Kang Chen

A template‐assisted solution‐processed technique is developed to fabricate 3D nanowire‐coated macroporous titania thin films with outstanding optical and electrical properties. Perovskite solar cells based on newly prepared TiO₂ electron‐transporting layer deliver an impressive power conversion efficiency of up to 20.1% owing to enhanced light harvesting and facilitated charge collection.

Abstract

Microscopic design and morphological engineering of the semiconducting metal oxide as electron‐transporting layers (ETLs) is of vital importance for optical enhancement, photonic structuring, and charge collection optimization within optoelectronic devices. Herein, nanowire‐coated, branched macroporous titania (BMT) thin films are reported as a new type of ETL prepared by using silica spheres as a sacrificial template, followed by a sol–gel and subsequent alkaline‐assisted etching process. The BMT films feature 3D hierarchical structures and interconnected networks with tunable pore sizes, branch densities, and film thicknesses. The titania films are employed as ETLs in perovskite solar cells (PSCs), resulting in remarkable power conversion efficiencies (PCEs) of 20.1%; a noticeable 16% increase compared with titania nanowire (TNW) ETL‐based counterparts (PCE = 17.3%). The superior device performance of the BMT‐based PSCs can be attributed to the maximized light harvesting and charge collection capabilities. These beneficial properties are derived from the effective infiltration of the perovskite precursor into the titania macropores, efficient light confinement within the macropore structure, and the textured perovskite capping layer, as well as enhanced charge transport and reduced charge recombination through the BMT architecture. This work demonstrates a simple and effective approach for constructing branched macroporous metal‐oxide photoelectrodes toward high‐performance photovoltaic devices.

High‐performance air‐stable perovskite solar cells are obtained after embedding carbon nanodots and urea into the perovskite. The best device performance features a power conversion efficiency of 20.2%, with negligible hysteresis. The devices displays excellent air‐stability for over 500 h without any encapsulation under 40% humidity (25 °C).

Abstract

Carbonized bamboo‐derived carbon nanodots (CNDs) as efficient additives for application in perovskite solar cells (PSCs) are reported. These carboxylic acid‐ and hydroxyl‐rich CNDs interact with the perovskite through hydrogen bonds and, thereby, promote the carriers' lifetimes and realize high‐performance p–i–n PSCs having the structure indium tin oxide/NiO _x /CH₃NH₃PbI₃ (MAPbI₃)/PC₆₁BM/BCP/Ag. As a result of interactions between the CNDs and the perovskite, the presence of the nonvolatile CND additive increases the power conversion efficiency (PCE) of the PSC from 14.48% ± 0.39% to 16.47% ± 0.26%. Furthermore, adding urea, a Lewis base, increases the PCE to 20.2%—the result of a significant increase in the crystal size and a lower content of grain boundary defects and, therefore, longer carrier lifetimes. Cells containing these two additives (without encapsulation) exhibit excellent shelf‐life and air‐stability, maintaining their high PCEs after storage in air—at a temperature of 25 °C and a humidity of 40%—for over 500 h. This performance is among of the best ever reported for p–i–n PSC devices incorporating carbon‐based additives.

In-situ cross-linking strategy for efficient and operationally stable methylammoniun lead iodide solar cells

In-situ cross-linking strategy for efficient and operationally stable methylammoniun lead iodide solar cells, Published online: 18 September 2018; doi:10.1038/s41467-018-06204-2

A fluorene-terminated hole-transporting material for highly efficient and stable perovskite solar cells

A fluorene-terminated hole-transporting material for highly efficient and stable perovskite solar cells, Published online: 09 July 2018; doi:10.1038/s41560-018-0200-6