@article{ZuoShoaeeKemerinketal.2021,
  author    = {Zuo, Guangzheng and Shoaee, Safa and Kemerink, Martijn and Neher, Dieter},
  title     = {General rules for the impact of energetic disorder and mobility on nongeminate recombination in phase-separated organic solar cells},
  series = {Physical review applied},
  volume    = {16},
  journal   = {Physical review applied},
  number    = {3},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2331-7019},
  doi       = {10.1103/PhysRevApplied.16.034027},
  pages     = {19},
  year      = {2021},
  abstract  = {State-of-the-art organic solar cells exhibit power conversion efficiencies of 18\% and above. These devices benefit from the suppression of free charge recombination with regard to the Langevin limit of charge encounter in a homogeneous medium. It is recognized that the main cause of suppressed free charge recombination is the reformation and resplitting of charge-transfer (CT) states at the interface between donor and acceptor domains. Here, we use kinetic Monte Carlo simulations to understand the interplay between free charge motion and recombination in an energetically disordered phase-separated donor-acceptor blend. We identify conditions for encounter-dominated and resplitting-dominated recombination. In the former regime, recombination is proportional to mobility for all parameters tested and only slightly reduced with respect to the Langevin limit. In contrast, mobility is not the decisive parameter that determines the nongeminate recombination coefficient, k(2), in the latter case, where k2 is a sole function of the morphology, CT and charge-separated (CS) energetics, and CT-state decay properties. Our simulations also show that free charge encounter in the phase-separated disordered blend is determined by the average mobility of all carriers, while CT reformation and resplitting involves mostly states near the transport energy. Therefore, charge encounter is more affected by increased disorder than the resplitting of the CT state. As a consequence, for a given mobility, larger energetic disorder, in combination with a higher hopping rate, is preferred. These findings have implications for the understanding of suppressed recombination in solar cells with nonfullerene acceptors, which are known to exhibit lower energetic disorder than that of fullerenes.},
  language  = {en}
}
@article{ZuWolffRalaiarisoaetal.2019,
  author    = {Zu, Fengshuo and Wolff, Christian Michael and Ralaiarisoa, Maryline and Amsalem, Patrick and Neher, Dieter and Koch, Norbert},
  title     = {Unraveling the Electronic Properties of Lead Halide Perovskites with Surface Photovoltage in Photoemission Studies},
  series = {ACS applied materials \& interfaces},
  volume    = {11},
  journal   = {ACS applied materials \& interfaces},
  number    = {24},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1944-8244},
  doi       = {10.1021/acsami.9b05293},
  pages     = {21578 -- 21583},
  year      = {2019},
  abstract  = {The tremendous success of metal-halide perovskites, especially in the field of photovoltaics, has triggered a substantial number of studies in understanding their optoelectronic properties. However, consensus regarding the electronic properties of these perovskites is lacking due to a huge scatter in the reported key parameters, such as work function (Φ) and valence band maximum (VBM) values. Here, we demonstrate that the surface photovoltage (SPV) is a key phenomenon occurring at the perovskite surfaces that feature a non-negligible density of surface states, which is more the rule than an exception for most materials under study. With ultraviolet photoelectron spectroscopy (UPS) and Kelvin probe, we evidence that even minute UV photon fluxes (500 times lower than that used in typical UPS experiments) are sufficient to induce SPV and shift the perovskite Φ and VBM by several 100 meV compared to dark. By combining UV and visible light, we establish flat band conditions (i.e., compensate the surface-state-induced surface band bending) at the surface of four important perovskites, and find that all are p-type in the bulk, despite a pronounced n-type surface character in the dark. The present findings highlight that SPV effects must be considered in all surface studies to fully understand perovskites' photophysical properties.},
