Review on ternary chalcogenides: Potential photoabsorbers

Abstract

The development of photovoltaic technology has brought in clean energy production. However, silicon is the most commonly used semiconductor in photovoltaics with power conversion efficiency (PCE) of about 18% to 22% under standard conditions. Recently, the chalcopyrite structure of I-III-VI2 constitutes ternary chalcogenides and the subsequent thin films are being used in second generation thin film solar cells (TFSC). Copper-based (Cu-III-VI2) and silver-based (Ag-III-VI2) chalcogenides are emerged as alternatives for toxic elements & lowcost in optoelectronics. In particular, Copper Indium Diselenide (with the optical band gap of 1.04 eV) cells have up to 14% efficiency with similar durability as silicon solar cells. Similarly, the optical band gap of Cu2SnS3 (CTS) thin films is 1.23 eV and the absorption coefficient is > 105 cm−1 and hence act as potential photoabsorber in TFSC. AgGaSe2 and AgGaTe2 have a direct band gap of 1.42 eV and 0.75 eV, respectively, and strong clarity in the 500–1200 nm wavelength range. Also, the optical properties of Ag-based chalcogenides (AgAlS2) are equivalent to those of Cu-based chalcogenides (CuAlS2). Similarly, a number of ternary semiconductors, including CuInS2, CuSnSe2, CuSbS2, AgInSe2, AgGaS2 and AgBiS2 with a bandgap in visible regions are created with rich crystal structures and high absorption coefficients using various deposition techniques, making them well suited for photoabsorbers. Herein, the latest progress of ternary chalcogenides is reviewed from the aspects of synthesis, characterization, and properties. In addition, their potential in optoelectronic devices is also discussed.