The efficiency of Cu₂ZnSnS₄ (CZTS) solar cells is limited due to interfacial band misalignment and severe non-radiative recombination. ZnSnO (ZTO) is a promising Cd-free buffer layer, offering a potential for favorable band alignment with CZTS absorber. Here, we demonstrate that optimizing the temperature-dependent deposition during reactive magnetron sputtering significantly promotes elemental interdiffusion. For the proposed CZTS/ZTO interface, a favorable “spike-like” band alignment is achieved, effectively enhancing the carrier transport efficiency and reducing the interfacial defect density. Furthermore, Zn diffusion mitigates Cu_Zn (that is, copper atoms sit at sites normally occupied by zinc atoms) antisite defects, reducing the non-radiative recombination and improving the absorber quality. Finally, the champion device achieved the highest power conversion efficiency (PCE) of 10.90% by sputtering ZTO as buffer layer in CZTS solar cell so far, with a high open circuit voltage (V_OC) of 740 mV and a fill factor (FF) of 61.79%. This strategy highlights the potential of sputtered ZTO as a scalable and eco-friendly buffer layer for Cd-free CZTS solar cells.

Introducing moderate iodide vacancies in halide perovskites has been frequently observed to form n-type doping effect and optimize the power conversion efficiency (PCE) of perovskite solar cells (PSCs). However, it has been widely recognized that iodide vacancies are mobile and photochemically detrimental. Herein, tris(2-aminoethyl)amine (TAEA), a branched molecule containing three primary amino groups and one tertiary amino group, is reported to passivate the undercoordinated Pb²⁺ ions and meanwhile n-dope the perovskite surface with its multiple amino groups. After TAEA post-treatment, the PSCs show robustly improved fill factor (FF) from 76.2% to 82.9%, improved open-circuit voltage (V_OC) from 1.08 to 1.16 V, and enhanced PCE from 19.4% to 23.4%. Moreover, the oxygen stability of the TAEA treated perovskite film has been substantially improved simultaneously, which is essentially different from the decreased oxygen stability in the case of using iodide vacancy as the n-dopant. Benefited from the iodide vacancies filling effect by TAEA, the activation energy (E_a) of ions migration in perovskites also increased from 0.43 to 0.67 eV.

Intensity, wavelength, and polarization are fundamental properties of light and typically represent the three detection dimensions in photodetectors. The information related to polarization includes additional subdimensions such as polarization state and phase difference, which can be resolved using crystals with birefringence. Inorganic materials exhibiting the electro-optic effect, like lithium niobate, are commonly employed in electro-optic modulation optical systems. However, their limited functionality poses challenges for integrating optical systems. Halide perovskites have been found to exhibit electro-optic effects due to symmetry loss in their crystal structures, making them promising candidates. These perovskites also serve as active materials with outstanding optoelectronic properties, providing opportunities for integrating electro-optically modulated polarization detection systems. This paper proposes a novel photodetector that utilizes electro-optic modulation of polarization response. The ultrafine nanoripples on the surface of the perovskite, along with micron-sized perovskite crystals, facilitate both polarization response and electro-optic modulation. This combination, enhanced by the exceptional optoelectronic characteristics of perovskites, enables the visualization of polarization modulation and the generation of multidimensional polarization currents, which can be leveraged for optical system integration and applications in machine learning.