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  • 1

    Fraunhofer IPMS Bernd Richter/ 2010 -10

    Highly-efficient embedded organic light emitter for CMOS optoelectronics

    Bernd Richter, Uwe Vogel, Karsten Fehse, Rigo Herold, Thomas Presberger, Stephan Brenner, Lars Kroker

    Fraunhofer IPMS - Center for Organic Materials and Electronic Devices Dresden COMEDD

    Fraunhofer IPMSBernd Richter/ 2010 -10

    Outline

    Introduction

    OLED-on-CMOS: Applications

    OLED Microdisplays

    Technology

    Conclusion

    Fraunhofer IPMSBernd Richter/ 2010 -10

    transparent conductor

    organic layers

    metal cathode

    substrate

    Light emission +_

    bottom-emitting top-emitting

    Light emission

    (silicon wafer)

    Introduction to organic LEDs - OLEDs

    Lighting

    Medium and large display TFT

    OLED-on-CMOS

    Fraunhofer IPMSBernd Richter/ 2010 -10

    Introduction: OLED-on-CMOS (1)

    Top-emitting p-i-n OLED:

    highly-efficient OLED light sourcein/on CMOS

    based on small molecules(NOVALED AG)

    evaporated on Si-wafer

    sub-structuring by shadow mask >100m

    all colors monochrome, white, NIR

    doped charge transport layers

    low operating voltage

    transparent top electrode

    extremely thin (~100...300nm)

    excellent current and

    power efficiency(low-voltage, low-power)

    fast response time (MHz)-5 -4 -3 -2 -1 0 1 2 3 4 5

    10-6

    10-5

    10-4

    10-3

    10-2

    10-1

    100

    101

    102

    101

    102

    103

    104

    105

    orange emitter

    red emitter white emitter system

    Cu

    rren

    t de

    nsity [

    mA

    /cm

    ]

    Voltage [V]

    Lu

    min

    an

    ce

    [c

    d/m

    ]

    5.7

    11.6

    14.1

    Current

    efficiency[Cd/A]

    @100cd/m

    4.73.2white

    12.0003.22.5ora

    3.12.4red

    @1000cd/m

    @100cd/m

    lifetime

    @1000c

    d/m

    Voltage [V]

    (+)

    (-)

  • 2

    Fraunhofer IPMSBernd Richter/ 2010 -10

    Introduction: OLED-on-CMOS (2)

    CMOS top metal = OLED bottom electrode

    top metal definesOLED shape

    arbitrary shapes

    driving circuitry

    underneath

    Wafer

    FOX

    PMOS Photodiode

    Metal 1

    Metal 2

    Metal 3

    CMOS

    OLED

    TFE

    CMOS cross-section with OLED on top

    CMOS integration of electronic features

    driving

    acqusition

    processing

    control

    Co-integration of CMOS-compatible sensors

    embedded photodetectors

    temperature

    magnetic (Hall)

    MEMS,...

    Fraunhofer IPMSBernd Richter/ 2010 -10

    Example: OLED-on-CMOS testchip

    1.3 mm

    2 m

    4 m

    no active circuit, hardwired pattern (3 metals)

    separate deposition of monochrome RGB-OLED (shadow mask)

    pixel sub-structuring: shape of CMOS top metal

    ~60 mm

    Fraunhofer IPMSBernd Richter/ 2010 -10

    Outline

    Introduction

    OLED-on-CMOS: Applications

    OLED Microdisplays

    Technology

    Conclusion

    Fraunhofer IPMSBernd Richter/ 2010 -10

    OLED-on-CMOS: Applicationssensors

    optical sensors

    fluorescence, color, flowmetry, photoplethysmography,...

    light barriers (reflective)

    embedded illumination for image sensors

    patterned illumination possible

    optical finger-print, lab-on-chip,...

    opto-coupler

    microdisplays

    microdisplay

    HMD, mobile/micro-projection, electronic viewfinder,...

    bidirectional microdisplay(display + embedded image sensor)

    interactive HMD

    optical inspection,...

    iiii ARARARAR

    OLED CM OS DetektorOLED CM OS Detektor

  • 3

    Fraunhofer IPMSBernd Richter/ 2010 -10

    OLED-on-CMOS: Sensors

    CMOS photodetectors (PD) and embedded OLED illumination, excitation

    three types of optoelectronic sensors:

    reflection light barrier (top left)

    flow sensor (bottom left)

    color sensor (right)

    circuitry underneath OLED electrodes

    10,5

    3,5PD

    PD

    PD PD

    PD

    OLEDRed

    OLEDBlue

    OLEDGreen

    OLEDNIRPDPD PD PD PDPD PDPD

    OL ED1

    OLED2

    PD PD

    OLEDPDOLED PD PD PDPD

    Fraunhofer IPMSBernd Richter/ 2010 -10

    OLED-on-CMOS: Sensor applications

    Particle flow sensor

    OLED stripes for fluid illumination and 8 photodiodes

    light reflection depending on local fluid velocity and particle density

    analyzing photocurrents and correlation functions, the fluid particle velocity can be calculated

