Overcoming Charge Confinement in Perovskite Nanocrystal Solar Cells

Abstract

The small nanoparticle size and long‐chain ligands in colloidal metal halide perovskite quantum dots (PeQDs) cause charge confinement, which impedes exciton dissociation and carrier extraction in PeQD solar cells, so they have low short‐circuit current density Jsc, which impedes further increases in their power conversion efficiency (PCE). Here, a re‐assembling process (RP) is developed for perovskite nanocrystalline (PeNC) films made of colloidal perovskite nanocrystals to increase Jsc in PeNC solar cells. The RP of PeNC films increases their crystallite size and eliminates long‐chain ligands, and thereby overcomes the charge confinement in PeNC films. These changes facilitate exciton dissociation and increase carrier extraction in PeNC solar cells. By use of this method, the gradient‐bandgap PeNC solar cells achieve a Jsc = 19.30 mA cm−2 without compromising the photovoltage, and yield a high PCE of 16.46% with negligible hysteresis and good stability. This work provides a new strategy to process PeNC films and pave the way for high performance PeNC optoelectronic devices.

Assessing the Optoelectronic Performance of Halide Perovskite Quantum Dots with Identical Bandgaps: Composition Tuning Versus Quantum Confinement

“…Halide perovskite (ABX 3 ) quantum dots (QDs) have been extensively applied in high-performing optoelectronic devices such as photovoltaic cells, − light-emitting diodes (LEDs), − detectors, − lasers, − and so on. − One of the most attractive properties of perovskite QDs is their highly tunable optical characteristics, which are suitable for versatile applications. − The bandgaps of perovskite QDs can be readily and extensively tuned by controlling the compositions of A, B, and X sites. , Consequently, identical bandgaps can be achieved by various combinations of chemical components such as mixed cations, mixed halides, or their combinations . At the same time, the bandgaps of perovskites can be broadly adjusted by controlling their sizes through the quantum confinement effect. ,− For instance, perovskite CsPbI 3 bulk film has an intrinsically fixed bandgap of 1.70 eV, while the bandgaps of CsPbI 3 QDs can be flexibly modified from 2.13 to 1.73 eV by varying the size of the QDs. ,, …”

In Situ Ligand Compensation of Perovskite Quantum Dots for Efficient Light-Emitting Diodes

“…The 1D line cut of the corresponding GIWAXS pattern along the horizontal directions was extracted from the 2D-GIWAXS patterns (Figure f), which reveals that the diffraction peaks corresponding to the (010) and (110) lattice planes of cubic CsPbBr 3 perovskite were obtained, consistent with the XRD results. Moreover, both pristine and treated PQD-based solids turn out to stack along the in- and out-of-plane directions during the PQD solid film deposition, but the solid film prepared using the treated PQDs possesses more ordered arrangement evidenced by the more concentrated and intensive Bragg spots in the GIWAXS patterns . Meanwhile, the 2D-GISAXS patterns further verified the enhanced long-period periodicity in the treated PQD-based solids compared to the pristine samples, which exhibit more dispersive Bragg spots and looming diffraction rings for pristine PQDs (Figure S16).…”