Energy band and optical modeling of charge transport mechanism and photo-distribution of MoO₃/Al-doped MoO₃ in organic tandem cells

Abstract

The promising potential of achieving high efficiency organic tandem cells due to the widened absorption spectrum range has resulted in significant research in novel device concepts such as the modification of the recombination layer. In this study, a typically used charge transport interlayer in the recombination layer, MoO3, is modified by tuning the energy band and work function, with the help of an energy band model, to achieve energetic alignment without additional metallic layers. The energy level tuning is demonstrated by the co-evaporation of aluminum, which results in a doping effect. This shifts the work function of pristine MoO3 from 5.8[Formula: see text]eV to 4.3[Formula: see text]eV. The shift is proposed to be due to the formation of oxidized Al3+ and reduced MoO6+ that generates further mid-gap defect states and this shift increases with respect to Al concentration. The energy band shift changes the transport mechanism from hole-transporting to electron-transporting and the modification is modeled in this work. This suggests that recombination layer of MoO3/Al-MoO3 may have better energetic alignment and integrating this modified recombination layer results in improvement in the stacked device efficiency from 1.38% to 3.38% with enhancement in [Formula: see text], [Formula: see text] and fill factor. This enhancement is contributed from better aligned energy level and higher transparency of the recombination layer. The effective transparent recombination allows greater photon distribution to the top cell and increasing maximum matched photocurrent to the limiting subcell, thus improving photocurrent by 25% and overall efficiency up to 4.6%.

Quantum Effects Enter Semiconductor-Based SERS: Multiresonant MoO3·xH2O Quantum Dots Enabling Direct, Sensitive SERS Detection of Small Inorganic Molecules

“…The quantum size effect is observed directly via UV–vis spectroscopy (normalized absorption spectra given in Figure b), where a set of broad absorbance peaks attributable to the 1S h –1S e excitonic transition between the band gap can be clearly observed. Band gap energy discrepancies are derived to be 3.46, 3.1 and 2.8 eV for Mo-2 , Mo-10 and Mo-100 , respectively, fitting the reported bandgap of MoO 3 (∼3 eV). − The increase in bandgap as size reduces is a typical indication of quantum size effect where the energy band diverges into discrete energy states due to confined electron movement. , Correspondingly, photoluminescence (PL) spectra (Figure c,d) show significantly enhanced PL emissions from Mo-2 under 325 and 532 nm excitation, while weaker or no emission is observed from Mo-10 and Mo-100 . This suggests effectively increased number of photoexcited charge carriers on available energy states of the quantum-sized dots, while phonon scattering and nonradiative recombination processes are suppressed. − Moreover, the broad emission band profile of Mo-2 suggests the existence of several emissive states, which can be deconvoluted into 5 major bands using a typical Gaussian fit, namely 3.02 eV (410 nm, violet), 2.70 eV (459 nm, blue), 2.43 eV (510 nm, green), 2.18 eV (569 nm, yellow) and 1.94 eV (639 nm, red).…”

Controllable Electrically Guided Nano-Al/MoO3 Energetic-Film Formation on a Semiconductor Bridge with High Reactivity and Combustion Performance

“…The Al/MoO 3 MIC, as a desirable energetic system, has continuously aroused great interest, owing to its high heat of reaction (4698 J/g) and adiabatic flame temperature (3547 • C, higher than that of Al/Fe 2 O 3 , Al/CuO, etc.). Recently, different fabrication methods have been explored to prepare Al/MoO 3 MICs or nanothermites for developing their exothermic performances, including the thermal co-evaporation method [14], magnetron sputtering [15,16], sonic wave-assisted physical mixing [17], and arrested reactive milling laser irradiation [18]. For example, M.R.…”