Synthesis of VS4 and VO on carbon nanofibers for back interface modification in HTL free CsPbBr3-based perovskite solar cells

Abstract

Carbon-based hole transport layer (HTL)-free all-inorganic perovskite solar cells (C-PSCs) exhibit advantages of simplified preparation procedure, high stability, and low cost, showcasing significant application potential. Nonetheless, the development of C-PSCs requires overcoming challenges such as the misalignment of energy levels between carbon counter electrode and the CsPbBr₃ perovskite, abundant defects at the perovskite/carbon back interface, and the carbon counter electrode's low conductivity. Herein, VS₄ and VO-deposited carbon nanofibers (CNF), termed VS₄@CNF and VO@CNF respectively, have been synthesized to adjust the work function and improve the conductivity of the carbon counter electrode. CsPbBr₃-based C-PSCs employing VS₄@CNF and VO@CNF as counter electrodes yield power conversion efficiencies of 7.88 % and 8.80 %, indicating great PCE enhancements of 15.4 % and 28.8 % as compared with the device with unmodified CNF counter electrodes. This improvement is attributed to the optimized conductivity and adjusted work function of the counter electrodes, which can optimize the energy level alignment, thereby enhancing charge carrier extraction and transport while effectively inhibiting recombination. Furthermore, VS₄@CNF and VO@CNF demonstrate a notable passivation effect on defects at the back interface. This study offers a valuable path for the design of novel carbon counter electrodes and the modification of the back interface in carbon-based all-inorganic C-PSCs.