A Short Review on Interface Engineering of Perovskite Solar Cells: A Self‐Assembled Monolayer and Its Roles

the majority of the market shares as compared to next-generation thin-film PV technologies. Nevertheless, technological challenges in improving efficiencies and decreasing the high-energy requirements connected to the fabrication of silicon PV results in a higher global warming potential. In an effort to achieve lower fabrication cost and higher efficiencies, different types of thin-film PV technologies have been developed including dyesensitized solar cells, [2,3] organic solar cells, [4,5] copper indium tin sulfur [6,7] and emerging organic-inorganic lead halide perovskite solar cells (PSCs). [8,9] The combined merits of low fabrication cost and high power conversion efficiency (PCE) are distinct features of PSCs where PCE has jumped from 3.8% [8] to 25.2% [10] in just a decade. Such a sharp increase in PCE is mainly attributed to the large absorption coefficient, [11] long carrier lifetime, [12] high trap resistance, [13] high dielectric constant, [14-16] low binding energy, [17] and tunable bandgap of 1.2−1.7 eV, [18] all combined in a single perovskite material. 1.1. Perovskite Solar Cell Device Structures A typical perovskite solar cell consists of a light-absorbing perovskite layer which is sandwiched between an electron transport layer (ETL) and a hole transport layers (HTL). To complete the device, ETL is supported on a transparent conducting oxide (TCO) front electrode, and HTL on metal-coated back contact electrode, Figure 1. There are two basic structures for the PSC: the so-called mesoporous structure, which contains a mesoporous ETL layer (i.e., mesoporous TiO 2), and the planar structure, as depicted in Figure 1a,b. Even though early reports based on mesoporous devices assumed that the perovskite infiltration through the mesoporous scaffold improved the charge carrier collection to the electrode, later investigations performed by Lee and co-workers replaced the TiO 2 with an insulating Al 2 O 3 mesoporous layer, and reported for the first time the ambipolar nature of the perovskite materials, allowing the realization of longer diffusion length. [19] This enabled the fabrication of planar devices, and gave rise to an impressive evolution of device architectures, novel materials and cell configurations either in n-i-p or p-in designs. [12,19,20] In addition, Due to a certified 25.2% high efficiency, low cost, and easy fabrication; perovskite solar cells (PSCs) are the focus of interest among the nextgeneration photovoltaic technologies. Long-term stability is one of the most challenging obstacles to bring technology from the lab to the market. In this review, applications of self-assembled monolayers (SAMs) to enhance the power conversion efficiency (PCE) and stability of PSCs is discussed. In the first part, the introduction of SAMs, and deposition techniques applied to different PSC architectures are described. In the middle section, current efforts to utilize SAMs to fine-tune the optoelectronic properties to enhance the PCE and stability are detailed. The improvements in surface morphology, energ...

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Section: Deposition Techniques For Samsmentioning

confidence: 99%

Applications of Self‐Assembled Monolayers for Perovskite Solar Cells Interface Engineering to Address Efficiency and Stability

Ali

Roldán‐Carmona

Sohail

et al. 2020

Advanced Energy Materials

168

137

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“…To our knowledge, a couple of short or mini reviews have illustrated the progress on SAM‐introduced PSCs. [ 5 ] Despite these stimulating articles, the field has not yet benefited from a comprehensive review that highlights recent advances, discusses functions and mechanisms in depth, and provides future directions, with particular emphasis on SAMs for interfacial nanomaterials. This review describes recent studies that illustrate the benefits of applying SAMs to PSCs.…”

Section: Introductionmentioning

confidence: 99%

Self‐Assembled Monolayers as Interface Engineering Nanomaterials in Perovskite Solar Cells

