Employing ZnS as a capping material for PbS quantum dots and bulk heterojunction solar cells

Abstract

Formation of bulk heterojunctions by incorporating colloidal quantum dots into a mesoporous substrate is anticipated to yield efficient charge collection and complete light absorption. However, it is still challenging in view of the bulky nature of the colloidal quantum dots and the ex situ deposition route. In this study, the feasibility of employing ZnS as a capping material for PbS quantum dots is dissected by carefully designed control experiments, with reference to the formation of bulk heterojunctions by successive ionic layer adsorption and reaction (SILAR) at ambient conditions. The results reveal that the underlying ZnS layer facilitates the PbS deposition by an ion exchange process, while the overlaying ZnS layer tends to cover the PbS in a manner similar to a physical stacking process. Therefore, PbS quantum dots capped with amorphous ZnS are developed with the SILAR technique, which could be used to fill up the mesoporous substrates and thus construct bulk heterojunctions. The hole collection is the limiting factor of such bulk heterojunction solar cells, as demonstrated by inserting a conductive polymer layer in the control devices. Further development of the quantum dot system is discussed in consideration of the fundamental issues presented in this study.

High-performance flexible and broadband photodetectors based on PbS quantum dots/ZnO nanoparticles heterostructure

“…Specifically, lead sulfide (PbS) QDs have been widely employed in photodetectors because of their inherent narrow bandgap (~1.3 eV) and tunable absorption spectra from the nearinfrared (NIR) to visible (Vis) [21,22]. So far, PbS QDs as essential photoactive layers have been utilized to construct different kinds of optoelectronic devices, such as p-n junction photodiodes, PIN photodetectors, and solar cells [23][24][25]. Compared with other semiconductors, ZnO with a room-temperature bandgap of 3.3 eV have attracted extensive attention owing to their easy fabrication process and photosensitivity for UV light detection.…”

Conformal Filling of TiO2 Nanotubes with Dense MxSy Films for 3D Heterojunctions: The Anion Effect

“…The annealed TiO 2 nanotubes were filled up with ZnS by SILAR method, as detailed in our previous reports ,. Briefly, the substrates were dipped into 0.1 M Zn(NO 3 ) 2 ⋅ 6H 2 O or Zn(CH 3 COO) 2 ⋅ 2H 2 O aqueous solution for 1 min, followed by rinsing with deionized water for another 1 min; and then dipped in 0.1 M Na 2 S ⋅ 9H 2 O aqueous solutions for 1 min, followed by rinsing with deionized water for another 1 min again.…”

Simple strategies deployed for developing efficient and stable solution processed quantum dot solar cells

“…, are coated, they passivate the trap states and favor charge injection into TiO 2 . 22,119–121 However, beyond an optimal thickness, they can hinder the process of hole-scavenging by the electrolyte in QDSCs.…”