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This paper discusses the advantages of OLEDs in pixel scaling and the novel device structures enabled by photolithography. We show the pixel layouts that can be realized by photolithographic patterning, i.e., delta and color strip pixel layout with high pixel density. Further integration of OPD next to an OLED pixel is discussed. Finally, we show the OLED performance after three times OLED patterning steps, which is crucial for the full‐color OLED display realized by photolithography patterning processes. The results suggest that the photolithography patterning process could be a powerful method to further enhance the AMOLED display performance. [ABSTRACT FROM AUTHOR]

Resolution and brightness are the essential figure‐of‐merits for the microdisplay development needed for AR and VR applications. In this presentation, we show our technology development toward high‐resolution FMM‐free direct R‐G‐B OLED microdisplays. We show the schematic fabrication setup and integration route to fabricate red, green, and blue OLED pixels side‐by‐side by the OLED photolithographic patterning processes. We demonstrate a 1µm line and space feature with the photoresist and transfer the pattern to an OLED stack. With the high resolution of photoresist, high aperture ratio, and high‐resolution multicolor OLED pixel arrays are demonstrated. We also investigate the possible OLED degradations induced in the photolithography process. With the innovations in the process steps, OLED stacks, process environments, and photoresists, we demonstrate a breakthrough in the reliability of photolithography patterned OLED. [ABSTRACT FROM AUTHOR]

Going towards high‐resolution, uniform displays with a high‐brightness range requires optimizations on different topics. This work presents an overview on this subject. To achieve a good uniformity, a compensation method is proposed using a 2T1C pixel circuit, compatible with high‐resolution requirements, improving uniformity by a factor 52.5. In order to further increase the achievable resolution, a new technology stack, using a planar and a vertical TFT is introduced. For increasing the brightness range, a global dimming method, compatible with the 2T1C pixel circuit, is demonstrated. [ABSTRACT FROM AUTHOR]

Photo-induced electron transfer between poly-(3-hexylthiophene) (P3HT) and small (2.4 nm) PbS quantum dots (QDs), capped by different ligands, was studied by picosecond and femtosecond time-resolved fluorescence and by photo-induced absorption (PIA) measurements. In line with previous experiments, we observed that the efficiency of the quenching of P3HT by PbS QDs increased upon decreasing the average thickness of the ligand shell. This trend was also observed in the PIA spectra and in prior work on the performance of photovoltaic devices where the active layer was a blend of P3HT with PbS QDs capped by different ligands. Combining the pico- and femtosecond fluorescence decays showed that the quenching in blend films of P3HT and PbS QDs treated with 1,4-benzenedithiol occurred over a broad time scale ranging from tens of femtoseconds to hundreds of picoseconds. This complex kinetics was attributed to exciton hopping followed by electron transfer to the conduction band of the QDs. We also compared the wavelength dependence of the internal quantum efficiency (IQE) in the hybrid photovoltaic devices to those devices where the photoactive layer consists of PbS QDs only. Although excitation in the first excitonic transition of the PbS QDs yielded a similar IQE in both devices, the IQE of the hybrid devices tripled at wavelengths where also P3HT started to absorb. This suggests that upon excitation of P3HT in the latter devices, charge generation occurs by photo-induced electron transfer from P3HT to the QDs rather than by energy transfer to the QDs followed by exciton dissociation in the QDs. [ABSTRACT FROM AUTHOR]

