Metal Oxide Charge Transport Layers for Efficient and Stable Perovskite Solar Cells

Abstract

Currently, the efficiency of perovskite solar cells (PSCs) is ≈24%. For the fabrication of such high efficiency PSCs, it is necessary to use both electron and hole transport layers to effectively separate the charges generated by light absorption of the perovskite layer and selectively transfer the separated electrons and holes. In addition to the efficiency, the materials used for transporting charges must be resilient to light, heat, and moisture to ensure long-term stability of PSCs; furthermore, low-cost fabrication is required to form a charge transport layer at low temperatures by a solution process. For this purpose, metal oxides are best suited as charge transport materials for PSCs because of their advantages such as low cost, long-term stability, and high efficiency. In this Review, the metal oxide electron and hole transport materials used in PSCs are reviewed and preparation of these materials is summarized. Finally, the challenges and future research direction for metal oxide-based charge transport materials are described. 10% by using a submicrometer-thick mp-TiO 2 film and solid type hole transporting materials (HTM). [1a,16] We first reported an efficiency of 12% using an ≈400 nm thick mp-TiO 2 electrode and a polymeric HTM (poly-triarylamine, PTAA). [17] Subsequently, the thickness of mp-TiO 2 was reduced to less than 200 nm, and the efficiency was improved by over 22% by controlling the surface morphology, [4] composition, [18] and defect [19] of the perovskite optical absorber using the same PTAA.

High voltage vacuum-processed perovskite solar cells with organic semiconducting interlayers

“…6 Several studies have been focused on the understanding of charge transfer and interfacial processes between the perovskite, the ETLs, and the electrode, with the ultimate goal of maintaining a high charge collection efficiency and to abate non-radiative charge recombination. 7 Among ETLs, notable examples are n-type metal oxides, 8 in particular TiO 2 and SnO 2 , while the most widely adopted organic semiconductors are fullerene derivatives. 9 Fullerenes cannot only selectively transport electrons between the perovskite and the electrode, but are also capable to effectively passivate trap states and mitigate ionic migration at the perovskite surface and at the grain boundaries.…”

Efficient Vacuum Deposited P-I-N Perovskite Solar Cells by Front Contact Optimization

“…Perovskite solar cells (PSCs) are at the forefront of emerging photovoltaics materials, as demonstrated by the continuously rising power conversion efficiency (PCE) (Green et al, 2019). Achieving high conversion efficiencies requires placing the perovskite absorber in between selective charge transport layers that direct charge carriers to the appropriate electrodes for extraction (Pham et al, 2019;Shin et al, 2019). The choice of suitable charge selective materials depends on the type of device architecture used, the particular perovskite absorber, and on the thin-film processing technique.…”

“…While in some circumstances the direct ITO/HTL p-contact can lead to very efficient charge collection (Al-Ashouri et al, 2019;Liu et al, 2019), the interface is not ohmic, and an additional interlayer is usually placed in between the ITO and the HTL (Schloemer et al, 2019). Common interface materials are high work function molecules (Avila et al, 2018), doped organic semiconductors (Momblona et al, 2016;Schloemer et al, 2019), or metal oxides such as MoO 3 , V 2 O 5 , and W 2 O 3 (Shin et al, 2019). MoO 3 is widely adopted as it can be deposited in thin-films by simple thermal vacuum sublimation, resulting in quasiohmic interfaces (Schulz et al, 2016).…”

Metal Oxide Compact Electron Transport Layer Modification for Efficient and Stable Perovskite Solar Cells

“…The efficient TiO 2 CL/mp-TiO 2 nanopillar scaffold achieved fast carrier extraction and thereby suppressed recombination loss. Several other efficient mp-TiO 2 -based PSCs have also been reported to date [96,97]. properties because the lithium-doped mp-TiO2 lowered electronic trap states, which enabled faster electron transport.…”