SrTiO₃/Al₂O₃‐Graphene Electron Transport Layer for Highly Stable and Efficient Composites‐Based Perovskite Solar Cells with 20.6% Efficiency

Abstract

For practical use of perovskite solar cells (PSCs) the instability issues of devices, attributed to degradation of perovskite molecules by moisture, ions migration, and thermal‐ and light‐instability, have to be solved. Herein, highly efficient and stable PSCs based on perovskite/Ag‐reduced graphene oxide (Ag‐rGO) and mesoporous Al2O3/graphene (mp‐AG) composites are reported. The mp‐AG composite is conductive with one‐order of magnitude higher mobility than mp‐TiO2 and used for electron transport layer (ETL). Compared to the mp‐TiO2 ETL based cells, the champion device based on perovskite/Ag‐rGO and SrTiO3/mp‐AG composites shows overall a best performance (i.e., VOC = 1.057 V, JSC = 25.75 mA cm−2, fill factor (FF) = 75.63%, and power conversion efficiency (PCE) = 20.58%). More importantly, the champion device without encapsulation exhibits not only remarkable thermal‐ and photostability but also long‐term stability, retaining 97–99% of the initial values of photovoltaic parameters and sustaining ≈93% of initial PCE over 300 d under ambient conditions.

The role of carbon-based materials in enhancing the stability of perovskite solar cells

“…Recently, GR was applied in SrTiO 3 /Al 2 O 3 -GR ESL for stable and efficient PSCs based on LHP/Ag-RGO light absorber layer. 168 The encapsulated device exhibited notable thermaland photostability and retained 93% of the initial PCE over 300 d under ambient conditions. The enhancement in the longterm stability was due to the barrier effect of GR sheets, i.e., barrier to moisture penetration and ions migration.…”

Interfacial engineering with carbon–graphite–CuδNi1−δO for ambient-air stable composite-based hole-conductor-free perovskite solar cells

“…The strong chemical interactions and bonding between perovskite and Cu d Ni 1Àd O elements as well as the presence of C-G in composites also enhance the intrinsic stability of the perovskite materials and interfacial degradation. 16,[30][31][32]52 Moreover, the lattice constant of graphite (a ¼ 2.46 A) is less than the ionic diameter of I/Cl (d ¼ 4.28 A/3.62 A), which signicantly suppresses the halide migration towards the top electrode. In addition, the multistacked conguration of SnO 2 /Al 2…”

Advances in design engineering and merits of electron transporting layers in perovskite solar cells

“…109,110 For example, Feng et al deposited amorphous Nb 2 O 5 ETL for large-area rigid PSCs and flexible planar PSCs using an e-beam evaporation method, obtaining PCEs of 18.59% and 15.56%, respectively. 111 Moreover, other binary metal oxides, such as WOx 112,113 and In 2 O 3 , 114,115 and ternary metal oxides, such as Zn 2 SnO 4 , 116,117 BaSnO 3 118,119 and SrTiO 3 , 120,121 have been proposed for highefficiency PSCs as listed in Table 1. Based on eqn (2), the free electron concentration is dependent on the charge trapping-de-trapping process via defects in the metal oxide nanocrystals.…”