The article presents a strategic review of secondary phases, defects and defect-complexes in kesterite CZTSSe solar cells responsible for performance gap compared to CIGS solar cells.
Earth abundant Cu–Zn–Sn–S–Se (CZTSSe) is considered as a promising material for large area and cost effective solar energy harvesting. The current efficiency of CZTSSe champion solar cell, ∼12.7%, is much lower than that of its counterpart Cu–In–Ga–Se (CIGS) solar cell, ∼22.6%, and its theoretically predicted Shockley–Queisser (SQ) limit, ∼32%. This performance disparity is because of a large voltage deficit, ∼0.62 V, in comparison to the optical band gap that primarily results from high carrier recombination at the charge extraction interfaces. The different physical and chemical properties of interfacial layers often cause unfavorable band alignment and interfacial states that lead to high carrier recombination and eventually result in lower device efficiency. To obtain new insights about interfaces and to overcome the interface-related pitfalls, research on interface engineering of solar cells is rapidly accelerating and proven beneficial to achieve better device efficiency. This work provides a detailed strategic review on carrier transport and carrier recombination mechanisms by probing different interfaces of Mo/CZTSSe/CdS/i-ZnO/Al–ZnO/Al through every possible aspect. This review proposes eccentric approaches of carrier management.