Kim

Cho

Byeon

et al. 2020

Advanced Energy Materials

224

164

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process under mild conditions. The abovementioned advantages make perovskites a promising family of materials for the next-generation photovoltaic solar cells. Since the first report on the perovskite solar cell (PSC) by Miyasaka and coworkers in 2009, [1a] considerable efforts have been made to improve the power conversion efficiency (PCE) of the PSC to rival those of commercially available silicon solar panels. [1b-e] In a strikingly short period of time, the highest certified PCE has reached a value as high as 25.2% in a single-junction PSC. [2] Self-assembled monolayers (SAMs) are 2D nanomaterials with the thickness of one or few molecules. [3] Self-assembly of molecules on the surface is a thermodynamically favorable process where molecules interact with each other to form organized structures. Typically, molecules are vertically aligned on the surface with some tilt angle relative to the surface normal. The molecules are designed to have three parts: the anchoring, the spacer, and the terminal groups (Figure 1). 1) Anchoring group: the anchoring group is responsible for the interaction between the molecule and the surface. Various anchoring groups that bind to specific substrates are available, which provides users the option to select the type of electrode and molecule to suit their intended purpose. The most widely studied class of SAMs is derived from the anchoring chemistries between thiol and coinage metals or between silane and oxide substrates. In SAM-inserted PSCs, various oxide substrates are commonly used for bottom contacts, and few Brønsted-Lowry acids (e.g., carboxylic acid, phosphonic acid, and boronic acid) are extensively utilized (see below for details). Anchoring chemistry matters for the tilt angle of molecule with respect to the surface normal, work function (WF) of substrate, interfacial dipole, contact resistance, and energy offset between the Fermi level and energy of frontier molecular orbital. All of them are essential for the electronic function and performance of PSCs. These effects of SAMs on interfacial properties of PSCs are discussed below. 2) Spacer group: the spacer group is the backbone of the molecule, and it bridges terminal and anchoring groups. The length of the backbone is important for electronically isolating one contact from another. The spacer group is responsible for lateral interaction between molecules during the selfassembly process, which affects the final packing structure. Self-assembled monolayers (SAMs), owing to their unique and versatile abilities to manipulate chemical and physical interfacial properties, have emerged as powerful nanomaterials for improving the performance of perovskite solar cells (PSCs). Indeed, in the last six years, a collection of studies has shown that the application of SAMs to PSCs boosts the performance of devices compared to the pristine PSCs. This review describes recent studies that demonstrate the direct advantages of SAM-based interfacial engineering to power conversion efficiency (PCE) of PSCs. This review includes 1) a b...

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“…However, these issues can be overcome through interface engineering using photodiode architecture [40][41][42] that also greatly benefits from a vast knowledge base of highly performing rigid and ultraflexible perovskite solar cells. [43,44] X-ray detectors fabricated on a flexible substrate with photodiode architecture were reported by Gill et al, [45] achieving detection performance of 0.2 µC Gy −1 cm −2 at 0 V, though not accessing device flexibility.…”

Section: Introductionmentioning

confidence: 99%

Designing Ultraflexible Perovskite X‐Ray Detectors through Interface Engineering

et al. 2020

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X-ray detectors play a pivotal role in development and advancement of humankind, from far-reaching impact in medicine to furthering the ability to observe distant objects in outer space. While other electronics show the ability to adapt to flexible and lightweight formats, state-of-the-art X-ray detectors rely on materials requiring bulky and fragile configurations, severely limiting their applications. Lead halide perovskites is one of the most rapidly advancing novel materials with success in the field of semiconductor devices. Here, an ultraflexible, lightweight, and highly conformable passively operated thin film perovskite X-ray detector with a sensitivity as high as 9.3 ± 0.5 µC Gy −1 cm −2 at 0 V and a remarkably low limit of detection of 0.58 ± 0.05 Gy s −1 is presented. Various electron and hole transporting layers accessing their individual impact on the detector performance are evaluated. Moreover, it is shown that this ultrathin form-factor allows for fabrication of devices detecting X-rays equivalently from front and back side.

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A Short Review on Interface Engineering of Perovskite Solar Cells: A Self‐Assembled Monolayer and Its Roles

Cited by 92 publications

References 149 publications

Applications of Self‐Assembled Monolayers for Perovskite Solar Cells Interface Engineering to Address Efficiency and Stability

Applications of Self‐Assembled Monolayers for Perovskite Solar Cells Interface Engineering to Address Efficiency and Stability

Self‐Assembled Monolayers as Interface Engineering Nanomaterials in Perovskite Solar Cells

Designing Ultraflexible Perovskite X‐Ray Detectors through Interface Engineering

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