analysis shows that these clusters consist of many PCBM nanocrystals with random crystallographic orientations. Furthermore, we show that these nanocrystals are also present in the homogeneous matrix at PCBM concentrations below 75 wt %. Annealing of the blend films has been performed at temperatures between 60 and 130 °C for different times. In all cases, but especially when the annealing temperature is above the glass transition temperature of MDMO-PPV (∼80 °C), PCBM molecules show high diffusion mobility, resulting in accelerated phase segregation and in the formation of large PCBM single crystals in the film. The observed phase segregation, even at temperatures as low as 60 °C, indicates that the thermal stability of MDMO-PPV:PCBM films will likely limit the long-term performance of solar cells based on these materials.

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We present studies of steady-state photoinduced absorption (PIA) spectroscopy on photoexcitations in a series of well-defined a-oligothiophene (T,, , n=6, 7, 9, and 11) films and solutions. The PIA spectra and the excited state lifetimes are consistent with the signatures of a photoexcited triplet state. The PIA spectra consist of a strong vibronically resolved subgap absorption, which is readily observed in solid-state films and in solutions at ambient and cryogenic temperatures. The transition energy is linearly dependent on the reciprocal chain length and shifts to lower energy for longer oligomers. Variation of the modulation frequency and the pump intensity under matrix-isolated conditions reveals that the photoexcitation is created via an intrachain mechanism and decays nonradiatively with monomolecular kinetics. In solid films we find a significant contribution of a bimolecular decay process to the relaxation rate.

Following the 2nd release of the "Emerging PV reports," the best achievements in the performance of emerging photovoltaic devices in diverse emerging photovoltaic research subjects are summarized, as reported in peer-reviewed articles in academic journals since August 2021. Updated graphs, tables, and analyses are provided with several performance parameters, e.g., power conversion efficiency, open-circuit voltage, short-circuit current density, fill factor, light utilization efficiency, and stability test energy yield. These parameters are presented as a function of the photovoltaic bandgap energy and the average visible transmittance for each technology and application, and are put into perspective using, e.g., the detailed balance efficiency limit. The 3rd installment of the "Emerging PV reports" extends the scope toward triple junction solar cells.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/aenm.202203313.

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Strong multiple complexation of transition metal ions, Cu(II), Zn(I1) and Ni(I1) with different generations of well-defined poly(propy1ene imine) dendrimers as multi(tridentate) li-metal ions from 2 up to 32.gands has been used to construct nanoscopic assemblies of defined structure and size incorporating a distinct number of Metal-containing architectures of nanoscopic dimensions are thought to create new materials with promising electronic, magnetic or catalytic properties [']. Polyniers with metal-coordinating side g r o~p s [~%~] or amphiphilic assembliesr41 are most commonly used in this field. However, their three-dimensional architectures are less defined, due to the polydispersity of polymers and the dynamic character of amphiphilic assemblies. Recently, well-defined structures of dendritic macromolecules, like 1 (Scheme l), have become available. These macromolecules emanate from a central core with a branching point at each monomer unit and possesb a defined number of generations and end groups [5]. Therefore, dendrimers are well suited for nanoscopic materials, e.g. in the complexation of metals. Organometallic complexes have been used in the construction of assembly points of dendritic branched6 91 and in end-group functionalization of dendrimers['"-"1. I 2It has been reported that the bis(3-aminopropy1)aminc functionality acts as a strongly complexing tridentate coordinating site for various transition metals (2)['3-'01. Cu(I1j complexes with his( 3-aminopropy1)amine are formed with high equilibrium constants of K = loi4 M-1[i71. Furthermore detailed insight into many complexes is obtained from single crystal X-ray data. Here we demonstrate that, with different generations of poly(propy1ene imine) dendrimers [DAB-dendr-(NH,),,; n 4, 8, 16, 32, 641 as multifunctional ligands, it is possible to prepare metal-containing nanoscopic structures incorporating a well-defined number of up to 32 transition metal ions such as Cu(llj, Zn(lI), and Ni(I1). Essential to this result is the combination of the high degree of definition attainable for poly(propy1ene imine) dendrimers and the metal-coordinating properties of the bis(3-aminopropy1)aniine end groups.Poly(propy1ene imme) dendrimers are synthesized in a stepwise manner from a central core, leading to a doubling of the end groups in every next generation up to 64 for the fifth generation (1) [18]. A high degree of definition of these structures has been established with electrospray mass spectroscopy, revealing a monodispersity of 1.0018 for the highest generation (1, n = 64)[191. The addition of metal(I1)chloride (MC12, with M = Cu, Zn, and Ni) in methanol to methanolic solutions of the dendrimers of different generations yielded the exclusive formation of the dendritic polybis(3-arninopropy1)amine-MCl2 complexes. We have studied both the formation and the structure of these metallodendrimers with a number of different techniques.Addition of CuC12 to different of generations poly(propylene imine) dendrimers in methanol resuIts in the immediate formation of...