14.13 % Efficient inkjet-printed kesterite solar cells enabled by selenium compensation through low-temperature selenium post-treatment

The inkjet-printed Cu2ZnSn(S,Se)4 (CZTSSe) has garnered extensive attention owing to its cost-effectiveness, high-throughput fabrication, and roll-to-roll compatibility. However, selenium volatility loss during high-temperature selenization induces detrimental defects in both bulk and interface, limiting CZTSSe solar cell performance. Here, we develop a simple and controllable low-temperature selenium post-treatment (Se-LPT) strategy to compensate for the selenium loss. Systematic studies reveal that the Se-LPT can effectively passivate selenium vacancy deep-level defects in the CZTSSe absorber and suppresses carrier nonradiative recombination, thereby reducing the open-circuit voltage deficit from 336 to 298 mV. Furthermore, this treatment lowers the carrier transport barrier and facilitates efficient carrier transport by reducing the spike-like conduction band offset at the heterojunction interface. The enhanced carrier density and conductivity further contribute to the short-circuit current improvement. Consequently, the Se-LPT CZTSSe devices deliver an efficiency of 14.13 %, representing the highest performance reported to date for inkjet-printed CZTSSe solar cells. This work demonstrates an effective route for developing cost-effective and high-efficiency CZTSSe photovoltaics.