The Impact of Local Work Function Variations on Fermi Level Pinning of Organic Semiconductors

2013 ◽  
Vol 117 (43) ◽  
pp. 22285-22289 ◽  
Author(s):  
Stefanie Winkler ◽  
Johannes Frisch ◽  
Raphael Schlesinger ◽  
Martin Oehzelt ◽  
Ralph Rieger ◽  
...  
Keyword(s):  
Fermi Level ◽  
Work Function ◽  
Organic Semiconductors ◽  
Fermi Level Pinning ◽  
The Impact ◽  
Local Work

Investigations of Metal Gate Electrodes on HfO2 Gate Dielectrics

2004 ◽  
Vol 811 ◽  
Author(s):  
Jamie Schaeffer ◽  
Sri Samavedam ◽  
Leonardo Fonseca ◽  
Cristiano Capasso ◽  
Olubunmi Adetutu ◽  
...  
Keyword(s):  
Fermi Level ◽  
Work Function ◽  
Gate Dielectrics ◽  
Electrical Stability ◽  
Metal Gate ◽  
Fermi Level Pinning ◽  
Poly Silicon ◽  
Metal Work Function ◽  
The Impact ◽  
Metal Work

ABSTRACTAs traditional poly-silicon gated MOSFET devices scale, the additional series capacitance due to poly-silicon depletion becomes an increasingly large fraction of the total gate capacitance, excessive boron penetration causes threshold voltage shifts, and the gate resistance is elevated. To solve these problems and continue aggressive device scaling we are studying metal electrodes with suitable work-functions and sufficient physical and electrical stability. Our studies of metal gates on HfO2 indicate that excessive inter-diffusion, inadequate phase stability, and interfacial reactions are mechanisms of failure at source drain activation temperatures that must be considered during the electrode selection process. Understanding the physical properties of the metal gate – HfO2 interface is critical to understanding the electrical behavior of MOS devices. Of particular interest is Fermi level pinning, a phenomenon that occurs at metal – dielectric interfaces which causes undesirable shifts in the effective metal work function. The magnitude of Fermi level pinning on HfO2 electrodes is studied with Pt and LaB6 electrodes. In addition, the intrinsic and extrinsic contributions to Fermi level pinning of platinum electrodes on HfO2 gate dielectrics are investigated by examining the impact of oxygen and forming gas anneals on the work function of platinum-HfO2-silicon capacitors. The presence of interfacial oxygen vacancies or Pt-Hf bonds is believed to be responsible for a degree of pinning that is stronger than predicted from the MIGS model alone. Interface chemistry and defects influence the effective metal work function.

Fermi Level Pinning by Gap States in Organic Semiconductors

2013 ◽  
Vol 110 (3) ◽  
Author(s):  
S. Yogev ◽  
R. Matsubara ◽  
M. Nakamura ◽  
U. Zschieschang ◽  
H. Klauk ◽  
...  
Keyword(s):  
Fermi Level ◽  
Organic Semiconductors ◽  
Fermi Level Pinning ◽  
Gap States

Decoupling the Fermi-level pinning effect and intrinsic limitations on p-type effective work function metal electrodes

2008 ◽  
Vol 85 (1) ◽  
pp. 2-8 ◽  
Author(s):  
Huang-Chun Wen ◽  
Prashant Majhi ◽  
Kisik Choi ◽  
C.S. Park ◽  
Husam N. Alshareef ◽  
...  
Keyword(s):  
Fermi Level ◽  
Work Function ◽  
Metal Electrodes ◽  
Effective Work ◽  
Effective Work Function ◽  
Fermi Level Pinning ◽  
Pinning Effect ◽  
P Type

scholarly journals Improving organic photovoltaic cells by forcing electrode work function well beyond onset of Ohmic transition

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chao Zhao ◽  
Cindy G. Tang ◽  
Zong-Long Seah ◽  
Qi-Mian Koh ◽  
Lay-Lay Chua ◽  
...  
Keyword(s):  
Solar Cells ◽  
Fermi Level ◽  
Work Function ◽  
Organic Solar Cells ◽  
Carrier Mobility ◽  
Fill Factor ◽  
Open Circuit Voltage ◽  
Open Circuit ◽  
Fermi Level Pinning ◽  
Electrode Contact

AbstractAs electrode work function rises or falls sufficiently, the organic semiconductor/electrode contact reaches Fermi-level pinning, and then, few tenths of an electron-volt later, Ohmic transition. For organic solar cells, the resultant flattening of open-circuit voltage (Voc) and fill factor (FF) leads to a ‘plateau’ that maximizes power conversion efficiency (PCE). Here, we demonstrate this plateau in fact tilts slightly upwards. Thus, further driving of the electrode work function can continue to improve Voc and FF, albeit slowly. The first effect arises from the coercion of Fermi level up the semiconductor density-of-states in the case of ‘soft’ Fermi pinning, raising cell built-in potential. The second effect arises from the contact-induced enhancement of majority-carrier mobility. We exemplify these using PBDTTPD:PCBM solar cells, where PBDTTPD is a prototypal face-stacked semiconductor, and where work function of the hole collection layer is systematically ‘tuned’ from onset of Fermi-level pinning, through Ohmic transition, and well into the Ohmic regime.

Interface Fermi Level Pinning at Contacts Between PEDOT: PSS and Molecular Organic Semiconductors

ChemPhysChem ◽  
2007 ◽  
Vol 8 (3) ◽  
pp. 386-390 ◽  
Author(s):  
Heiko Peisert ◽  
Andreas Petr ◽  
Lothar Dunsch ◽  
Thomas Chassé ◽  
Martin Knupfer
Keyword(s):  
Fermi Level ◽  
Organic Semiconductors ◽  
Fermi Level Pinning
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