Copper Oxide Buffer Layers by Pulsed‐Chemical Vapor Deposition for Semitransparent Perovskite Solar Cells

Abstract

In semitransparent perovskite solar cells with n–i–p configuration, thermal evaporation is the common method to deposit the sputter buffer material, such as molybdenum oxide and tungsten oxide. Buffer layers are especially necessary when using organic hole transporting layers, as they are more susceptible to get damaged when sputtering the top transparent conducting oxide. However, there is a limited selection of possible materials and limited control of the materials properties by thermal evaporation, which leads to inefficient protection against sputtering and poor air stability. While there have been well‐established buffer layers by atomic layer deposition, including tin oxide, for p–i–n structured semitransparent perovskite solar cells, this is not the case for n–i–p structured devices. Here, copper oxide is demonstrated by pulsed‐chemical vapor deposition incorporated into perovskite solar cells for the sputter buffer layer, which result in stable encapsulated semitransparent devices maintaining over 95% of the maximum efficiency under AM 1.5 G at maximum power point tracking for 150 h without any temperature control.

Inorganic Materials by Atomic Layer Deposition for Perovskite Solar Cells

“…Thus, there are approaches where the perovskite absorber is protected with various other layers to avoid direct exposure of the perovskite surface to the ALD processing conditions. To avoid direct exposure of ALD precursors to the perovskite active layer, an organic ETL, such as C 60 or [ 6 , 6 ]-phenyl C 61 butyric acid methyl ester (PCBM), or organic HTL, such as PTAA, are typically used as an interfacial layer to protect the perovskite from surface etching and/or bulk degradation [ 59 , 60 ]. Based on XRD analysis, approximately 50 nm of PTAA was sufficient enough to protect the underlying perovskite active layer from ALD processing damage, whereas direct CuO x deposition on top of the bare perovskite surface resulted in bulk degradation.…”

“…ALD copper oxide (CuO x ) and vanadium oxide (VO x ) have also been reported as buffer layers in semitransparent PSCs [ 72 , 73 ]. Growth methods by pulsed-chemical vapor deposition (pulsed-CVD) [ 60 ] or atmospheric-pressure chemical vapor deposition (AP-CVD) [ 64 ] have been reported for CuO x buffer layers in n - i - p structured semitransparent PSCs. CuO x films by AP-CVD resulted in high mobilities over 4 cm 2 /V·s, and semitransparent PSCs with these buffer layers resulted in PCEs over 16% ( Figure 7 c,d) [ 64 ].…”

“…Some common examples are pulsed-CVD [ 60 ], AP-CVD [ 64 ], and s-ALD [ 45 , 79 ]. Pulsed-CVD involves reducing the carrier purging step during the ALD sequence and pulsing the ALD precursors simultaneously, instead of separately, to reduce the deposition time [ 80 ].…”

Efficient and Stable Perovskite Solar Cells Based on Inorganic Hole Transport Materials

“…Copper oxides, such as cuprous oxide (Cu 2 O) and cupric oxide (CuO), are p -type semiconductors composed of environmentally friendly and abundant elements with low cost and suitable heat and ambient stability [ 71 ]. CuO has a bandgap of 1.3 eV and a valence band energy level of approximately −5.4 eV, while Cu 2 O has a bandgap of 2.1 eV, valence band energy level of −5.3 to −5.4 eV, and high carrier mobility of ~100 cm 2 /Vs [ 72 ].…”

Transparent Electrodes with Enhanced Infrared Transmittance for Semitransparent and Four-Terminal Tandem Perovskite Solar Cells

“…Inorganic–organic lead halide perovskites are ideal to be partnered with silicon in tandem configurations due to its low cost, simple solution processing capabilities, and high efficiencycertified as 25.5% in 2020 . Lead halide perovskites exhibit favorable absorber material properties, including large absorption coefficients and easy modification of band gap values via composition engineering, − making them an attractive top cell candidate in tandem configurations in conjunction with bottom cells of narrower band gap perovskite absorbers, along with chalcogenides and Sn-containing materials. − However, despite the many advantages of perovskite top cells in tandem configurations, widening the perovskite band gap through halide alloying, usually through increasing the Br content, leads to issues such as poor device stability from light-induced phase segregation and increased nonradiative recombination, which are issues that still need to be addressed. Perovskite–silicon tandem photovoltaic devices have been mainly demonstrated with either four-terminal or two-terminal tandem configurations, reported as 28.2 and 29.5%, respectively. ,,− …”