Quantum Dots for Photovoltaics: A Tale of Two Materials

Abstract

solar cells (PSCs), and colloidal quantum dots (QDs) solar cells, have been quickly developed. [3][4][5][6][7][8][9][10][11] Among these diverse PV materials, QDs possess unique nanostructural uniformity and highly tunable features, including quantum confinement effects and multiple exciton generation (MEG). [12][13][14][15][16][17] QD solar cells can be fabricated as semitransparent and flexible for promising applications, such as, wearable energy collectors and building-integrated photovoltaics. [18,19] QDs are defined as nanometer-sized semiconducting crystals, usually chemically synthesized with surface ligands. [20,21] When the size of a semiconducting crystal reduces to the molecular scale, its bulk properties alter simultaneously. [22,23] Owing to the quantum confinement effect, the absorption spectra and energy levels of QDs can be easily tuned by size variation. For example, the bandgap of cadmium telluride (CdTe) bulk material is around 1.48 eV, while the bandgap of the CdTe QD can be tuned from 2.06 to 2.32 eV by a slight size reduction from 2.47 to 2.10 nm. [24,25] The quantum confinement effect also allows better energy level and absorption matching for QD-based optoelectronic devices such as photodetectors, light-emitting diodes, and solar cells. [26][27][28][29][30][31][32][33][34] Additionally, QDs enable hot cattier extraction due to the MEG effect, where one absorbed photon with high energy may generate two or more excitons. [27,35,36] The unique capability of MEG in QD solar cells can potentially improve the power conversion efficiency (PCE) of single-junction devices and thus overcome the Shockley-Queisser (SQ) PCE limit. [37][38][39] In the past decades, increasing research attention has been paid to QD solar cells, and many materials have been exploited in this context. Although there have been some trials on leadfree materials, such as Indium arsenide (InAs), InP, and AgBiS 2 , their device performances are still poor, with PCE less than 6%. [40][41][42][43][44][45] Up to now, most of the high-performance devices were reported from lead-based QDs in two main categories: lead chalcogenides (PbX, X = S, Se) and lead halide perovskites (PVK). Figure 1a depicts the progress in PCE values and accumulated publication numbers of lead-based QD solar cells, shown as points and columns, respectively, since 2010. With recent progress in device structure design, band-alignment engineering, and optimized surface passivation, the PCE of QD solar cells has constantly increased, achieving a record of 16.6% to date. [46][47][48] Before 2016, QD solar cells were mainly composed of PbX (X = S, Se), and continuous efforts have recently culminated in a remarkable PCE of 13.8%. [53][54][55] PbX usually crystallizes in a cubic structure with S or Se atoms located at octahedral Quantum dot (QD) solar cells, benefiting from unique quantum confinement effects and multiple exciton generation, have attracted great research attention in the past decades. Before 2016, research efforts were mainly devoted to solar cells ...

Recombination Dynamics in PbS Nanocrystal Quantum Dot Solar Cells Studied through Drift–Diffusion Simulations

“…While this work has been carried out for PbS NC solar cells, we hope the approach involving independent parameterization of drift–diffusion simulations will inspire analogous work on other NC solar cells. For example, parameterization and simulation of NC perovskite solar cells , could hopefully accelerate targeted development of techniques for NC preparation and assembly in devices. Size-dependent charge separation and recombination have been demonstrated, and optimization of NC preparation can improve carrier charge mobility and device efficiency .…”

A Solution‐Processed All‐Perovskite Memory with Dual‐Band Light Response and Tri‐Mode Operation

“…During the last decade, hybrid lead halide perovskites (CH 3 NH 3 PbX 3 , and X: I − , Br − , and Cl − ) have become prevalent because of their remarkable physical properties like ambipolar charge transport, [20,21] long diffusion length, [22] and low trapping density. [23] These characteristics make hybrid perovskites suitable for a broad range of devices, such as solar cells, [24][25][26][27] photodetectors, [28][29][30][31][32] light-emitting diodes, [33] lasers, [34,35] transistors, [36,37] and memories. [38][39][40] Compared with hybrid counterparts, all-inorganic halide perovskites (APbX 3 , A: Cs or Rb) have demonstrated better phase stability [41] and humidity stability.…”

CsPbI3 perovskite quantum dot solar cells: opportunities, progress and challenges

“…29 The distinguishing features of QDs include multi exciton generation (MEG) and the tuning of optical and electronic states via size reduction and quantum confinement effects. 30–32 MEG makes QDs exceptional among all the other PV materials, enabling the device to surpass the single-junction Shockley–Queisser (S–Q) limit of 33% PCE. 33 Traditional QDs (CdTe, CdS/Se, and PbS/Se) have been explored for the last thirty years and are well established in the light display market, while the emergence of halide perovskite QDs has paved a new avenue for solar-harvesting technology.…”