Innovative Wide-Spectrum Mg and Ga-Codoped ZnO Transparent Conductive Films Grown via Reactive Plasma Deposition for Si Heterojunction Solar Cells

Abstract

In this work, wide-spectrum Mg and Ga-codoped ZnO (MGZO) transparent conductive films are developed via a reactive plasma deposition (RPD) technique with a soft thin-film growth process. MGZO film with a work function of ∼4.36 eV can be achieved within 12 min without any intentional substrate-heating treatment. The 480 nm-thickness MGZO film exhibits a low resistivity of ∼9.9 × 10–4 Ω cm and a high transmittance of ∼82.6% in the UV–vis–NIR region (λ approximately 400 nm–1200 nm). XRD spectra show that MGZO films exhibit (103) preferred orientation as the film thickness increases. A silicon heterojunction (SHJ) solar cell based on 480 nm-thick MGZO at the front side is completed. Excellent continuity of the MGZO film is proven by the cross-sectional SEM images, and there are no cracks and pinholes on the top or bottom of the c-Si pyramids. Further efficiency improvements are achieved using an ultrathin SnO x buffer layer with an ameliorated p-a-Si:H/TCO interface. Also, a silicon heterojunction (SHJ) solar cell using MGZO films on both sides is achieved with a conversion efficiency of 19.02%. These experimental results demonstrate that low-cost RPD-grown MGZO TCO materials could be commercially appropriate replacements for the conventional In2O3-based materials commonly used in SHJ solar cells and other optoelectronic devices.

Low-Temperature Oxide/Metal/Oxide Multilayer Films as Highly Transparent Conductive Electrodes for Optoelectronic Devices

“…Wide-spectrum MGZO transparent conductive films were developed via the RPD technique with a soft thin-film growth process in our previous research. 27 To obtain low-sheetresistance films, the thickness of the single MGZO layer should be at least 400−500 nm, where the transmittance line oscillates due to the interference phenomenon. For the RPD process, the thickness of the films is determined by the deposition time.…”

Broad-Spectrum Ultrathin-Metal-Based Oxide/Metal/Oxide Transparent Conductive Films for Optoelectronic Devices

“…To illustrate the potential application in broad-spectrum optoelectronic devices, the broad-spectrum OSCs with ultrathin Ag–Zn­(O)-based OMO electrodes are fabricated, and the device structure is shown in Figure a. In our previous research, the 480 nm-thick high-performance broad-spectrum MGZO-TCO thin films grown by RPD technology have been successfully applied to crystalline silicon heterojunction solar cells . For comparison, OSCs based on typical single-layer oxide (i.e., 480 nm MGZO) electrodes are also fabricated as the control group.…”

“…In our previous research, the 480 nm-thick high-performance broad-spectrum MGZO-TCO thin films grown by RPD technology have been successfully applied to crystalline silicon heterojunction solar cells. 10 For comparison, OSCs based on typical single-layer oxide (i.e., 480 nm MGZO) electrodes are also fabricated as the control group. The transmittance comparison of 480 nm MGZO and MGZO/Ag−Zn(O)/MGZO (50/5/50 nm) OMO thin films on glass substrates is given in Figure 6b.…”

“…For solar cells, the TCM transmits light to the absorption layer and collects photo-generated carriers. − Transparent conductive oxides (TCOs) with high transmittance and electrical conductivity have become a mainstream choice for TCM in solar cells. − However, high-performance TCO usually requires high-temperature deposition and/or post-annealing treatments. In addition, the strong ion bombardments in the TCO sputtering process are detrimental to the substrate or underlying layers and thus induce many defects. − Various TCMs have been explored at low temperatures to reduce the material cost of optoelectronic devices and flexible devices, such as carbon-based materials, − conductive polymers, − metallic nanostructures, − and ultrathin metal films. − …”

Transparent and flexible ZnO nanorods induced by thermal dissipation annealing without polymer substrate deformation for next-generation wearable devices

“…Among the various semiconductors, ZnO, a II-VI compound semiconductor with a wurtzite structure, is well suited for the fabrication of transparent and exible UV photodetectors, offering the benets of a wide direct bandgap (3.37 eV), large exciton binding energy (60 meV), high thermal stability, non-toxicity, and biocompatibility. [10][11][12][13][14] Moreover, ZnO exhibits the additional advantages of high electron mobility and high transparency in the visible region and it makes the ZnO to be applied in a various elds. [15][16][17][18] Compared to the common Sibased UV photodetectors, which require (i) complex lters to avoid noise due to the low electron energies and the narrow bandgap of Si and (ii) ultrahigh vacuum and high voltages for accurate detection, ZnO-based detectors can be used without lters for the reasons described above.…”