  language  = {en}
}
@article{ZuSchultzWolffetal.2020,
  author    = {Zu, Fengshuo and Schultz, Thorsten and Wolff, Christian Michael and Shin, Dongguen and Frohloff, Lennart and Neher, Dieter and Amsalem, Patrick and Koch, Norbert},
  title     = {Position-locking of volatile reaction products by atmosphere and capping layers slows down photodecomposition of methylammonium lead triiodide perovskite},
  series = {RSC Advances},
  volume    = {10},
  journal   = {RSC Advances},
  number    = {30},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {2046-2069},
  doi       = {10.1039/d0ra03572f},
  pages     = {17534 -- 17542},
  year      = {2020},
  abstract  = {The remarkable progress of metal halide perovskites in photovoltaics has led to the power conversion efficiency approaching 26\%. However, practical applications of perovskite-based solar cells are challenged by the stability issues, of which the most critical one is photo-induced degradation. Bare CH3NH3PbI3 perovskite films are known to decompose rapidly, with methylammonium and iodine as volatile species and residual solid PbI2 and metallic Pb, under vacuum under white light illumination, on the timescale of minutes. We find, in agreement with previous work, that the degradation is non-uniform and proceeds predominantly from the surface, and that illumination under N-2 and ambient air (relative humidity 20\%) does not induce substantial degradation even after several hours. Yet, in all cases the release of iodine from the perovskite surface is directly identified by X-ray photoelectron spectroscopy. This goes in hand with a loss of organic cations and the formation of metallic Pb. When CH3NH3PbI3 films are covered with a few nm thick organic capping layer, either charge selective or non-selective, the rapid photodecomposition process under ultrahigh vacuum is reduced by more than one order of magnitude, and becomes similar in timescale to that under N-2 or air. We conclude that the light-induced decomposition reaction of CH3NH3PbI3, leading to volatile methylammonium and iodine, is largely reversible as long as these products are restrained from leaving the surface. This is readily achieved by ambient atmospheric pressure, as well as a thin organic capping layer even under ultrahigh vacuum. In addition to explaining the impact of gas pressure on the stability of this perovskite, our results indicate that covalently "locking" the position of perovskite components at the surface or an interface should enhance the overall photostability.},
  language  = {en}
}
@article{ZuAmsalemEggeretal.2019,
  author    = {Zu, Fengshuo and Amsalem, Patrick and Egger, David A. and Wang, Rongbin and Wolff, Christian Michael and Fang, Honghua and Loi, Maria Antonietta and Neher, Dieter and Kronik, Leeor and Duhm, Steffen and Koch, Norbert},
  title     = {Constructing the Electronic Structure of CH3NH3PbI3 and CH3NH3PbBr3 Perovskite Thin Films from Single-Crystal Band Structure Measurements},
  series = {The journal of physical chemistry letters},
  volume    = {10},
  journal   = {The journal of physical chemistry letters},
  number    = {3},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1948-7185},
  doi       = {10.1021/acs.jpclett.8b03728},
  pages     = {601 -- 609},
  year      = {2019},
