Kesterite Cu₂ZnSn(S,Se)₄ (CZTSSe) with earth‐abundant and environmental‐benign constituents has been regarded as a promising solar energy harvesting material for green and cost‐effective photovoltaic applications. The record efficiency of CZTSSe solar cells has recently been refreshed twice after years‐long stagnation, keeping it in the spotlight. Nevertheless, the champion efficiency of 13.6% is still far behind its counterpart Cu(In,Ga)Se₂ (CIGS) (23.35%) despite being endowed with a similar electronic structure and nearly‐identical device architecture. In fact, CZTSSe solar cells are more susceptible to non‐radiative recombination at bulk and interfaces, which must be improved for further efficiency advancement. In this review, the state‐of‐art strategies to enhance the power conversion efficiency of CZTSSe solar cells are summarized and discussed, with focus given to three critical device regions i) kesterite absorber, ii) buffer/kesterite interface, and iii) kesterite/back contact interface. With the further elucidation of the latest progress and disclosure of fundamental mechanisms, novel insights toward high‐efficiency kesterite solar cells are proposed.

Understanding carrier loss mechanisms at microscopic regions is imperative for the development of high-performance polycrystalline inorganic thin-film solar cells. Despite the progress achieved for kesterite, a promising environmentally benign and earth-abundant thin-film photovoltaic material, the microscopic carrier loss mechanisms and their impact on device performance remain largely unknown. Herein, we unveil these mechanisms in state-of-the-art Cu₂ZnSnSe₄ (CZTSe) solar cells using a framework that integrates multiple microscopic and macroscopic characterizations with three-dimensional device simulations. The results indicate the CZTSe films have a relatively long intragrain electron lifetime of 10–30 ns and small recombination losses through bandgap and/or electrostatic potential fluctuations. We identify that the effective minority carrier lifetime of CZTSe is dominated by a large grain boundary recombination velocity (~10⁴ cm s⁻¹), which is the major limiting factor of present device performance. These findings and the framework can greatly advance the research of kesterite and other emerging photovoltaic materials.

Cd-Free CZTS solar cell with above 10% efficiency was achieved by an Al₂O₃passivation layer prepared by ALD.

The rapid growth of the crystalline silicon (Si) photovoltaic industry has led to a steady increase in the production of waste silicon (wSi) generated during the cutting of Si ingots. Nevertheless, intrinsic oxidation and trace impurities in wSi make it difficult to retain or enhance its value for further use. Herein, we proposed a value-added recycling strategy to flash convert wSi into high performance amorphous Si nanowires (a-SiNWs). This method fully leverages the intrinsic oxidation properties of wSi and utilizes a high temperature gradient thermal field generated by carbon thermal shock to drive the directional diffusion of Si atoms within an oxide-limited domain environment. Copper nanoparticles are introduced to modulate the surface energy of Si atoms, inducing the formation of a-SiNWs. The a-SiNWs grow in situ on a carbon substrate, forming a self-supporting electrode material (identified as a-SiNWs@CC). The prepared a-SiNWs@CC is directly used as the anode of lithium-ion batteries, demonstrating excellent initial coulombic efficiency (ICE, 91.35%) and lithium storage capacity (up to 2150 mA h g⁻¹ at 2 A g⁻¹ for more than 250 cycles). The results hold great promise for the high-value utilization of wSi and the development of Si anodes.