    Opto-coupler

    OLED Photodiodes

    Encapsulation

    CMOS Chip

    Capillary with flowing transparentfluid and reflecting particles

    Fraunhofer IPMSBernd Richter/ 2010 -10

    Outline

    Introduction

    OLED-on-CMOS: Applications

    OLED Microdisplays

    Technology

    Conclusion

    Fraunhofer IPMSBernd Richter/ 2010 -10

    time

    co

    mp

    lexit

    y

    Monochrome

    PM-Display

    MulticolorPM-Display

    Full colorPM-Display

    Full colorAM-Display

    Microdisplay See-throughMicrodisplay

    MobileProjection

    Display

    MobileFlexible

    Display

    iiii ARARARAR

    Mobile display driving forces:

    multimedia content

    information navigation by user interaction (touch screen,...)

    augmented-reality (AR)

    Mobile Display Dilemma

  • 4

    Fraunhofer IPMSBernd Richter/ 2010 -10

    OLED microdisplay: Overview

    line

    dri

    ver

    data driver

    video input, control

    RGB pixel

    data supply

    OLED microdisplay

    Physically very small, but

    high information content (TV quality)

    low power consumption

    enlarged image viewed through magnifying optics

    Active-matrix substrate

    data is stored inside pixel: analog/digital

    sub-pixel size: {(4x4), 4x12, 8x8, 36x36} m

    OLED pixel current: pA...nA

    sub-structuring of display pixel withmonochrome colors not possible

    combination of white OLEDs with colour filter

    Applications

    projection (rear, front, micro)

    near-to-eye (NTE)

    electronic viewfinder

    head mounted

    Fraunhofer IPMSBernd Richter/ 2010 -10

    OLED microdisplay: Pixel concept

    small pixel pitch (12um RGB)

    OLED: current driven pA...nA, Lum~ioled

    grayscale realization: analog / digital

    Increased number

    of transistors

    - no D/A

    conversion

    - stable storage of bits

    digital SRAM pixel cell

    many transistors + DRAM refresh

    necessary

    - no D/A

    conversion

    - simple linearity

    correction by PWM

    digital DRAM pixel cell

    pixel cell transistor matching is

    important

    shortprogramming

    duration

    voltage programmed

    long programming

    duration due to

    small currents

    pixel cell

    transistor

    matching is irrelevant

    current programmed

    (+subthreshold

    scaling)

    DisadvantageAdvantagePixel Cell Principle

    ZOOM

    iiii ARARARAR

    an

    alo

    gd

    igita

    l

    Dd

    ata

    display pixel

    Md1

    sa

    cat

    Md2Md3

    Md4

    OLED

    Cd

    em

    vref

    Fraunhofer IPMSBernd Richter/ 2010 -10

    OLED microdisplay: Hypoled

    full color VGA (640x480) OLED microdisplay

    pixel cell

    digital DRAM pixel cell

    luminance control by PWM

    sub-pixel: 4x12m

    24 bit parallel video interface

    50/60Hz frame rate

    configuration of color, contrast and gamma correction via IC

    high brightness

    up to 10,000 nits for monochrome green (micro-projection)

    1,000 nits for RGB color (HMD)

    0.18m CMOS foundry process

    core supply, digital I/O interface 1.8V

    negative OLED cathode voltage (max. -5.5V)

    active area 7.7x5.8mm

    chip size 12x11mm7.7mm

    5.8

    mm

    Fraunhofer IPMSBernd Richter/ 2010 -10

    Hypoled : Applications

    head-mounted display (HMD)

    RGB micro-projector

    MediaBox (DVB-T, DVB-H, WLAN)

  • 5

    Fraunhofer IPMSBernd Richter/ 2010 -10

    Bidirectional OLED microdisplay: Overview

    OLED CMOS detector

    CMOS wafer

    CMOS circuit

    encapsulation

    micro-optics

    "Bidirectional" functionality:

    OLED microdisplay + embedded image sensor

    nested display and camera pixel

    embedded CMOS photodiodes

    lower level than OLED

    side-by-side with active electronicsdevices

    local optical crosstalk possible

    emission and detection can be operated in parallel or sequentially

    line d

    river

    data driver

    video input, control

    displaydata

    OLED microdisplay

    cam readout

    line d

    river

    video output, control

    camdata

    embedded image sensor

    bidirectional microdisplay

    Fraunhofer IPMSBernd Richter/ 2010 -10

    Bidirectional OLED microdisplay: HMD appl.

    53 km/h Radio

    Navi

    Me

    n

    Display off

    -1

    30

    60

    conventional, unidirectional microdisplay

    displays an image

    OLED-on-CMOS microdisplay

    bidirectional microdisplay

    displays an image and detects anotherimage on the same device

    OLED-on-CMOS microdisplay + embeddedimage sensor

    HMD application: aimed at tracking the eyemovement with respect to

    user's sight (consciously and unconsciously)

    user's (situation) awareness (unconsciously)

    gaze-based human-display-interaction

    visual Input-/Output-Device (I/O) for person