Carbon polymer dots enhance stability and flexibility of near-2D perovskite photodetector

High-performance photodetectors with great detection ability have been widely deployed in our daily life, such as driverless technology, intraoperative navigation surgery, facial recognition, anti-counterfeiting and so on. However, we still face challenges as new demands arise for additional features such as extreme flexibility without loss of sensitivity/stability. Therefore, new photosensitive materials or multifunctional composites are needed to meet the rapid development of technology.

In a new paper published in Light: Science & Applicationsa team of scientists, led by Prof. Haotong Wei from the State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, China, developed a method of introducing carbonaceous polymer dots (CPDs) to promote the performance of quasi-2D perovskite based flexible photodetectors.

By controlling the morphology of the unique core/shell structure of CPDs with viscoelastic polymer chains, they greatly improved the flexible stability of perovskite photodetectors, with no loss of photoresponse after bending 10,000 times. In addition, the defects distributed at the perovskite grain boundary were passivated through the coordination effect between the unbonded Pb atoms and the carbonyl groups in the polymer chains of the CPDs.

The devices exhibited a lower dark current and resolved a weak light with the detectable light intensity dropping to 1/50, compared to the original performance. The reported method provides a cost-effective and available route to enhance the photodetection performance of flexible optoelectronic devices.

CPDs are composed of carbonaceous crystalline carbon as a core core in the center and covered by amorphous polymer chains as shells. The size of the carbon core can be easily controlled by adjusting the annealing temperature and time, and the polymer chains possess abundant functional groups, which bring tunable surface chemistry.

Therefore, the unique core–shell structure of CPDs ensures excellent viscoelasticity and tunable optoelectronic properties of CPDs. In addition, the raw materials of CPDs are abundant in nature, and the synthesis procedures are also easy and low-cost. Based on these considerations, these scientists proposed that perovskite/CPD composites may exhibit excellent photodetection performance and flexibility:

“We fabricated a series of CPDs with different morphological properties. By changing the temperature, the tailored carbonization process leads to various polymer chain lengths in the CPDs. And as we tuned the raw materials, these CPDs would bear abundant and controllable functional groups. to our requirements,” the researchers write.

“The different lengths of the CPDs provide a convenient way to control the flexibility of the devices. The elastic polymer chains of the CPDs would act as an anchor at the grain boundaries, making the perovskite morphology more stable during the deformation process. Furthermore, the abundant available raw materials of CPDs provide us with more options to tailor the properties of CPDs. The various functional groups carried by CPDs on the polymer chains coordinate with the Pb atoms to passivate grain boundary defects. functional groups, CPDs provide a path to tune the optoelectronic performance of the devices,” they added.

“Our method contributes to a new route to tailor the properties of optoelectronic materials and devices. By introducing these handy CPDs, we combine the properties of CPDs and perovskite materials and achieve high-performance photodetectors with great flexibility and stability. Our work it would inspire and advance flexible and foldable optoelectronic devices and promote their development and evolution.”