White polymer light‐emitting devices with a peak forward‐viewing power efficiency close to 40 lm W−1, corresponding to an external quantum efficiency of 28.8% and a luminous efficiency of 60 cd A−1, are demonstrated. The devices are based on two newly synthesized yellow‐emitting iridium complexes functionalized with the sterically hindered diarylfluorene chromophores and are fabricated by a simple solution‐processing method.

A series of blue (B), green (G) and red (R) light-emitting, 9,9-bis(4-(2-ethylhexyloxy)phenyl)fl uorene (PPF) based polymers containing a dibenzothiophene-S,S -dioxide (SO) unit (PPF-SO polymer), with an additional benzothiadiazole (BT) unit (PPF-SO-BT polymer) or a 4,7-di(4-hexylthien-2-yl)benzothiadiazole (DHTBT) unit (PPF-SO-DHTBT polymer) are synthesized. These polymers exhibit high fl uorescence yields and good thermal stability. Light-emitting diodes (LEDs) using PPF-SO25, PPF-SO15-BT1, and PPF-SO15-DHTBT1 as emission polymers have maximum effi ciencies LE max = 7.0, 17.6 and 6.1 cd A − 1 with CIE coordinates (0.15, 0.17), (0.37, 0.56) and (0.62, 0.36), respectively. 1D distributed feedback lasers using PPF-SO30 as the gain medium are demonstrated, with a wavelength tuning range 467 to 487 nm and low pump energy thresholds ( ≥ 18 nJ). Blending different ratios of B (PPF-SO), G (PPF-SO-BT) and R (PPF-SO-DHTBT) polymers allows highly effi cient white polymer light-emitting diodes (WPLEDs) to be realized. The optimized devices have an attractive color temperature close to 4700 K and an excellent color rendering index (CRI) ≥ 90. They are relatively stable, with the emission color remaining almost unchanged when the current densities increase from 20 to 260 mA cm − 2 . The use of these polymers enables WPLEDs with a superior trade-off between device effi ciency, CRI, and color stability.

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Eight random and alternating copolymers PF-DTBTA derived from 2,7-fl uorene and 4,7-dithienylbenzotriazole (DTBTA) were synthesized. Thin solid fi lms of the energy-transfer copolymers possess high absolute photoluminescence (PL) quantum yields ( Φ PL ) between 60 − 72%. Inserting PVK layer between anode and emissive layer could show higher electroluminescence (EL) performances due to PVK-enhanced hole injection. Random copolymers PF-DTBTA1 − 15, with DTBTA molar contents from 1% to 15%, displayed yellow EL spectra with high external quantum effi ciency (EQE max ) up to 5.78%. PF-DTBTA50, the alternating copolymer, showed an orange EL with EQE max of 3.3%. The good Φ PL and EQE max of the PF-DTBTA50 with very high DTBTA content indicate that DTBTA is a high effi ciency chromophore with very low concentration quenching effects in the solid state PL and EL processes. PF-DTBTA0.03 − 0.1 could emit white EL due to partial energy transfer from fl uorene segments to DTBTA units. Moreover, white EL devices, with forward-viewing maximum luminous effi ciency up to 11 cd/A and stable white EL spectra (CIE coordinates of (0.33, 0.43)) in high current range from 5 mA to 60 mA, could be realized from the non-doped polymer with simple binary structure. Our results suggest that DTBTA has big potential to construct high performanced EL polymers or oligomers.

Novel poly[(fluorene)-co-(2,8-dioctyldibenzothiophene-S,S-dioxide-3,7-diyl)]s were synthesized. The octyl group on the 2,8-dioctyldibenzothiophene-S,S-dioxide (DOSO) unit improved the solubility of the polymers and broadened the optical band gap from 2.95 to 3.20 eV as the content of DOSO unit increases. The electroluminescence (EL) spectra of polymers show CIE coordinates around (0.16, 0.07) independent of the ratio of DOSO units in the polymers, owing to the ICT and steric hindrance dual-function. A high efficiency of 3.1 cd · A(-1) (EQE = 3.9%) was obtained with the configuration of ITO/PEDOT:PSS/polymer/Ba/Al. The results indicate that PF-3,7DOSOs could be a promising candidate for saturated blue-emitting polymers with spectral stability and high efficiency.

The peripheral triphenylamine-encapsulated red-emitting iridium(III) complexes have been designed and synthesized. External quantum efficiency over 15% has been realized in single-layer polymer light-emitting diodes, which is the highest ever reported for solution-processed red phosphorescence.

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