  abstract  = {Photovoltaic cells based on halide perovskites, possessing remarkably high power conversion efficiencies have been reported. To push the development of such devices further, a comprehensive and reliable understanding of their electronic properties is essential but presently not available. To provide a solid foundation for understanding the electronic properties of polycrystalline thin films, we employ single-crystal band structure data from angle-resolved photoemission measurements. For two prototypical perovskites (CH3NH3PbBr3 and CH3NH3PbI3), we reveal the band dispersion in two high-symmetry directions and identify the global valence band maxima. With these benchmark data, we construct "standard" photoemission spectra from polycrystalline thin film samples and resolve challenges discussed in the literature for determining the valence band onset with high reliability. Within the framework laid out here, the consistency of relating the energy level alignment in perovskite-based photovoltaic and optoelectronic devices with their functional parameters is substantially enhanced.},
  language  = {en}
}
@misc{ZimmermannKampeScholzetal.2024,
  author    = {Zimmermann, Matthias and Kampe, Heike and Scholz, Jana and Aust, Sarah-Madeleine and Horn-Conrad, Antje and Engel, Silke and Agrofylax, Luisa and Schlegel, Theresa and Mikulla, Stefanie and Albrecht, Anna Helena and Neher, Dieter and Himmler, Lena},
  title     = {Bildung:digital},
  series = {Portal Wissen: Das Forschungsmagazin der Universit{\"a}t Potsdam},
  journal   = {Portal Wissen: Das Forschungsmagazin der Universit{\"a}t Potsdam},
  number    = {01/2024},
  issn      = {2194-4245},
  doi       = {10.25932/publishup-63129},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-631291},
  pages     = {98},
  year      = {2024},
  abstract  = {Heute Morgen schon im Bett geswiped, geliked oder gepostet? Auf Arbeit an einer Video-Konferenz teilgenommen, eine Datenbank benutzt oder programmiert? Auf dem Heimweg schnell noch im Laden mit dem Smartphone bezahlt, Podcasts geh{\"o}rt und die Ausleihe der Bibliotheksb{\"u}cher verl{\"a}ngert? Und abends auf der Couch mit dem Tablet auf ELSTER.de die Steuererkl{\"a}rung ausgef{\"u}llt, online geshoppt oder Rechnungen bezahlt, ehe die Streaming-Plattform mit einer Serie lockt? Unser Leben ist durch und durch digitalisiert. Diese Ver{\"a}nderungen machen vieles schneller, leichter, effizienter. Doch damit Schritt zu halten, verlangt uns einiges ab und gelingt beileibe nicht allen. Es gibt Menschen, die f{\"u}r eine {\"U}berweisung lieber zur Bank gehen, das Programmieren den Experten {\"u}berlassen, die Steuererkl{\"a}rung per Post schicken und das Smartphone nur zum Telefonieren benutzen. Sie wollen nicht, vielleicht k{\"o}nnen sie auch nicht. Haben es nicht gelernt. Andere, j{\"u}ngere Menschen, wachsen als „Digital Natives" inmitten digitaler Ger{\"a}te, Tools und Prozesse auf. Aber k{\"o}nnen sie deshalb wirklich damit umgehen? Oder brauchen auch sie digitale Bildung? Aber wie sieht erfolgreiche digitale Bildung eigentlich aus? Lernen wir dabei ein Tablet zu bedienen, richtig zu googeln und Excel-Tabellen zu schreiben? M{\"o}glicherweise geht es um mehr: darum, den umfassenden Wandel zu verstehen, der unsere Welt erfasst, seitdem sie in Einsen und Nullen zerlegt und virtuell neu aufgebaut wird. Aber wie lernen wir, in einer Welt der Digitalit{\"a}t zu leben - mit allem, was dazu geh{\"o}rt und zu unserem Nutzen? F{\"u}r die aktuelle Ausgabe der „Portal Wissen" haben wir uns an der Universit{\"a}t Potsdam umgeschaut, welche Rolle die Verbindung von Digitalisierung und Lernen in der Forschung der verschiedenen Disziplinen spielt: Wir haben mit Katharina Scheiter, Professorin f{\"u}r digitale Bildung, {\"u}ber die Zukunft in deutschen Schulen gesprochen und uns gleich von mehreren Expert*innen Beispiele daf{\"u}r zeigen lassen, wie digitale Instrumente schulisches Lernen, aber auch Weiterbildung im Berufsleben verbessern k{\"o}nnen. Außerdem haben uns Forschende aus Informatik und Agrarforschung vorgef{\"u}hrt, wie auch gestandene Landwirte dank digitaler Hilfsmittel noch viel {\"u}ber ihr Land und ihre Arbeit lernen k{\"o}nnen. Wir haben mit Bildungsforschenden gesprochen, die mithilfe von Big Data analysieren, wie Jungen und M{\"a}dchen lernen und wo m{\"o}gliche Ursachen f{\"u}r Unterschiede zu suchen sind. Die Bildungsund Politikwissenschaftlerin Nina Kolleck wiederum schaut auf Bildung vor dem Hintergrund der Globalisierung und setzt dabei auf die Auswertung