A Brief Review of Transparent Conducting Oxides (TCO): The Influence of Different Deposition Techniques on the Efficiency of Solar Cells

Abstract

Global-warming-induced climate changes and socioeconomic issues increasingly stimulate reviews of renewable energy. Among energy-generation devices, solar cells are often considered as renewable sources of energy. Lately, transparent conducting oxides (TCOs) are playing a significant role as back/front contact electrodes in silicon heterojunction solar cells (SHJ SCs). In particular, the optimized Sn-doped In2O3 (ITO) has served as a capable TCO material to improve the efficiency of SHJ SCs, due to excellent physicochemical properties such as high transmittance, electrical conductivity, mobility, bandgap, and a low refractive index. The doped-ITO thin films had promising characteristics and helped in promoting the efficiency of SHJ SCs. Further, SHJ technology, together with an interdigitated back contact structure, achieved an outstanding efficiency of 26.7%. The present article discusses the deposition of TCO films by various techniques, parameters affecting TCO properties, characteristics of doped and undoped TCO materials, and their influence on SHJ SC efficiency, based on a review of ongoing research and development activities.

High Aspect Ratio Silver Nanogrids by Bottom-Up Electrochemical Growth as Transparent Electrode

“…Transparent electrodes (TEs) are critical components in numerous optoelectronic devices, such as displays, smart windows, touchscreens, (organic) light-emitting diodes (LEDs), and solar cells. − As technology advances, high-quality TEs are nowadays required to reduce the power consumption in efficient optoelectronic devices. In solar cells, high-quality TEs are essential to minimize power losses, particularly in cells with the top layer having a short carrier diffusion length, such as amorphous silicon, silicon heterojunction (SHJ), perovskite, copper indium gallium diselenide (CIGS), or organic cells. ,− In most commercial applications, metal oxides, indium tin oxide (ITO) in particular, have been most widely used due to their high transmittance, good conductivity, and complementary metal–oxide–semiconductor (CMOS)-compatible fabrication. , However, indium is a rare element that should be replaced, and after decades of optimization, ITO has reached its fundamental limits for transparency and sheet resistance, where the two are linked by the ITO thickness. , …”

Self-Diffusion versus Intentional Doping: Beneficial and Damaging Impact on Hematite Photoanode Interfaces

“…Antimony-doped tin oxide (ATO), indium tin oxide (ITO), and fluorine-doped tin oxide (FTO) are widely recognized as notable substrate examples commonly employed in most electrochemical applications including PEC systems. − From the available TCOs, FTO is frequently preferred over other options because of its superior thermal and chemical stability. This stability becomes particularly advantageous when high-temperature treatments are required. ,− Unlike ITO, which experiences a significant decrease in conductivity when exposed to temperatures above 350 °C, , FTO remains stable up to 800 °C. − Even at higher temperatures, FTO can maintain acceptable conductivities as long as the treatment duration is limited to less than 30 min. , …”

“…Because of the chemical conditions during operation, metallic platforms may not be the optimal choice as substrates for PEC applications. In contrast, glass-based transparent conductive oxides (TCOs) have emerged as an attractive and frequently preferred alternative due to their favorable balance between cost-effectiveness and performance. − These substrates offer high carrier concentration, excellent optical transparency exceeding 80% from 500 to 800 nm, and relatively lower cost compared with precious metals. Antimony-doped tin oxide (ATO), indium tin oxide (ITO), and fluorine-doped tin oxide (FTO) are widely recognized as notable substrate examples commonly employed in most electrochemical applications including PEC systems. − From the available TCOs, FTO is frequently preferred over other options because of its superior thermal and chemical stability.…”

Progress and Prospects with Cationic and Anionic Doping of Solution-Processed Kesterite Solar Absorbers: A Mini-Review

“…Then the TCO (ITO) layer acts as an antireflection coating at the front surface and also acts as an electrode to collect the charge carriers. 24 Kesterite absorbers were made by various physical and chemical synthesis routes. Also, there are several ways explored to improve the properties of these materials to achieve a good device.…”

“…In order to avoid front surface recombination, a window layer (ZnO) with a large bandgap is used. Then the TCO (ITO) layer acts as an antireflection coating at the front surface and also acts as an electrode to collect the charge carriers …”