A low-temperature TiO2/SnO2 electron transport layer for high-performance planar perovskite solar cells

Abstract

Conventional titanium oxide (TiO 2) as an electron transport layer (ETL) in hybrid organic-inorganic perovskite solar cells (PSCs) requires a sintering process at a high temperature to crystalize, which is not suitable for flexible PSCs and tandem solar cells with their low-temperatureprocessed bottom cell. Here, we introduce a low-temperature solution method to deposit a TiO 2 /tin oxide (SnO 2) bilayer towards an efficient ETL. From the systematic measurements of optical and electronic properties, we demonstrate that the TiO 2 /SnO 2 ETL has an enhanced charge extraction ability and a suppressed carrier recombination at the ETL/perovskite interface, both of which are beneficial to photo-generated carrier separation and transport. As a result, PSCs with TiO 2 /SnO 2 bilayer ETLs present higher photovoltaic performance of the baseline cells compared with their TiO 2 and SnO 2 single-layer ETL counterparts. The champion PSC has a power conversion efficiency (PCE) of 19.11% with an open-circuit voltage (V oc) of 1.15 V, a short-circuit current density (J sc) of 22.77 mA cm −2 , and a fill factor (FF) of 72.38%. Additionally, due to the suitable band alignment of the TiO 2 /SnO 2 ETL in the device, a high V oc of 1.18 V is achieved. It has been proven that the TiO 2 /SnO 2 bilayer is a promising alternative ETL for high efficiency PSCs.

Preparation of Low Grain Boundary Perovskite Crystals with Excellent Performance: The Inhibition of Ammonium Iodide

“…Compared with the device before the NH 4 I treatment, solar cells treated with NH 4 I showed lower J 0 values and inflection points, suggesting a charging contact, which is more effective, for which the lower charging recombination and leakage at the interface between 3D-MAPbI 3 and TiO 2 -NAs should be responsible. 61 …”

Current advancements on charge selective contact interfacial layers and electrodes in flexible hybrid perovskite photovoltaics

“…To overcome these issues, surface modification using organic/inorganic/nanocarbon and ligand binding has been considered one of the proven techniques to passivate and modulate the optoelectronic properties of the contact interfaces (TiO 2 /perovskite layers). In this regard, the readers are advised to refer some of the recently published high-quality journal articles pertaining to the current status and developments of surface-modified TiO 2 [5,[66][67][68][69][70][71][72].…”

Photo-stable perovskite solar cells with reduced interfacial recombination losses using a CeOx interlayer

“…Thermal instability has been observed in ZnO-based PSCs and is attributed to the deprotonation of the organic cation caused by the basic nature of the ZnO surface [23]. Moreover, an enhanced charge extraction ability and suppressed carrier recombination at the TiO 2 /perovskite interface were also achieved using SnO 2 as the interlayer [24,25]. In addition to interfacial charge recombination, another issue associated with TiO 2 -based PSCs is the photo-induced device degradation [26].…”