von großen Mengen Social-Media- Daten. Dabei verlieren wir nat{\"u}rlich die Vielfalt der Forschung an der Uni Potsdam nicht aus den Augen: Wir stellen der Strafrechtlerin Anna Albrecht 33 Fragen, begleiten eine Gruppe von Geoforschenden in den Himalaya und lassen uns erkl{\"a}ren, welche Alternativen es bald zu Antibiotika geben k{\"o}nnte. Außerdem geht es in diesem Magazin um Stress und wie er uns krankmacht, die Forschung zu nachhaltiger Erzgewinnung und neue Ans{\"a}tze in der Schulentwicklung. Neu ist auch eine ganze Reihe k{\"u}rzerer Beitr{\"a}ge, die zum Bl{\"a}ttern und Schm{\"o}kern einladen: von Forschungsnews und Personalia- Infos {\"u}ber fotografische Einblicke in Labore, einfache Erkl{\"a}rungen komplexer Ph{\"a}nomene und Ausblicke in die weite Forschungswelt bis hin zu einer kleinen Wissenschaftsutopie, einem pers{\"o}nlichen Dank an die Forschung und einem Wissenschaftscomic. All das im Namen der Bildung, versteht sich. Viel Vergn{\"u}gen bei der Lekt{\"u}re!},
  language  = {de}
}
@article{ZhangStolterfohtArminetal.2018,
  author    = {Zhang, Shanshan and Stolterfoht, Martin and Armin, Ardalan and Lin, Qianqian and Zu, Fengshuo and Sobus, Jan and Jin, Hui and Koch, Norbert and Meredith, Paul and Burn, Paul L. and Neher, Dieter},
  title     = {Interface Engineering of Solution-Processed Hybrid Organohalide Perovskite Solar Cells},
  series = {ACS applied materials \& interfaces},
  volume    = {10},
  journal   = {ACS applied materials \& interfaces},
  number    = {25},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1944-8244},
  doi       = {10.1021/acsami.8b02503},
  pages     = {21681 -- 21687},
  year      = {2018},
  abstract  = {Engineering the interface between the perovskite absorber and the charge-transporting layers has become an important method for improving the charge extraction and open-circuit voltage (V-OC) of hybrid perovskite solar cells. Conjugated polymers are particularly suited to form the hole-transporting layer, but their hydrophobicity renders it difficult to solution-process the perovskite absorber on top. Herein, oxygen plasma treatment is introduced as a simple means to change the surface energy and work function of hydrophobic polymer interlayers for use as p-contacts in perovskite solar cells. We find that upon oxygen plasma treatment, the hydrophobic surfaces of different prototypical p-type polymers became sufficiently hydrophilic to enable subsequent perovskite junction processing. In addition, the oxygen plasma treatment also increased the ionization potential of the polymer such that it became closer to the valance band energy of the perovskite. It was also found that the oxygen plasma treatment could increase the electrical conductivity of the p-type polymers, facilitating more efficient charge extraction. On the basis of this concept, inverted MAPbI(3) perovskite devices with different oxygen plasma-treated polymers such as P3HT, P3OT, polyTPD, or PTAA were fabricated with power conversion efficiencies of up to 19\%.},
  language  = {en}
}
@article{ZhangHosseiniGunderetal.2019,
  author    = {Zhang, Shanshan and Hosseini, Seyed Mehrdad and Gunder, Rene and Petsiuk, Andrei and Caprioglio, Pietro and Wolff, Christian Michael and Shoaee, Safa and Meredith, Paul and Schorr, Susan and Unold, Thomas and Burn, Paul L. and Neher, Dieter and Stolterfoht, Martin},
  title     = {The Role of Bulk and Interface Recombination in High-Efficiency Low-Dimensional Perovskite Solar Cells},
  series = {Advanced materials},
  volume    = {31},
  journal   = {Advanced materials},
  number    = {30},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0935-9648},
  doi       = {10.1002/adma.201901090},
  pages     = {11},
  year      = {2019},
