![Brian Kim
EQE: formula
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• h Plank’s constant 6.626 ×10−34 J · s [note that 1Joule 1W.s]
• c speed of light 2.998 ×108 m/s
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Calculating current efficiency using EQE.pdf
- 1. Calculating current efficiency using EQE APR.4, 2025 BRIAN KIM, PHD 1
- 2. Brian Kim Why did I create this formula? 2 We often see announcements that high EQE is achieved without defining the dominant wavelength. However, this does not necessarily guarantee that an efficient display system is achieved. This is because the emission wavelength must satisfy the color gamut, and the EQE does not include information on the dominant wavelength, which is directly related to the photometric power. The following formula is designed to estimate efficiency using EQE.
- 3. Brian Kim Efficiency of device and system 3 From a system point of view, power efficiency is important. Requires lower series resistance to reduce IR drop: ITO, contacts for n-side and p-side. A local cathode design in every pixel is better solution than a common cathode design. In addition, the Vth variation in the LED must be suppressed. (cause the higher Vdd to operate in the saturation region) · · ⁄ · ⁄ · · Current efficiency (device level efficiency) Power efficiency (system level efficiency) n-GaN p-GaN hν Id Id hν ~1V 2~2.5V 2~4V Sidewall damage: Light leaky & carrier losses P-contact: Resistance & reflectance Backplane TRs ⁄ ⁄
- 4. Brian Kim EQE: formula 4 Wherein: # / ! # " #! ! ! ! $ / ! % ! $ " • & 'ℎ)*+& ,- ). &/&'0*,. 1.602 × 10789 : · ; [.,0& 0ℎ)0 1=,/>?@ 1: · 1;&'] • h Plank’s constant 6.626 ×10−34 J · s [note that 1Joule 1W.s] • c speed of light 2.998 ×108 m/s • ∴ ]^ _ 8.9`ab×8cdef 8.acg×8cdeh 1.23995 × 107a • jkj >.l0 >.l0/&;;, n o p ·q r · r·s t·q u $u " ! $" v!$ uwx. $u " ! $" v!$ u $$! u$x! ! ! $ $u " ! $" v!$ uwx. " ! $u " ! $" v!$ × uwx. " × ! $u " ! $" v!$× uwx. y z{.{| × " n-GaN p-GaN hν Id Id hν
- 5. Brian Kim 5 Internal quantum efficiency (IQE) Defines ‘the number of photons generated relative to the number of electrons’ inside the LED. The key is how efficiently electrons and holes generate photons. The controlling factors are defects in the epi structure, band structure (e.g., band bending due to piezoelectric polarization caused by strain), and sidewall damage etc. Light extraction efficiency (LEE) Defines how efficiently photons created inside a LED can be emitted into the air. The governing parameters are the geometry of the die and the reflectivity of the p-side reflector etc. EQE: IQE x LEE Internal Quantum Efficiency (IQE) Light Extraction Efficiency (LEE) External Quantum Efficiency (EQE) x = n-GaN p-GaN hν Id Id hν
- 6. Brian Kim Current efficiency conversion from EQE 6 The current efficiency can be calculated by using EQE and peak wavelength (peak). The equation was derived by the following equations: 1. EQE equation 2. Photometric power equation Efficiency calculation If we know EQE value and their peak wavelength of the radiometric spectrum, the efficiency (cd/A) can be (EQE) x (Y-axis value at peak wavelength). - As a first approximation, a dominant wavelength is fine. Red LED may not good to use the dominant wavelength instead of the peak wavelength due to long tail… - ex) Green EQE=10% @525nm is "10 x 4.018" cd/A, where multiplication factor @ 525 nm is 4.018 Please see the next page to see the multiplication factor based on the wavelength change. ∅w ~•z € v • %! ‚•ƒ z•ƒ „ 525 nm
- 7. Brian Kim Multiplication factor based on the wavelength 7 Multiplication factor wavelength 1.21447E-06 390 0.002657149 400 0.007921041 410 0.0255618 420 0.072405284 430 0.140299423 440 0.226647957 450 0.350085517 460 0.519551735 470 0.777350303 480 1.139435477 490 1.733856868 500 2.647149896 510 3.664677234 520 4.365280158 530 4.74171383 540 4.855336029 550 4.768873242 560 4.482732439 570 4.02598344 580 3.44369431 590 2.822661723 600 2.213190897 610 1.649354506 620 1.128979483 630 0.733903231 640 0.441825875 650 0.248065646 660 0.128190518 670 0.067099724 680 0.031935579 690 0.015728175 700 0.007904537 710 0.003902967 720 0.001911883 730 0.000903126 740 0.000429438 750 0.000211894 760 0.000104571 770 400 0.002657149 401 0.003195352 402 0.003730878 403 0.004263746 404 0.004793976 405 0.005321588 406 0.005846601 407 0.006369033 408 0.006888905 409 0.007406235 410 0.007921041 411 0.009723746 412 0.0115177 413 0.013302967 414 0.015079609 415 0.01684769 416 0.01860727 