Near-infrared photodetection based on PbS colloidal quantum dots/organic hole conductor

We have developed Near-infrared (NIR)-sensitive heterojunction cells consisting of n-type PbS colloidal quantum dots (CQDs) (low bandgap) anchored on the nanoporous TiO2 (np-TiO2, high-bandgap), and p-type spiro-OMeTAD (2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene). In these cells, an n-type np-TiO2 layer acts both as a host that chemically binds to the PbS CQDs and as an electron carrier. The number of PbS CQDs loaded onto the np-TiO2 layer not only increases the external quantum efficiency (EQE) but also reduces the response time in the NIR region. The performance of these devices increased upon the introduction of a TiOx layer between the PbS CQDs and spiro-OMeTAD followed by heat treatment at 110 °C for 1 min.