Flexible lead sulfide colloidal quantum dot photodetector using pencil graphite electrodes on paper substrates

Photoconductive photodetector fabricated from lead sulfide (PbS) colloidal quantum dots (CQDs) has demonstrated extremely high sensitivity and detectivity, in addition to their low-cost solution process. In this report we presented an extremely low-cost and flexible PbS photodetector using stone paper as the substrates and pencil drawn graphite as the electrodes. Single crystalline PbS CQDs and Au nanocrystals (NCs) with diameter of 3.2 nm and 7.5 nm were synthesized from the hot injection method. Layer-by-layer spin-coating was applied to construct the absorbing layer. By applying cetyltrimethylammonium bromide (CTAB) for the treatment and incorporating Au NCs into PbS CQD film, we have successfully built a fast and flexible device with detectivity up to 1.1 × 10¹⁰ Jones and 3 dB bandwidth of 61.2 Hz. Our flexible CQD photodetector might find its application in next generation flexible optoelectronic device.