Ternary CuZnS Nanocrystals: Synthesis, Characterization, and Interfacial Application in Perovskite Solar Cells

Abstract

Ternary CuZnS nanocrystals (NCs) are synthesized via a facile, scalable, noninjection method at low temperatures for the first time, wherein sodium ascorbate plays the dual roles of reducing agent and capping ligand in the preparation process. These NCs can be dispersed well in a polar solvent like dimethyl sulfoxide, and the average size is ∼4 nm as measured by transmission electron microscopy. The results of X-ray diffraction and X-ray photoelectron spectroscopy indicate that the crystal structure of CuZnS NCs displays covellite CuS-like structure and the Zn element partly occupies the Cu position. Also, the crystal structure of CuZnS NCs is completely converted from a covellite CuS structure into a digenite CuS structure when the NCs are treated above 350 °C. Moreover, CuZnS NCs demonstrate favorable hole transport properties. When it is employed in MAPbI-based perovskite solar cells as a hole transport layer, a peak power conversion efficiency of 18.3% is achieved. Simultaneously, the devices based on CuZnS exhibit a remarkably reduced J-V hysteresis. The results indicate that CuZnS is a promising hole transport layer for enhancing perovskite solar cell performance and presents great potential for optoelectronic applications, as well.

Raman and X-ray Photoemission Identification of Colloidal Metal Sulfides as Potential Secondary Phases in Nanocrystalline Cu2ZnSnS4 Photovoltaic Absorbers

“…There are different opinions regarding the structure of the Cu–Zn–S material, including ternary Cu–Zn sulfides, nonstoichiometric alloy semiconductor Cu x Zn y S, CuS–ZnS binary composites, Cu-alloyed ZnS, and Zn-doped CuS. 28–30 In ref , the spectrum of 3–7 nm NCs with Cu/Zn/S = 7:3:7 qualitatively coincides with that of CuS, with only the S–S mode shifted downward to 469 cm –1 . No effect of Zn content in the range from Cu/Zn = 1:14 up to Cu/Zn = 1:1 (!)…”

Fundamental Understanding of Photocurrent Hysteresis in Perovskite Solar Cells

“…[237] Very recently, ternary CuZnS nanocrystals synthesized via a facile method at low temperatures became another promising inorganic HTL material for PSCs, achieving a PCE of 18.3% and a remarkably reduced hysteresis. [238] In addition to these organic conductive polymers and inorganic p-type semiconductors, a new class of organic/inorganic hybrid molecules, the disodium salts of 2,3,6,7-tetraarylbenzo[1,2-b:4,5-b']dipyrrol-1,5-yl alkanediylsulfonates (BDPSOs), have become a promising HTL candidate to control the hysteresis and enhance the stability in PSCs. [239] In spite of their effectiveness in reducing hysteresis or enhancing stability, PSCs based on these inorganic HTL materials universally suffer from efficiencies lower than those based on conventional organic HTL materials.…”

Combinatorial Tuning of Structural and Optoelectronic Properties in Cu Zn1−S

“…We emphasize that remarkable properties and crystalline films have been achieved even at low deposition temperatures; this is particularly advantageous to applications in optoelectronic devices with low thermal budgets, such as CdTe and perovskite photovoltaics (PV). 30,31 Accordingly, Cu x Zn 1Àx S films of various crystallinity and microstructure have been recently demonstrated as, e.g., a transparent electrode in np + :Si PV devices with a demonstrated maximum open-circuit voltage of 535 mV, 22 a back contact on CdTe solar cells to enable bifacial PV, 32 a top contact on perovskite PV, 33 and a junction partner in self-powered UV photodetectors, 34,35 among other applications.…”