PUI/MRSEC collaboration to create opportunities for women in materials-research

This three-year collaboration between a predominately undergraduate women's college (Simmons College) and a NSF-supported Materials Research Science and Engineering Center (the Cornell Center for Materials Research (CCMR)) focuses on establishing a collaborative Simmons/Cornell research program that provides opportunities for students to work with faculty on timely research projects, have access to sophisticated instrumentation, and gain related work experience in industrial settings. To interest women in participating in materials-related research and to encourage them to consider further career exploration in this area, the secondary goal of (he project focuses on augmenting women's undergraduate experience. In this regard, the project uses the PUI/MRSEC collaboration to enhance the undergraduate curriculum at Simmons and encourage new Ph.D.s in materials-related disciplines at Cornell to consider academic careers at Primarily Undergraduate Institutions (PUIs). To provide opportunities for students to work on research throughout their undergraduate careers, this program focuses on studying the degradation processes in organic light emitting diodes (OLEDs), These materials are currently of great interest for display applications, and an understanding and control of the degradation processes could ultimately influence their use in various types of consumer products. To widen science students' exposure to materials science, a new minor in materials was developed and materials science topics are being incorporated into physics and chemistry courses. To encourage students to consider graduate or industrial careers in materials science and to ease the transition into these large research environments, CCMR will place students in summer industrial jobs and REU positions. To provide students with further access to sophisticated instrumentation, a portion of the laboratory requirement for the new minor in materials will be co-taught during the summer by Simmons and Cornell collaborators at CCMR's Shared Experimental Facilities. Cornell's graduate students will participate in the program as mentors for Simmons undergraduates and will visit Simmons to better understand postgraduate teaching careers at PUIs. © 2003 Materials Research Society

Women in Materials: A collaborative effort between Simmons College and the Cornell Center for Materials Research

The Women in Materials program, supported by the National Science Foundation, is a collaboration between Simmons College, a predominately undergraduate women's college, and the Cornell Center for Materials Research. For the past four years, this program has provided unusual curricular and research opportunities for undergraduate women at Simmons College. This program demonstrates a successful model for enhancing undergraduate science and technology preparation through collaboration between primarily undergraduate institutions and NSF-supported Materials Research Science and Engineering Centers. © 2006 Materials Research Society

Current-induced degradation in polythiophene

The three-year collaboration between Simmons College and the Cornell Center for Materials Research (CCMR) is focused on undergraduate student/faculty research in organic light emitting diodes (OLEDs). The physics of OLED devices is characterized by three major processes: charge injection, charge transfer, and light emission as a result of the electron-hole recombination. In the first year of the program our research has been related to the first two stages. OLEDs based on small molecule as well as polymeric layers have been investigated, The devices were prepared using mostly aluminum (also nickel and iron) as electrodes and PC:TPD or polythiophene as the organic layer. Electrodes of about 20 nm were formed by vacuum evaporation, and organic layers of approximately 100-200 nm were spin-coated. The current-voltage characteristics, measured under forward and reverse bias up to 10 volts, demonstrate typical semiconductor S-shape behavior, and show variations dependent on aging, thickness of the polymer layer, and type and combination of electrodes. The results presented here specifically track the degradation of devices using polythiophene sandwiched between aluminum electrodes. The I-V curves and successive current response as a function of time and under constant voltage drive are presented along with complementary mass spectra and UV-visible and infrared absorption spectra. These measurements along with preliminary computer modeling of HOMO and LUMO energies for a series of thiophene oligomers suggest a correlation between internal changes in the polymer and variations in the electrical characteristics of the devices

Degradation in 1TMC OLEDs

The processes underlying degradation of organic light emitting diodes (OLEDs) are gradually becoming understood. In ruthenium-based ionic transition metal complex (iTMC) OLEDs, a dimeric species forms during device operation that quenches light emission [11. Water has been implicated in this degradation process [21. We report recent studies on degradation of OLEDs fabricated with fr(ppy)2(dtb-bpy)PF6 [ppy = 2-phenylpyridine, dtb-bpy = 4,4'-di-tert-butyl 2,2'- bipyridine [31. We have found that applying a thicker-than-usual metal electrode results in shorter turn-on times and higher light emission, though little improvement in lifetime. It appears that the degradation of these devices occurs by a different mechanism from that of the ruthenium-based devices and may involve local heating leading to chemical decomposition of the organic material. Observation of recurring but often transient dark-colored substances in both the Ru(bpy)3(PF6)2 and fr(ppy)2(dtb-bpy)PF6 systems, seen both in the solid state and in solution samples, may also be indicative of decomposition. © 2008 Materials Research Society

Degradation of Ru(bpy) <inf>3</inf>²⁺-based OLEDs

Analysis of the possible mechanisms of degradation of Ru(bpy) 32+-based OLEDs has led to the idea of quencher formation in the metalloorganic area close to the cathode. It has been suggested that the quencher results from an electrochemical process where one of the bipyridine (bpy) groups is replaced with two water molecules or from reduction of Ru(bpy) 32+ to Ru(bpy) 30. We have tested these and other degradation ideas for Ru(bpy) 32+-based OLEDs, both prepared and tested with considerable exposure to the ambient environment and using materials and procedures that emphasize cost of preparation rather than overall efficiency. In order to understand the mechanisms involved in these particular devices, we have correlated changes in the devices' electrical and optical properties with MALDI-TOF mass spectra and UV-vis absorption and fluorescence spectra. © 2005 Materials Research Society