  abstract  = {2D Ruddlesden-Popper perovskite (RPP) solar cells have excellent environmental stability. However, the power conversion efficiency (PCE) of RPP cells remains inferior to 3D perovskite-based cells. Herein, 2D (CH3(CH2)(3)NH3)(2)(CH3NH3)(n-1)PbnI3n+1 perovskite cells with different numbers of [PbI6](4-) sheets (n = 2-4) are analyzed. Photoluminescence quantum yield (PLQY) measurements show that nonradiative open-circuit voltage (V-OC) losses outweigh radiative losses in materials with n > 2. The n = 3 and n = 4 films exhibit a higher PLQY than the standard 3D methylammonium lead iodide perovskite although this is accompanied by increased interfacial recombination at the top perovskite/C-60 interface. This tradeoff results in a similar PLQY in all devices, including the n = 2 system where the perovskite bulk dominates the recombination properties of the cell. In most cases the quasi-Fermi level splitting matches the device V-OC within 20 meV, which indicates minimal recombination losses at the metal contacts. The results show that poor charge transport rather than exciton dissociation is the primary reason for the reduction in fill factor of the RPP devices. Optimized n = 4 RPP solar cells had PCEs of 13\% with significant potential for further improvements.},
  language  = {en}
}
@article{ZersonNeumannSteyrleuthneretal.2016,
  author    = {Zerson, Mario and Neumann, Martin and Steyrleuthner, Robert and Neher, Dieter and Magerle, Robert},
  title     = {Surface Structure of Semicrystalline Naphthalene Diimide-Bithiophene Copolymer Films Studied with Atomic Force Microscopy},
  series = {Macromolecules : a publication of the American Chemical Society},
  volume    = {49},
  journal   = {Macromolecules : a publication of the American Chemical Society},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0024-9297},
  doi       = {10.1021/acs.macromol.6b00988},
  pages     = {6549 -- 6557},
  year      = {2016},
  language  = {en}
}
@article{ZentelBehlNeheretal.2004,
  author    = {Zentel, Rudolf and Behl, Marc and Neher, Dieter and Zen, Achmad and Lucht, Sylvia},
  title     = {Nanostructured polytriarylamines : orientation layers for polyfluorene},
  issn      = {0065-7727},
  year      = {2004},
  language  = {en}
}
@article{ZenSaphiannikovaNeheretal.2006,
  author    = {Zen, Achmad and Saphiannikova, Marina and Neher, Dieter and Grenzer, J{\"o}rg and Grigorian, Souren A. and Pietsch, Ullrich and Asawapirom, Udom and Janietz, Silvia and Scherf, Ullrich and Lieberwirth, Ingo and Wegner, Gerhard},
  title     = {Effect of molecular weight on the structure and crystallinity of poly(3-hexylthiophene)},
  doi       = {10.1021/Ma0521349},
  year      = {2006},
  abstract  = {Recently, two different groups have reported independently that the mobility of field-effect transistors made from regioregular poly(3-hexylthiophene) (P3HT) increases strongly with molecular weight. Two different models were presented: one proposing carrier trapping at grain boundaries and the second putting emphasis on the conformation and packing of the polymer chains in the thin layers for different molecular weights. Here, we present the results of detailed investigations of powders and thin films of deuterated P3HT fractions with different molecular weight. For powder samples, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were used to investigate the structure and crystallization behavior of the polymers. The GPC investigations show that all weight fractions possess a rather broad molecular weight distribution. DSC measurements reveal a strong decrease of the crystallization temperature and, most important, a significant decrease of the degree of crystallinity with decreasing molecular weight. To study the structure of thin layers in lateral and vertical directions, both transmission electron microscopy (TEM) and X-ray grazing incidence diffraction (GID) were utilized. These methods show that thin layers of the low molecular weight fraction consist of well-defined crystalline domains embedded in a disordered matrix. We propose that the transport properties of layers prepared from fractions of poly(3-hexylthiophene) with different molecular weight are largely determined by the crystallinity of the samples and not by the perfection of the packing of the chains in the individual crystallites},
  language  = {en}
}