We report on the latest progress in the field of organic p-i-n tandem solar cells. The external quantum efficiencies of a tandem solar cell with two complementary absorbing bulk heterojunctions with an efficiency of 6.07% (certified by Fraunhofer ISE) with an active area of about 2cm2 is analyzed. These solar cells are extremely stable: a reduction of only 3% of its initial power conversion efficiency was measured when stored at 85°C for 5000 hours. The solar cell does not show any reduction in efficiency when stored under continuous illumination of a tungsten lamp corresponding to 1.5 suns for 5000 hours. Furthermore, we present the latest results on optimized tandem solar cells showing a power
conversion efficiency of 7.66 % (certified by Fraunhofer ISE, active area of 1.1cm2).
Starting from a lab-curiosity, organic light emitting diodes have matured into a promising technology that has entered commercial markets. In particular for lighting applications, OLEDs can take advantage of their outstanding properties such as a high luminous efficacy, good color quality, and new design possibilities such
as illumination by
at light sources. In this contribution, new results on two approaches for highly efficient white OLEDs are presented: the all-phosphorescent concept and the triplet-harvesting approach.
We report on latest progress in the field of p-i-n type tandem solar cells. An optimized tandem cell architecture with two
complementary absorbing bulk heterojunctions leads to a certified power conversion efficiency of 5.9% on 2 cm2 active
area. Moreover, we show that p-i-n type tandem solar cells can be extremely stable: Extrapolated lifetimes corresponding
to more than 30 years of sun illumination have been achieved. Furthermore, we show that efficiency and stability only
slightly decrease when transferring the cell architecture to large serially interconnected modules of more than 100 cm²
A way to reach highly efficient and stable red bottom emission organic light emitting diodes (OLEDs) is the use
of doped transport layers, charge and exciton blockers, and phosphorescent emitter materials to combine low
operating voltage and high quantum yield. We will show how efficiency and lifetime of such devices can be
In our contribution, we report on highly efficient red p-i-n type organic light emitting diodes using an iridium-based
electrophosphorescent dye, Ir(MDQ)2(acac), doped in α-NPD as host material. By proper adjustment of
the hole blocking layer, the device performance may be enhanced to 20 % external quantum efficiency at an
operation voltage of 2.4 V and a brightness of 100 cd/m2. At the same time, a power efficiency of 37.5 lm/W is
reached. The quantum efficiency is well above previously reported values for this emitter. We attribute this high
efficiency to a combination of a well-adjusted charge carrier balance in the emission layer and a low current
density needed to reach a certain luminance due to the use of doped transport layers. High chemical stability of
the blocker material assures a long device lifetime of 32.000 hours at 1.000 cd/m2 initial luminance.
We present a novel organic light emitting device concept for white light generation with the potential for 100%
internal quantum efficiency, which employs fluorescent blue and phosphorescent green and orange emitters. Due
to its high triplet energy, the intrinsically non-radiative triplet excitons of the fluorescent blue emitter can still
be harvested for light emission by letting them diffuse to the phosphor-containing emission layers. Thus, all
electrically generated excitons can be used for light emission without the need for phosphorescent blue emitters,
which suffer from stability problems. We demonstrate the high potential of this concept in a device achieving
57.6 lmW-1 total external power efficiency at 100 cd m-2 (20.3% external quantum efficiency) and 37.5 lmW-1
(14.4%) at an illumination relevant brightness of 1,000 cd m-2, and a high color rendering index of 86.
We report on white organic light emitting diodes with three stacked emitter layers comprising the fluorescent
blue emitter Spiro-DPVBi, the phosphorescent green emitter system TCTA:Ir(ppy)3 and the phosphorescent red
emitter system NPB:Ir(MDQ)2(acac). A thin additional layer of mixed TCTA and TPBi separates the fluorescent
and phosphorescent emitting regions, simultaneously confining excitons efficiently and letting electrons and holes
easily pass. Furthermore, phosphorescence quenching by Dexter transfer to the non-radiative triplet state of
Spiro-DPVBi is suppressed. Devices were optimized to get color coordinates very close to the warm white
standard illuminant A. Best devices have a current efficiency of 13.8 cd/A, CIE color coordinates of (0.45, 0.42),
and a color rendering index of 91 at a brightness of 1000 cd/m2. Due to the use of electrically doped charge
transport layers, the voltage needed for 1000 cd/m2 was only 3.0 V, which leads to a power efficiency of 14.4 lm/W
assuming Lambertian emission.