417 0.02035841 418 0.022101172 419 0.023835616 420 0.0255618 421 0.030346288 422 0.035108102 423 0.039847401 424 0.044564345 425 0.049259092 426 0.053931797 427 0.058582616 428 0.063211703 429 0.067819208 430 0.072405284 431 0.079336472 432 0.086235571 433 0.093102804 434 0.099938391 435 0.106742549 436 0.113515496 437 0.120257446 438 0.12696861 439 0.1336492 440 0.140299423 441 0.149110498 442 0.157881704 443 0.16661331 444 0.175305585 445 0.183958794 446 0.192573199 447 0.201149061 448 0.209686638 449 0.218186185 450 0.226647957 451 0.23923804 452 0.251772416 453 0.264251452 454 0.276675514 455 0.289044965 456 0.301360164 457 0.313621467 458 0.325829227 459 0.337983795 460 0.350085517 461 0.367362984 462 0.384565656 463 0.401694019 464 0.418748553 465 0.435729735 466 0.452638035 467 0.469473923 468 0.486237863 469 0.502930315 470 0.519551735 471 0.545824201 472 0.571985342 473 0.598035866 474 0.623976471 475 0.649807854 476 0.6755307 477 0.701145695 478 0.726653513 479 0.752054827 480 0.777350303 481 0.814236318 482 0.85096928 483 0.887550138 484 0.923979836 485 0.960259308 486 0.996389482 487 1.032371277 488 1.068205606 489 1.103893374 490 1.139435477 491 1.199967187 492 1.260252833 493 1.320293912 494 1.38009191 495 1.439648301 496 1.498964544 497 1.558042091 498 1.616882378 499 1.675486832 500 1.733856868 501 1.823237451 502 1.912261935 503 2.000932446 504 2.089251089 505 2.177219956 506 2.264841119 507 2.352116637 508 2.450848239 509 2.549191899 510 2.647149896 511 2.750694752 512 2.853835137 513 2.956573414 514 3.058911932 515 3.160853018 516 3.262398984 517 3.363552123 518 3.464314708 519 3.564688999 520 3.664677234 521 3.735947781 522 3.806945261 523 3.87767124 524 3.948127272 525 4.018314901 526 4.088235656 527 4.157891057 528 4.227282612 529 4.296411818 530 4.365280158 531 4.403561548 532 4.441699024 533 4.479693394 534 4.517545464 535 4.55525603 536 4.592825885 537 4.630255815 538 4.667546601 539 4.704699016 540 4.74171383 541 4.75326507 542 4.764773686 543 4.776239913 544 4.787663984 545 4.799046132 546 4.810386588 547 4.821685579 548 4.832943333 549 4.844160075 550 4.855336029 551 4.851444002 552 4.847566076 553 4.843702175 554 4.839852223 555 4.836016145 556 4.822490956 557 4.809014331 558 4.79558601 559 4.782205732 560 4.768873242 561 4.739800112 562 4.710830446 563 4.681963691 564 4.6531993 565 4.624536731 566 4.595975442 567 4.567514899 568 4.539154569 569 4.510893924 570 4.482732439 571 4.436337619 572 4.39010502 573 4.34403379 574 4.298123088 575 4.252372074 576 4.206779919 577 4.161345795 578 4.116068883 579 4.070948368 580 4.02598344 581 3.96685253 582 3.90792482 583 3.849199262 584 3.790674819 585 3.73235046 586 3.67422516 587 3.616297902 588 3.558567676 589 3.501033477 590 3.44369431 591 3.380645316 592 3.317809326 593 3.255185262 594 3.192772053 595 3.130568636 596 3.068573956 597 3.006786963 598 2.945206615 599 2.883831878 600 2.822661723 601 2.760801956 602 2.699147702 603 2.63769794 604 2.576451654 605 2.515407836 606 2.454565482 607 2.393923597 608 2.333481191 609 2.273237284 610 2.213190897 611 2.155976729 612 2.098949537 613 2.042108403 614 1.98545242 615 1.928980684 616 1.872692297 617 1.816586369 618 1.760662014 619 1.704918351 620 1.649354506 621 1.596562837 622 1.543940916 623 1.491487926 624 1.439203055 625 1.387085495 626 1.335134444 627 1.283349107 628 1.231728692 629 1.180272411 630 1.128979483 631 1.088908358 632 1.04896404 633 1.009145928 634 0.969453426 635 0.929885939 636 0.890442878 637 0.851123658 638 0.811927695 639 0.772854411 640 0.733903231 641 0.704285403 642 0.674759841 643 0.645326117 644 0.615983802 645 0.58673247 646 0.5575717 647 0.528501072 648 0.499520168 649 0.470628573 650 0.441825875 651 0.422181981 652 0.402598344 653 0.383074688 654 0.363610737 655 0.344206218 656 0.324860859 657 0.30557439 658 0.286346543 659 0.26717705 660 0.248065646 661 0.235914915 662 0.223800892 663 0.211723413 664 0.199682311 665 0.187677424 666 0.175708587 667 0.163775638 668 0.151878417 669 0.140016763 670 0.128190518 671 0.121999498 672 0.115826905 673 0.109672654 674 0.103536666 675 0.097418859 676 0.091319151 677 0.085237463 678 0.079173716 679 0.073127829 680 0.067099724 681 0.063536837 682 0.059984398 683 0.056442362 684 0.052910683 685 0.049389315 686 0.045878214 687 0.042377334 688 0.038886631 689 0.03540606 690 0.031935579 691 0.030293729 692 0.028656624 693 0.027024244 694 0.025396569 695 0.023773577 696 0.022155249 697 0.020541565 698 0.018932504 699 0.017328048