10.6% Certified Colloidal Quantum Dot Solar Cells via Solvent-Polarity-Engineered Halide Passivation

Abstract

Colloidal quantum dot (CQD) solar cells are solution-processed photovoltaics with broad spectral absorption tunability. Major advances in their efficiency have been made via improved CQD surface passivation and device architectures with enhanced charge carrier collection. Herein, we demonstrate a new strategy to improve further the passivation of CQDs starting from the solution phase. A cosolvent system is employed to tune the solvent polarity in order to achieve the solvation of methylammonium iodide (MAI) and the dispersion of hydrophobic PbS CQDs simultaneously in a homogeneous phase, otherwise not achieved in a single solvent. This process enables MAI to access the CQDs to confer improved passivation. This, in turn, allows for efficient charge extraction from a thicker photoactive layer device, leading to a certified solar cell power conversion efficiency of 10.6%, a new certified record in CQD photovoltaics.

Revealing Trap States in Lead Sulphide Colloidal Quantum Dots by Photoinduced Absorption Spectroscopy

“…Lead sulphide (PbS), in particular, attracts considerable interest due to its narrow bulk bandgap of 0.41 eV and the subsequent possibility to harness infrared photons in detectors and solar cells [1][2][3][4] or emit infrared light. [5][6][7] As-synthesized CQDs are commonly covered with long, electrically insulating surface ligands that need to be exchanged in order to promote electrical conduction.…”

Solution-Processed CdTe Thin-Film Solar Cells Using ZnSe Nanocrystal as a Buffer Layer

“…Solution-processed thin-film solar cells based on nanocrystals (NC), perovskites, or organic light absorbers have many merits such as low cost, easy large-area manufacturing, flexibility and high efficiency, which make them competitive when compared with traditional crystal Si or thin-film solar cells based on vacuum technics [1][2][3][4][5][6][7]. Among different kinds of NCs, CdTe NC solar cells have attracted greater attention in recent years [8][9][10][11].…”

Drastic difference between hole and electron injection through the gradient shell of CdxSeyZn1−xS1−y quantum dots

“…[1][2][3][4][5][6][7][8] Recently, Sargent and coworkers have achieved ∼11% solar power conversion efficiency using PbS/ZnO QDs via solvent-polarity-engineered halide passivation. 9,10 The long-term photo-stability of the QDs is a critical precondition for their photovoltaic applications. [11][12][13] By growing a wider band gap semiconductor shell around the core, these so called core-shell QDs (CSQDs) can be protected against possible surface traps and degradation.…”