Jiahao Cheng,Wenlin Feng,Xiaozhan Yang,Cuicui Yang,Gang Zhang,Zhiying Liu
Bi 2 S 3 with a 2D van der Waals structure has attracted much attention due to its high conductivity, large absorption coefficient, and environmental friendliness. The preparation of tunable optoelectronic devices can be realized by exploiting and tuning Bi 2 S 3 intrinsic defects. In this work, a simple and rapid method for the preparation of bismuth sulfide thin films and successfully prepare Bi 2 S 3 with sulfur vacancies (S vac ) (LA-Bi 2 S 3 ) and oxygen passivated (S vac ) (AP-Bi 2 S 3 ) was presented. The defect state difference of the two devices leads to exhibit different optoelectronic properties. Under 638 nm and 1310 nm illuminations, the LA-Bi 2 S 3 photodetectors exhibit responsivities of up to 2250 and 3.6 mA/W and detectivities of 1.69 × 10 12 and 2.6 × 10 9 cm·Hz 1/2 W −1 , while the AP-Bi 2 S 3 photodetectors have ultra-fast on/off speeds of 1 ms and 8 ms, and on/off ratio up to 3 × 10 3 . The preparation method of the tunable optoelectronic devices gives a new avenue for defect tuning in metal sulfides and for the preparation and application of optoelectronic devices.
Interfaces quality have always been considered the key factors in the fabrication of efficient Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cells, and harmful defects at the interface can significantly reduce the performance of the device. Here, we propose a dual passivation strategy by adding Na to the surface of the absorber layer (CZTSSe) to passivate the CZTSSe/CdS interface and treating the buffer layer (CdS) using ultraviolet (UV) irradiation to passivate the CdS/ZnO interface. Due to the Na doping passivation, the absorber surface conductivity increases while the roughness decreases and detrimental defects that can lead to nonradiative recombination are reduced. The power conversion efficiency (PCE) of the cell is improved by about 1 percentage point by Na passivation. The contributions of open-circuit voltage ( V oc ), short-circuit current density ( J sc ), and fill factor (FF) to the improvement of PCE have been quantified as 50.64%, −5.58%, and 54.94%, indicating that Na doping can significantly boost V oc and FF. UV-ozone passivation reduces residual carbon organics in the CdS buffer layer , weakens carrier recombination, allows for more light absorption , and widens the depletion region , which favors efficient carrier collection. The estimated contribution of V oc , J sc , and FF to the PCE of the device is 8.78%, 119.59%, and −28.37%, respectively, demonstrating that UV-ozone passivation can significantly improve the J sc of the device. The two passivation strategies complement each other's advantages and achieve a synergistic effect . Our prepared champion device exhibits a PCE of 10.69% and remarkable long-term stability.
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