High‐Performance Semitransparent and Bifacial Perovskite Solar Cells with MoO_x/Ag/WO_x as the Rear Transparent Electrode

Abstract

metal halide perovskites solar cells (PSC) have obtained significant progress with a conversion efficiency rising from 3.8% to 25.2%. [3,4] That outstanding conversion efficiency affords a large room to modulate the light transmittance for semitransparent devices. Moreover, the flexibility, neutral coloring, pleasing appearance, and low fabrication costs of PSCs enable their huge potential in the application of semitransparent solar cells. [5] To construct high-performance transparent PSCs with both high conversion efficiency and high transmittance, it needs both front and rear electrode layers in transparency. The instinct responsibility of front transparent electrodes (FTEs) film deposited on the front glass substrates is to allow the transmittance of solar light, [6-10] and is also more easily deposited in contrast to rear transparent electrodes (RTEs) because the latter films have to be deposited on the underlying perovskite absorber layer. Transparent conductive oxides (TCOs) like indium tin oxide (ITO) and fluorine doped tin oxide dominate FTEs in both photovoltaics and optoelectronics fields. [11] Unfortunately, classical TCOs can hardly be employed as RTEs because their depositions generally need high energy or high temperature, which may damage the underlying perovskite and carrier transport layers. [12] A strategy to overcome this problem is to develop alternative RTEs, such Semitransparent solar cells play a crucial role in such typical photovoltaic applications as smart windows, transparent chargeable devices, tandem and bifacial devices, and so on. Relying on the commercial conductive transparent oxides as the front electrodes, the development of rear transparent electrode (RTE) is especially essential. Here, an efficient semitransparent perovskite solar cell (PSC) with the softly deposited transparent MoO x /Ag/WO x (MAW) as the rear electrode is demonstrated. MoO x enables the continuously grown silver ultrathin film while the high-refractive-index WO x capping layer can modulate the whole optical interference and enhance the light transmission throughout the device. As a result, depending on the MAW RTE, the semitransparent normal planar PSC owns the optimal conversion efficiency of 15.40% along with 10.17% in the average visible-light transmission (AVT) simultaneously, which claims the best conversion efficiency of the semitransparent PSCs at such considerable AVT. Combining the optical characterizations, the bifacial performance test of the same device also reveals the uneven absorption due to the different optical interference depending on the light direction, as well as the typical parasitic absorption by the functional layers. This paper paves an alternative and promising way to fabricate high-performance semitransparent optoelectronic devices in the future.

Perovskite Solar Cells Go Bifacial—Mutual Benefits for Efficiency and Durability

“…To mitigate the parasitic light-absorption issues, TCOs with relatively high electron mobility and a low carrier density, such as hydrogen-doped indium oxide, [80,133] indium-doped zinc oxide, [133,134] and combined TCOs, [135] are employed as the rear electrode. Alternatively, some ultrathin metal/dielectric film stacks, [136][137][138] metallic nanostructures (e.g., Ag nanowires), [139,140] carbon nanostructures (e.g., graphene, nanotubes) [141][142][143] a have also been explored for metal-oxide-free transparent electrodes. However, their optical and electrical properties are still inferior to the TCO electrodes.…”

Halide Perovskite Solar Cells for Building Integrated Photovoltaics: Transforming Building Façades into Power Generators

“…With the “soft” evaporation process, PCE of 15.4% was demonstrated for ST‐PSC with 10.17% AVT. [ 86 ] The main disadvantages of DMD transparent electrodes are their relatively higher cost incurred from multiple thermal evaporation processes and the trade‐off in light transmission due to the highly absorptive nature of the metals.…”

“…Reproduced with permission. [ 86 ] Copyright 2020, Wiley‐VCH GmbH. c) Photograph of flexible ITO‐free semitransparent PSCs with a DMD multilayered electrode (b‐MoO 3 /Au/Ag/t‐MoO 3 /Alq 3 ).…”

“…b) Photographs and device structure of ST-PSC employing MoO 3 /Ag/WO 3 as top transparent electrode. Reproduced with permission [86]. Copyright 2020, Wiley-VCH GmbH.…”

Oxide/Halide/Oxide Architecture for High Performance Semi‐Transparent Perovskite Solar Cells

“…To date, various transparent electrodes such as indium tin oxide (ITO), indium zinc oxide (IZO), indium zinc tin oxide (IZTO), ultrathin metal layer, and oxide/metal/oxide (OMO) structure have been used to fabricate the top transparent electrodes (TTEs) of semitransparent PSCs through a vacuum or solution process. [17][18][19][20][21][22][23][24][25] Among the deposition processes, the transparent electrode fabricated by the solution process is not only chemically unstable but also not good in terms of reproducibility. [17,26] In contrast, the sputtering process is a mature large-area coating technology at present, and it is excellent in terms of chemical stability and reproducibility.…”