Xiaokang Zhou

A versatile hybrid polyphenylsilane host for highly efficient solution-processed blue and deep blue electrophosphorescence

A universal hybrid polymeric host (PCzSiPh) for blue and deep blue phosphors has been designed and synthesized by incorporating electron-donating carbazole as pendants on a polytetraphenylsilane main chain. The polymer PCzSiPh (4) has a wide bandgap and high triplet energy (ET) because of the tetrahedral geometry of the silicon atom in the tetraphenylsilane backbone. The distinct physical properties of good solubility, combined with high thermal and morphological stability give amorphous and homogenous PCzSiPh films by solution processing. As a result, using PCzSiPh as host with the guest iridium complex TMP-FIrpic gives blue phosphorescent organic light-emitting diodes (PhOLEDs) with overall performance which far exceeds that of a control device with poly(vinylcarbazole) (PVK) host. Notably, FIrpic-based devices exhibit a maximum external quantum efficiency (EQE) of 14.3% (29.3 cd A−1, 10.4 lm W−1) which are comparable to state-of-the-art literature data using polymer hosts for a blue dopant emitter. Moreover, the versatility of PCzSiPh extends to deep blue PhOLEDs using FIr6 and FCNIrpic as dopants, with high efficiencies of 11.3 cd A−1 and 8.6 cd A−1, respectively.

Deep ultraviolet-to-NIR broad spectral response organic photodetectors with large gain

We developed organic photodetectors with high photocurrent gain by enhancing the electron tunneling from the electrode owing to the effect of interface charge trapping. Furthermore, we utilized a down-conversion material to enhance the photoresponse in the deep-ultraviolet (UV) range. As a result, the photodetectors achieved an external quantum efficiency (EQE) of as high as 4000% while the photoresponsivity remained at 9 A W−1 at the UV wavelength of 250 nm. Finally, a high-performance organic photodetector with broad-photoresponse covering the spectral range from deep-UV (200 nm) to near-infrared (1000 nm) was successfully realized. The maximum EQE exceeds 10000% at a wavelength of 780 nm, and the photoresponsivity and specific detectivity are up to 70 A W−1 and 4 × 1012 Jones, respectively.

Vapour-assisted multi-functional perovskite thin films for solar cells and photodetectors

In this work, we manufactured high quality perovskite thin films via a vapour-assisted process. The film morphologies are qualified by XRD and SEM images. It can be seen that not only high efficiency solar cells, but also high detectivity photodetectors can be fabricated. The solar cells show a power conversion efficiency (PCE) of approximately 10% (with C60 as electron-transport layer). When PCBM serves as the electron-transport layer, the value exceeds 12%. In addition, the photodetectors also achieve a photodetectivity as high as 3 × 1012 Jones.

Side-chain engineering in naphthalenediimide-based n-type polymers for high-performance all-polymer photodetectors

A series of n-type semiconducting conjugated polymers based on naphthalene diimide (NDI) having three different side chains, 5-decylpentadecyl, 2-octyldodecyl and 4-(2-octyldodecyloxy)phenyl, were synthesized. Experimental results showed that the subtle structural changes at the side chains can influence the molecular packing, electron mobility, blend film morphology and thus performance of bulk-heterojunction polymer photodetectors using these NDI-based polymers as acceptors. The optimized all-polymer photodetector exhibited a specific detectivity (D*) of over 1013 Jones in the spectral region of 300–800 nm under −0.1 V bias, which is among the best D* values of the reported UV–vis–NIR all-polymer photodetectors and comparable to the best fullerene-based photodetectors.