Photo-induced electron transfer between poly-(3-hexylthiophene) (P3HT) and small (2.4 nm) PbS quantum dots (QDs), capped by different ligands, was studied by picosecond and femtosecond time-resolved fluorescence and by photo-induced absorption (PIA) measurements. In line with previous experiments, we observed that the efficiency of the quenching of P3HT by PbS QDs increased upon decreasing the average thickness of the ligand shell. This trend was also observed in the PIA spectra and in prior work on the performance of photovoltaic devices where the active layer was a blend of P3HT with PbS QDs capped by different ligands. Combining the pico- and femtosecond fluorescence decays showed that the quenching in blend films of P3HT and PbS QDs treated with 1,4-benzenedithiol occurred over a broad time scale ranging from tens of femtoseconds to hundreds of picoseconds. This complex kinetics was attributed to exciton hopping followed by electron transfer to the conduction band of the QDs. We also compared the wavelength dependence of the internal quantum efficiency (IQE) in the hybrid photovoltaic devices to those devices where the photoactive layer consists of PbS QDs only. Although excitation in the first excitonic transition of the PbS QDs yielded a similar IQE in both devices, the IQE of the hybrid devices tripled at wavelengths where also P3HT started to absorb. This suggests that upon excitation of P3HT in the latter devices, charge generation occurs by photo-induced electron transfer from P3HT to the QDs rather than by energy transfer to the QDs followed by exciton dissociation in the QDs. [ABSTRACT FROM AUTHOR]

The charge carrier transport in thin film hybrid solar cells is analyzed and correlated with device performance and the mechanisms responsible for recombination loss. The hybrid bulk heterojunction consisted of a blend of poly(3-hexylthiophene) (P3HT) and small size (2.4 nm) PbS quantum dots (QDs). The charge transport in the P3HT:PbS blends was determined by measuring the space-charge limited current in hole-only and electron-only devices. When the loading of PbS QDs exceeds the percolation threshold, a significant increase of the electron mobility is observed in the blend with PbS QDs. The hole mobility, on the other hand, only slightly decreased upon increasing the loading of PbS QDs. We also showed that the photocurrent is limited by the low shunt resistance rather than by space-charge effects. The significant reduction of the fill factor at high light intensity suggests that under these conditions the non-geminate recombination dominates. However, at open-circuit conditions, the trap-assisted recombination dominates over nongeminate recombination. [ABSTRACT FROM AUTHOR]

Two different external compensation methods for high‐resolution active matrix organic light‐emitting diode (AMOLED) displays are presented and compared. Both compensation methods are implemented using a small pixel circuit, namely, a 3T2C and a 2T1C pixel circuit, allowing high‐resolution displays. Due to the simple driving schemes, these methods allow fast driving, even for large displays. The characterization results show a significant improvement in current variation by implementing either of these methods. The VT compensation method using a 3T2C pixel circuit is able to reduce the current variation down to 0.56%, whereas the VT‐ and β‐factor compensation method using a 2T1C pixel circuit demonstrates a further reduction in current variations down to 0.079%. This method also clearly shows significant improvement in optical variation between neighboring pixels. [ABSTRACT FROM AUTHOR]

Resolution, power efficiency, and brightness are crucial features in microdisplays for upcoming VR and AR applications. This presentation shows our work towards a high‐resolution direct RGB microdisplay. An IGZO TFTs with a top gate length of 80 nm is realized with 300mm facilities for high‐resolution backplane developments. For the development of high‐resolution OLED enabled by photolithographic patterning, we investigate an excess driving voltage in photolithographic patterned OLEDs caused by contaminants at the organic semiconductor interface. With necessary mitigation, we reduce the excess driving voltage and observe no significant lifetime change after multiple photolithographic patterning steps. [ABSTRACT FROM AUTHOR]

We apply a photolithographic patterning process to integrate a green phosphorescent organic light emitting diode (OLED) with a polymer‐based organic photodetector (OPD) side‐by‐side with resolution up to 635 ppi. The characteristics of OLED and OPD before and after patterning are investigated. The crosstalk between OLED and OPD subpixels and the linearity of the integrated OPD under different luminance are also studied. The results indicate that photolithography enabled integration is an encouraging route of organic and hybrid electronics (OHEs) manufacturing. [ABSTRACT FROM AUTHOR]

