3D Branched Nanowire‐Coated Macroporous Titania Thin Films for Efficient Perovskite Solar Cells

• Published in: Advanced functional materials Vol. 28; no. 46
• Main Authors: Wu, Wu‐Qiang, Wang, Lianzhou
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 14.11.2018
• Subjects: charge collection; Charge transport; Collection; Design engineering; Energy conversion efficiency; Infiltration; light harvesting; macroporous metal oxide; Materials science; Nanowires; Optoelectronic devices; Perovskites; Photonics; Photovoltaic cells; Silicon dioxide; Sol-gel processes; Solar cells; Structural hierarchy; Thin films
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201804356

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. 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.