Supersmooth Ta₂O₅/Ag/Polyetherimide Film as the Rear Transparent Electrode for High Performance Semitransparent Perovskite Solar Cells

Abstract

Semitransparent solar cells have attractedincreasing attention because of their gen eral applications in smart windows for automobiles and buildings, tandem solar cells, electronic chargers, and so on. [1][2][3] Due to facile solution processing and high record efficiency of 23.3% in nontrans parent devices, [4][5][6][7][8] organic-inorganic lead halide perovskite solar cells (PSCs) are excellent candidates for semitransparent devices, since the efficiency of semi transparent devices is inevitably lower compared to devices with fully reflective electrodes. In a typical semitransparent PSC structure, the rear transparent elec trode (RTE) is one of the key components because it is deposited on the underlying soft active layer. So far, various trans parent conductive electrodes have been investigated as RTEs for semitransparent PSCs, such as transparent conductive oxides, [9] conductive polymers, [10] carbon nanotubes, [11] graphene, [12] metal nano wires, [13,14] metal mesh, [15] ultrathin metal films, [16] and so on. Among them, the ultrathin metal films with the thickness below 10 nm have the advantage in the facile deposition pro cess, as well as low sheet resistance, high optical transmittance, and good adhesive strength comparable to other alternatives.The ultrathin silver film exhibits great potential as a low cost, effective RTE material in semitransparent devices. [17][18][19][20] However, there are still some challenges for the application of ultrathin silver films in high performance semitransparent PSCs. First, the 3D growth mode of silver results in separate islands for film thickness below 10 nm, [21] which leads not only low conductivity due to disconnect between parts of the electrode, [22] but also optical loss due to surface plasmonic effect. [23] The smooth and crossconnecting surface morphology of ultrathin silver film is necessary to realize high performance semitransparent PSCs. Second, the band level offset at the silver electrode interface always affects the carrier transport and collection, [24] especially for ultrathin silver electrodes. [25] The chemical interaction at the interface also determines the adhesive strength between silver film and the underlayer, as well as electrode degradation by halide anions and ambientAlthough it exhibits great potential as the rear transparent electrode (RTE) material in semitransparent devices, the ultrathin silver film still faces some significant challenges, such as surface plasmonic effect induced optical loss, the conflict between conductivity and transmittance, and the band level mismatch at device interfaces. In this work, a novel combination of ZrAcac/PEI/Ag/Ta 2 O 5 is employed as the RTE of the semitransparent perovskite solar cells in the planar inverted device structure of "indium-tin-oxide (ITO)/NiO x /MAPbI 3 /PC 61 BM/ZrAcac/PEI/Ag/Ta 2 O 5 ." Interface engineering with ZrAcac/PEI enables a significant increase in the device efficiency for 100 nm thick Ag electrode, from 17.48% to 18.84%. Ultrathin 9 nm Ag film coated on polyetherimide (PE...

Tantalum Oxide as an Efficient Alternative Electron Transporting Layer for Perovskite Solar Cells

“…Ta 2 O 5 -ZnO composite film has been used as a cathodic buffer layer for inverted polymer solar cells to get enhanced efficiency [ 39 ]. In an interesting work by Ying et al, a combination of ZrAcac/PEI/Ag/Ta 2 O 5 was employed as the rear transparent electrode of semi-transparent PSCs, leading to enhanced transmittance [ 40 ]. It is suggested that materials with high dielectric constants could offer better charge separation and improve the photovoltaic efficiency by suppressing the carrier recombination across the interfaces [ 41 , 42 , 43 ].…”

High‐Performance Semi‐Transparent Organic Photovoltaic Devices via Improving Absorbing Selectivity

“…The use of PEI as wetting layer has been reported to induce smooth growth of Ag film. [47,49] While, the ZnO NP serves to facilitate charge collection. As shown in Figure 3c,d, the PEI modification induces smoother film, and significantly decreases the surface roughness from 3.13 to 1.67 nm, compared to that with PFN-Br.…”

“…[19] A branched polyethylenimine (PEI) layer is deposited on top of ZnO nanoparticles (NP) layer to reduce the granule size of ultra-thin Ag transparent electrode. [47][48][49] The resultant smooth ultra-thin Ag film effectively alleviates light scattering and improves the absorbing selectivity of ST-OPV. Further, with the guidance of optical simulation, an optical interference layer, that is, TeO 2 , is deposited on top of the ultra-thin Ag layer, and this dramatically improves absorbing selectivity via increasing the transmittance in visible region without significantly sacrificing absorption in invisible region.…”

Recent Progress on Advanced Optical Structures for Emerging Photovoltaics and Photodetectors

“…The DMD structures in ST‐PSCs have been similar to those in ST‐OPVs. [ 33,45,48,49,73,74,78,79,117–122 ] For example, Hanmandlu et al introduced a 2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline (BCP)/Ag/MoO 3 transparent electrode for bifacial PSCs (Figure 2d). [ 79 ] In addition to providing a high dielectric constant, the BCP also functioned as a diffusion buffer layer between the electron transport layer (ETL) and the Ag electrode.…”