Different approaches of surface modification of the quantum dots (QDs), namely, solution-phase (octylamine, octanethiol) and post-deposition (acetic acid, 1,4-benzenedithiol) ligand exchange were used in the fabrication of hybrid bulk heterojunction solar cell containing poly (3-hexylthiophene) (P3HT) and small (2.4 nm) PbS QDs. We show that replacing oleic acid by shorter chain ligands improves the figures of merit of the solar cells. This can possibly be attributed to a combination of a reduced thickness of the barrier for electron transfer and an optimized phase separation. The best results were obtained for post-deposition ligand exchange by 1,4-benzenedithiol, which improves the power conversion efficiency of solar cells based on a bulk heterojunction of lead sulfide (PbS) QDs and P3HT up to two orders of magnitude over previously reported hybrid cells based on a bulk heterojunction of P3HT:PbS QDs, where the QDs are capped by acetic acid ligands. The optimal performance was obtained for solar cells with 69 wt.% PbS QDs. Besides the ligand effects, the improvement was attributed to the formation of an energetically favorable bulk heterojunction with P3HT, when small size (2.4 nm) PbS QDs were used. Dark current density-voltage (J-V) measurements carried out on the device provided insight into the working mechanism: the comparison between the dark J-V characteristics of the bench mark system P3HT:PCBM and the P3HT:PbS blends allows us to conclude that a larger leakage current and a more efficient recombination are the major factors responsible for the larger losses in the hybrid system. [ABSTRACT FROM AUTHOR]

Smartphone displays are leading the transformation from LCD to AMOLED. New form factors require deeper integration of functionalities other than light emission into the panel. Scaling, photolithography, new materials and novel device architectures enable inclusion of new functionalities into displays, such as light sensing, biometrics and user interactions. [ABSTRACT FROM AUTHOR]

This paper presents a new compensation principle using a 2T1C pixel circuit. The implementation shows significant improvement in uniformity for all grey‐levels, due to compensation for both VT and β‐factor variations. The resulting current variation after compensation in the characterized display area reaches values down to 0.079%. [ABSTRACT FROM AUTHOR]

Patterning organic materials by photolithography enables not only high‐resolution, side‐by‐side RGB OLED arrays, but also the introduction of organic photodetector in the same frontplane. We show patterned active matrix displays processed on flexible backplane. Furthermore, we demonstrate OPD patterning proof‐of‐concept. These are the building blocks allowing in‐cell optical fingerprint sensor. [ABSTRACT FROM AUTHOR]

High resolution RGB OLED frontplane is a key enabler for direct‐view transparent AR displays. 1250 ppi passive displays and semi‐transparent active displays are shown. T90 lifetime at 1000 nit is above 150 hours after patterning. OLED photolithography can provide pixel density above 1000 ppi while keeping high aperture ratio. [ABSTRACT FROM AUTHOR]

Abstract: High‐resolution RGB organic light‐emitting diode frontplane is a key enabler for direct‐view transparent augmented reality displays. In this paper, we demonstrate 1250 ppi passive displays and semi‐transparent active displays. Organic light‐emitting diode photolithography can provide pixel density above 1000 ppi while keeping effective emission area high because of high aperture ratio. Patterns with 2 μm line pitch were successfully transferred to emission layers, indicating possible further pixel density scaling. Lifetime after patterning, key parameter enabling industrialization, is above 150 h (T90 at 1000 nit). [ABSTRACT FROM AUTHOR]

We investigated the limitations of the field plate (FP) effect on breakdown voltage VBD that is due to the silicon substrate in AlGaN/GaN/AlGaN double heterostructures field-effect transistors. In our previous work, we showed that in devices with large gate–drain distance (LGD > \8\ \mu\m), the breakdown voltage does not linearly increase with LGD because of a double leakage path between the silicon substrate and the metal contacts, which makes the device break at the silicon interface. In this paper, we showed that the effect of the FP for such large LGD is not significant because the breakdown is still dominated by the silicon substrate. The increase in VBD due to the FP is significant only for devices with small gate–drain distances (LGD < \8\ \mu\m). Indeed we show that for such small LGD the increase in the breakdown voltage is more than double, whereas for larger LGD, this is only about 10%. Simulations of AlGaN/GaN/AlGaN devices for small LGD are carried out with different FP lengths and passivation thickness in order to study the electric field distribution. [ABSTRACT FROM AUTHOR]