In this study, we explore the photovoltaic performance of an innovative high efficiency heterostructure utilizing the quaternary semiconductor Cu₂FeSnSe₄ (CFTSe). This material features a kesterite symmetrical structure and is distinguished by its non-toxic nature and abundant presence in the earth’s crust. Utilizing the SCAPS simulator, we explore various electrical specifications such as short circuit current (J_sc), open circuit voltage (V_oc), the fill factor (FF), and power conversion efficiency (PCE) were explored at a large range of thicknesses, and the acceptor carrier concentration doping (N_A). Our results demonstrate that optimized parameters yield a remarkable PCE of 26.47%, accompanied by a V_oc of 1.194 V, J_sc of 35.37 mA/cm², and FF of 62.65% at a CFTSe absorber thickness of 0.5 μm. Furthermore, the performance of the photovoltaic cell is assessed for the defect levels in the CFTSe absorber and MoSe₂ buffer layers. Results indicate that deep defect levels above 1 × 10¹⁷ cm^− 3 lead to a decrease in J_sc. The study also investigates the effect of operating temperature on cell performance within the 300–500 K range. A notable decline in V_oc is observed, likely due to an increase in saturation current, suggesting an interaction between temperature and cell behavior. In this work, we propose a practical CFTSe-based structure that replaces conventional buffer layers, such as CdS, with MoSe₂ TMDC as a promising alternative buffer layer, paving the way for more sustainable solar technology.

Combined experimental and modeling studies of the magnetocaloric effect, ultrasound, and magnetostriction were performed on single-crystal samples of the spin-dimer system ${\mathrm{Sr}}_3{\mathrm{Cr}}_2{\mathrm{O}}_8$ in large magnetic fields to probe the spin-correlated regime in the proximity of the field-induced $XY$-type antiferromagnetic order also referred to as a Bose-Einstein condensate of magnons. The magnetocaloric effect, measured under adiabatic conditions, reveals details of the field-temperature $(H,T)$ phase diagram, a dome characterized by critical magnetic-fields $H_{c1}=30.4,H_{c2}=62\mathrm{T}$, and a single maximum ordering temperature $T_{\max }\left(45\mathrm{T}\right)\simeq 8\mathrm{K}$. The sample temperature was observed to drop significantly as the magnetic field is increased, even for initial temperatures above $T_{\max }$, indicating a significant magnetic entropy associated with the field-induced closure of the spin gap. The ultrasound and magnetostriction experiments probe the coupling between the lattice degrees of freedom and the magnetism in ${\mathrm{Sr}}_3{\mathrm{Cr}}_2{\mathrm{O}}_8$. Our experimental results are qualitatively reproduced by a minimalistic phenomenological model of the exchange striction by which sound waves renormalize the effective exchange couplings.