One-Dimensional Electron Transport Layers for Perovskite Solar Cells

Abstract

The electron diffusion length (Ln) is smaller than the hole diffusion length (Lp) in many halide perovskite semiconductors meaning that the use of ordered one-dimensional (1D) structures such as nanowires (NWs) and nanotubes (NTs) as electron transport layers (ETLs) is a promising method of achieving high performance halide perovskite solar cells (HPSCs). ETLs consisting of oriented and aligned NWs and NTs offer the potential not merely for improved directional charge transport but also for the enhanced absorption of incoming light and thermodynamically efficient management of photogenerated carrier populations. The ordered architecture of NW/NT arrays affords superior infiltration of a deposited material making them ideal for use in HPSCs. Photoconversion efficiencies (PCEs) as high as 18% have been demonstrated for HPSCs using 1D ETLs. Despite the advantages of 1D ETLs, there are still challenges that need to be overcome to achieve even higher PCEs, such as better methods to eliminate or passivate surface traps, improved understanding of the hetero-interface and optimization of the morphology (i.e., length, diameter, and spacing of NWs/NTs). This review introduces the general considerations of ETLs for HPSCs, deposition techniques used, and the current research and challenges in the field of 1D ETLs for perovskite solar cells.

Halide perovskite solar cells using monocrystalline TiO2nanorod arrays as electron transport layers: impact of nanorod morphology

“…1D-ETLs also provide better pore filling of the perovskite absorber than the nanoparticulate structure in mesoscopic TiO 2 thin films because of their open pore structure [31][32][33].T i O 2 ,Z n O ,W O 3 , and CdS nanorods and nanotubes have been tested as ETLs for perovskite solar cells, but only TiO 2 nanorods (TNRs) have consistently produced HPSCs with PCEs above 15% [34][35][36][37]. Several works on the application of TNRs as ETLs have been documented [38].Q u i et al reported TNRs sensitized using an extra thin layer of CH 3 NH 3 PbBr 3 having a PCE of 4.87% [39].P a r ket al compared the photovoltaic performance of long (>1 μm) and short (<1 μm) TNRs, and found that the shorter nanorods provided better infiltration of perovskite. By using 560 nm long nanorods, they achieved a PCE of about 9.4% [33].J i a n get al tried to further optimize the length of nanowires for high performance HPSCs; they found that increasing the length of nanowires to 900 nm helped improving the PCE by enhancing the short-circuit current density, while increasing the nanowire length to 1.2 μm drastically reduced the short circuit current and open circuit voltage [40].…”

Vapor growth of binary and ternary phosphorus-based semiconductors into TiO2 nanotube arrays and application in visible light driven water splitting

“…have been used to demonstrate efficient Z-scheme CO 2 reduction photocatalysts, 40 high performance water photolyzers, 41 selective gas sensors, 42 and high efficiency solar cells. 43,44 Herein, we introduce TiO 2polyphosphide heterojunctions consisting of polyphosphide nanobers formed by the hitherto unexplored process of chemical vapor transport into TiO 2 nanotube array templates.…”

Graphene/Metal Oxide Nanocomposite Usage as Photoanode in Dye-Sensitized and Perovskite Solar Cells

“…Furthermore, they mostly contain toxic and rare elements, thus limiting their widespread applications [6,7]. To overcome these challenges, third-generation (3G) solution-processed solar cells have been developed, which include organic solar cells (OSCs), quantum dot-sensitized solar cells (QDSCs), dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs) [8]. Several PV technologies are under continuous development to meet the world demand for energy; in this chapter, however, we will focus our discussion in the emerging PV devices, i.e.…”

“…The discovery of organo metal halide perovskite CH 3 NH 3 PbX 3 (X = halogen) as highly efficient light absorber in both photoelectrochemical and photovoltaic cells shed new light on emerging cheaper and highly efficient next-generation solution processed solar cells [7,40]. Perovskite solar cells are a promising new substitute compared to silicon and dye-synthesized solar cells [2,8]. PSCs have become the most promising photovoltaic technology, due to their high efficiency (certified 22.1%) and low cost in less than 8 years of development [4,41,42].…”

“…ETL also acts as hole-blocking layer (HBL) [45]. The basic prerequisite for an ideal ETL is high conductivity, excellent electron mobility, high optical transmittance and an appropriate work function [8,44,46]. As far as PSCs are concerned, various ETLs such as TiO 2 , SnO 2 , Nb 2 O 5 , ZnO, Zn 2 SO 4 , In 2 S 3 and BaSnO 3 have been used successfully using different techniques [46].…”