OLED-on-silicon for near-to-eye microdisplays and sensing

Smart eyewear featuring near-to-eye (NTE) displays have evolved as major devices for wearable displays, which hold potential to become adopted by consumers soon. Tiny OLED-on-silicon microdisplays (<1” screen diagonal) are a key component of eyewear displays, creating images from active-matrix organic light emitting diodes (AM-OLED), similar to those that have become popular in mobile phone displays

P‐102: Amorphous Silicon Thin‐Film Transistors‐based Active‐Matrix Organic Light‐Emitting Displays

In this paper, we describe hydrogenated amorphous silicon (a‐Si:H) thin‐film transistor (TFT)‐based active‐matrix arrays for active‐matrix organic light‐emitting displays (AM‐OLEDs). The proposed pixel electrode circuits based on three a‐Si:H TFTs can supply a continuous output current for AM‐OLEDs. Each pixel circuit has compensation circuits that can adjust for the OLED and a‐Si:H TFTs electrical characteristics shifts.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92089/1/1.1830416.pd

70.3: Current‐Scaling a‐Si:H TFT Pixel Electrode Circuit for AM‐OLEDs

We fabricated and characterized the amorphous silicon thin‐film transistor (a‐Si:H TFT) pixel electrode circuit with currentscaling function that can be used for active‐matrix organic lightemitting displays (AM‐OLEDs). As expected from previously reported simulation results, fabricated circuit showed an acceptable current‐scaling performance for a high‐resolution AM‐OLED based on a‐Si:H TFTs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92085/1/1.2451422.pd

P‐143: A Novel Current‐Scaling a‐Si:H TFTs Pixel Electrode Circuit for Active‐Matrix Organic Light‐Emitting Displays

Hydrogenated amorphous silicon thin‐film transistor (a‐Si:H TFT) pixel electrode circuit with a function of current scaling is proposed for active‐matrix organic light‐emitting displays (AM‐OLEDs). In contrast to the conventional current mirror pixel electrode circuit, in this circuit a high data‐to‐organic light‐emitting device (OLED) current ratio can be achieved, without increasing the a‐Si:H TFT size, by using a cascade structure of storage capacitors. Moreover, the proposed circuit can compensate for the variations of TFT threshold voltage. Simulation results, based on a‐Si:H TFT and OLED experimental data, showed that a data‐to‐OLED current ratio larger than 10 and a fast pixel programming time can be accomplished with the proposed circuit.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92010/1/1.2036579.pd

Three-Dimensional Profiling of OLED by Laser Desorption Ionization-Mass Spectrometry Imaging

Organic light emitting devices (OLEDs), especially in a screen display format, present unique and interesting substrates for Laser Desorption/Ionization - Mass Spectrometry Imaging (LDI-MSI) analysis. These devices contain many compounds that inherently absorb light energy and do not require an additional matrix to induce desorption and ionization. OLED screens have lateral features with dimensions that are tens of microns in magnitude and depth features that are tens to hundreds of nanometers thick. Monitoring the chemical composition of these features is essential, as contamination and degradation can impact device lifetime. This work demonstrates the capability of LDI-MSI to obtain lateral and partial depth resolved information of multicolored OLED displays and suggests the application to other mixed organic electronics with minimal sample preparation. This was realized when analyzing two different manufactured OLEDs, in an active-matrix display format, with-out the need to remove the cathode. By utilizing low laser energy and high lateral spatial resolution imaging (10 µm), depth profiling can be observed while maintaining laterally resolved information resulting in a three-dimensional MSI approach that would complement existing OLED characterization methods

Intrinsically stretchable and transparent thin-film transistors based on printable silver nanowires, carbon nanotubes and an elastomeric dielectric.

Thin-film field-effect transistor is a fundamental component behind various mordern electronics. The development of stretchable electronics poses fundamental challenges in developing new electronic materials for stretchable thin-film transistors that are mechanically compliant and solution processable. Here we report the fabrication of transparent thin-film transistors that behave like an elastomer film. The entire fabrication is carried out by solution-based techniques, and the resulting devices exhibit a mobility of ∼30 cm(2) V(-1) s(-1), on/off ratio of 10(3)-10(4), switching current &gt;100 μA, transconductance &gt;50 μS and relative low operating voltages. The devices can be stretched by up to 50% strain and subjected to 500 cycles of repeated stretching to 20% strain without significant loss in electrical property. The thin-film transistors are also used to drive organic light-emitting diodes. The approach and results represent an important progress toward the development of stretchable active-matrix displays

Quantitative analysis of pixel crosstalk in AMOLED displays

The resolution of organic light-emitting diode (OLED) displays is increasing steadily as these displays are adopted for mobile and virtual reality (VR) devices. This leads to a stronger pixel crosstalk effect, where the neighbors of active pixels unintentionally emit light due to a lateral electric current between the pixels. Recently, the crosstalk was quantified by measuring the current flowing through the common hole transport layer between the neighboring pixels and comparing it to the current through the active pixel diode. The measurements showed that the crosstalk is more crucial for low light levels. In such cases, the intended and parasitic currents are similar. The simulations performed in this study validated these measurement results. By simulations, we quantify the crosstalk current through the diode. The luminous intensity can be calculated with the measured current efficiency of the diodes. For low light levels, the unintended luminance can reach up to 40% of the intended luminance. The luminance due to pixel crosstalk is perceivable by humans. This effect should be considered for OLED displays with resolutions higher than 300 PPI