Strain-Induced Type II Band Alignment Control in CdSe Nanoplatelet/ZnS-Sensitized Solar Cells

Abstract

Colloidal CdSe nanoplatelets (NPLs) deposited on TiO 2 and overcoated by ZnS were explored as light absorbers in semiconductor-sensitized solar cells (SSSCs). Significant red shifts of both absorption and steady-state photoluminescence (PL) along with rapid PL quenching suggest a type II band alignment at the interface of the CdSe NPL and the ZnS barrier layer grown on the NPL layer, as confirmed by energy band measurements. The considerable red shift leads to enhanced spectral absorption coverage. Cell characterization shows an increased open-circuit voltage of 664 mV using a polysulfide electrolyte, which can be attributed to a photoinduced dipole effect created by the spatial charge separation across the nanoplatelet sensitizers. The observed short-circuit current density of 11.14 mA cm −2 approaches the maximal theoretical current density for this choice of absorber, yielding an internal quantum efficiency of close to 100%, a clear signature of excellent charge transport and collection yields. With their steep absorption onset and negligible inhomogeneous broadening, NPL-based SSSCs are intriguing candidates for future high-voltage sensitized cells.

Hybrid PbS Quantum‐Dot‐in‐Perovskite for High‐Efficiency Perovskite Solar Cell

“…As anticipated, MAPbI 3 –PbS QD hybrid films demonstrate a small increase of the absorption in the visible spectrum range, and an extended absorption to the near‐infrared to 900 nm compared to that of the pure MAPbI 3 film. The increased absorption in the near‐infrared is probably due to narrower bandgap of PbS QDs and the shift of the band‐edge due to the small strain at the QD–MAPI 3 interface . Some broadening of the optical response toward the red is also observed in the incident photon‐to‐current efficiency (IPCE) spectra in Figure B.…”

“…The increased absorption in the nearinfrared is probably due to narrower bandgap of PbS QDs and the shift of the bandedge due to the small strain at the QD-MAPI 3 interface. [32][33][34] Some broadening of the optical response toward the red is also observed in the incident photonto current efficiency (IPCE) spectra in Figure 3B. It can be seen that slight mismatch between integrated J in IPCE and J sc in J-V curves occurred.…”

Role of co-sensitization in dye-sensitized and quantum dot-sensitized solar cells

“…Addition of ZnS layer has already proven as effectively retarding the recombination process in QDSSCs [138]. By depositing the ZnS layer on the CdSe nanoplatelets layer, accumulation of holes in the valence band of ZnS raised the V oc of solar cell due to the formation of type-II band alignment [161]. Lee et al analysed the deposition of ZnS layer on the CdS/CdSe layer in TiO 2 photoelectrode.…”

Cadmium Chalcogenide Nano‐Heteroplatelets: Creating Advanced Nanostructured Materials by Shell Growth, Substitution, and Attachment

“…Nanoplatelets continue to reveal new unique features, such as narrow emission bands, very small Stokes shifts, and ultrafast charge carrier recombination . New possibilities for using these features in a wide range of practical applications are being reported . Meanwhile, in most cases, it is not the nanocrystals themselves that are used but various heterostructures based on them …”

“…[3] New possibilities for using these features in a wide range of practical applications are being reported. [4][5][6] Meanwhile, in most cases, The current direction in the evolution of 2D semiconductor nanocrystals involves the combination of metal and semiconductor components to form new nanoengineered materials called nano-heteroplatelets. This Review covers different heterostructure architectures that can be applied to cadmium chalcogenide nanoplatelets, including variously shaped shell, metal nanoparticle decoration, and doped and alloy systems.…”