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Mazza, Samuel M.

Publications and source records attributed to Mazza, Samuel M..

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Nanoribbons or weakly connected acenes? The influence of pyrene insertion on linearly extended ring systems

Derived from the lateral fusion of benzene rings, acenes are a class of π-conjugated molecules containing a single aromatic sextet, where system size is inversely correlated with chemical stability. In the pursuit of creating graphene nanoribbons/nanowires, several extended-ring structures have been synthesized through linear combinations of azaacenes and pyrene. Importantly, these extended systems demonstrate enhanced chemical stability and allow for the construction of macromolecular-sized structures. In this report we present a combined quantum-chemical and experimental study to reveal the cost of these improved characteristics in fully carbon-based systems. The results clearly show that pyrene moieties inserted among acene units do not result in long acene-like structures, rather the pyrene-inserted acene is, electronically, a series of (nearly) isolated acenes. The origin of pyrene's electronic blocking effect and implications on oxidized and photoexcited states of these extended-ring systems are detailed. The results of this investigation definitively show that coupling pyrene in an orthogonal orientation (through the 4, 5/9, 10 positions or e/l faces) to acenes should be eschewed if nanographene-/nanowire-like structures are desired.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Processing Dependent Influence of the Hole Transport Layer Ionization Energy on Methylammonium Lead Iodide Perovskite Photovoltaics

Organometal halide perovskite photovoltaics typically contain both electron and hole transport layers, both of which influence charge extraction and recombination. The ionization energy (IE) of the hole transport layer (HTL) is one important material property that will influence the open-circuit voltage, fill factor, and short-circuit current. Herein, we introduce a new series of triarylaminoethynylsilanes with adjustable IEs as efficient HTL materials for methylammonium lead iodide (MAPbI 3 ) perovskite based photovoltaics. The three triarylaminoethynylsilanes investigated can all be used as HTLs to yield PV performance on par with the commonly used HTLs PEDOT:PSS and Spiro-OMeTAD in inverted architectures (i.e., HTL deposited prior to the perovskite layer). We further investigate the influence of the HTL IE on the photovoltaic performance of MAPbI 3 based inverted devices using two different MAPbI 3 processing methods with a series of 11 different HTL materials, with IEs ranging from 4.74 to 5.84 eV. The requirements for the HTL IE change based on whether MAPbI 3 is formed from lead acetate, Pb(OAc) 2 , or PbI 2 as the Pb source. The ideal HTL IE range is between 4.8 and 5.3 eV for MAPbI 3 processed from Pb(OAc) 2 , while with PbI 2 the PV performance is relatively insensitive to variations in the HTL IE between 4.8 and 5.8 eV. Finally, our results suggest that contradictory findings in the literature on the effect of the HTL IE in perovskite photovoltaics stem partly from the different processing methods employed.

36 MATERIALS SCIENCE↗