Organic photodetectors (OPDs) exhibit superior spectral responses but slower photoresponse times compared to inorganic counterparts. Herein, we study the light-intensity-dependent OPD photoresponse time with two small-molecule donors (planar MPTA or twisted NP-SA) co-evaporated with C60 acceptors. MPTA:C60 exhibits the fastest response time at high-light intensities (>0.5 mW/cm2), attributed to its planar structure favoring strong intermolecular interactions. However, this blend exhibits the slowest response at low-light intensities, which is correlated with biphasic photocurrent transients indicative of the presence of a low density of deep trap states. Optical, structural, and energetical analyses indicate that MPTA molecular packing is strongly disrupted by C60, resulting in a larger (370 meV) HOMO level shift. This results in greater energetic inhomogeneity including possible MPTA-C60 adduct formation, leading to deep trap states which limit the low-light photoresponse time. This work provides important insights into the small molecule design rules critical for low charge-trapping and high-speed OPD applications.
Stacked
structures employing wavelength-selective organic photodiodes
(OPDs) have been studied as promising alternatives to the conventional
Si-based image sensors because of their color constancy. Herein, novel
donor (D)−π–acceptor (A) molecules are designed,
synthesized, and characterized as green-light-selective absorbers
for application in organic-on-Si hybrid complementary metal-oxide-semiconductor
(CMOS) color image sensors. The p-type molecules, combined with two
fused-type heterocyclic donors and an electron-accepting unit, exhibit
cyanine-like properties that are characterized by intense and sharp
absorption. This molecular design leads to improved absorption properties,
thermal stability, and higher photoelectric conversion compared to
those of a molecular design based on a nonfused ring. A maximum external
quantum efficiency of 66% (λmax = 550 nm) and high
specific detectivity (D*) of 8 × 1013 cm Hz1/2/W are achieved in an OPD consisting of a bulk
heterojunction blend with two transparent electrodes on both sides.
Finally, the green-light-detection capability of the narrow-band green-selective
OPD is demonstrated by the optical simulation of an organic-on-Si
hybrid, stacked-type, full-color photodetector comprising the green-light-selective
OPD and a bottom Si photodiode with only blue and red color filters.
Based on this molecular design, further optimization of the OPDs can
allow the development of various optoelectronic sensors including
3D-stacked image sensors with enhanced sensitivities to replace the
conventional Si-based CMOS image sensors.
Since the early nineties there have been a number of reports on the experimental development of Mg electrolytes based on organo/amide-magnesium chlorides and their transmetalations. However, there are no theoretical papers describing the underlying operating mechanisms of Mg electrolytes, and there is no clear understanding of these mechanisms. We have therefore attempted to clarify the operating mechanisms of Mg electrolytes by studying the characteristics of Mg complexes, solvation, chemical equilibrium, Mg-deposition processes, electrolyte-oxidation processes, and oxidative degradation mechanism of RMgCl-based electrolytes, using ab initio calculations. The formation and solvation energies of Mg complexes highly depend on the characteristics of R groups. Thus, changes in R groups of RMgCl lead to changes in the equilibrium position and the electrochemical reduction and oxidation pathways and energies. We first provide a methodological scheme for calculating Mg reduction potential values in non-aqueous electrolytes and electrochemical windows. We also describe a strategy for designing Mg electrolytes to maximize the electrochemical windows and oxidative stabilities. These results will be useful not only for designing improved Mg electrolytes, but also for developing new electrolytes in the future.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.