Synthesis and Optimization of Performance of Cu2ZnSnS4-based Nano-ink as Hole -Transfer Layer in Perovskite Solar Cells

In a perovskite solar cell, the photoactive layer is sandwiched between the electron and hole transfer layers (ETL and HTL). ETL and HTL play a very important role in photovoltaic performance. So far, record efficiency has been achieved using spiro-OMeTAD as HTL. But the high cost and complex synthesis process may limit its large-scale application. Inorganic semiconductors are a promising alternative due to their high mobility, stability, and the ability to synthesize and deposition by simple and inexpensive solution-based methods. In this study, a low-temperature carbon paste with Cu2ZnSnS4 (CZTS) nanomaterials were applied to transport and collect hole carriers. CuInS2 NPs were applied as the reference HTM. CZTS nanoparticles which are synthesized by heating-up method have a crystalline phase of wurtzite and a Zn-rich composition. The presence of the HTM layer at the perovskite/carbon interface has a significant effect on improving photovoltaic performance. The spin rate and number of HTM layers were investigated by spin-coating method. In the case of two-time deposition of nanomaterials, the maximum efficiencies of 12.61%, 13.38%, 10.74%, 11.40% were obtained for spin rates of 3000, 4000, 5000 and 6000 rpm, respectively. Increasing the number of HTM layers reduces the efficiency and current density. The spin rate of 4000 rpm and two-times deposition were obtained as optimal conditions. CIS-based device as a reference showed an efficiency of 15.5%. High performance compared to CZTS is affected by less defects and quality of perovskite surface coverage, which was confirmed by EIS, PL, VOC decay and AFM analyzes.