Design And Interface Optimization Of Fully Textured Monolithic Perovskite/Silicon Tandem Solar Cells

Owing to the outstanding device efficiency and stability,silicon solar cells have been dominating the photovoltaic industry.However,in recent years,the development of device efficiency in silicon solar cells has incurred a bottleneck due to the Shockley-Queisser limit.To tackle this issue,by stacking a wide-bandgap cell on the underlying narrow-gap silicon cell to form a tandem structure,photons in different solar spectrum bands can be more fully utilized,and the incident light energy loss of the silicon cell can be effectively reduced,thereby surpassing the efficiency limit of single-junction solar cells.The newly emerged perovskite solar cells have shown a rapid increment in power conversion efficiency.Meanwhile,perovskite solar cells also exhibit the advantages of tunable bandgaps and low-temperature processability,thus making them suitable for the wide-bandgap top cells combined with silicon devices.As the research on perovskite/silicon tandem solar cells continues to advance,compared with the commonly used float-zone-fabricated silicon wafers with polished surfaces or micro-textured structures,the Czochralski-process-textured silicon cells have the advantages of being compatible with industrial production lines while showing a significant light absorption,which is more conducive to the future development of the tandem solar cells.However,the Czochralski-process-textured silicon cells are incompatible with the mature perovskite solution process.The perovskite layer fabricated from a hybrid two-step deposition method combining sequential co-evaporation and spin-coating also has problems such as poor film quality and many interfacial defects.In this work,self-assembled molecular layer 2PACz with phosphoric-carbazole groups is introduced between the magnetron-sputtered NiO_x and the perovskite layer fabricated from a hybrid two-step deposition method combining sequential co-evaporation and spin-coating.2PACz anchors firmly at the interface,exhibits strong coordination with NiO_xand passivates the interface.Using this passivation mechanism,the introduction of 2PACz significantly improves the film quality of perovskite,with its efficacy being the improvement effects in the chemical polarity and flatness of NiO_x surface,which is conducive to the nucleation and crystal growth processes of perovskite films.Moreover,the interfacial passivation effect of 2PACz is analyzed quantitatively by the carrier dynamics model.Based on revealing the intrinsic mechanism of interface passivation by2PACz,this strategy realizes the optimization of the crystallization growth process of perovskite films.The high-quality perovskite film prepared with the 2PACz interfacial passivation strategy is further applied to the top cell of the textured perovskite/silicon tandem to improve its power conversion efficiency.NiO_x/2PACz as a hole transport layer significantly reduces the defect density of perovskite,enhances the hole extraction capability,and optimizes the interfacial energy-level matching.This strategy applies to perovskite solar cells with the 1.63 e V bandgap,and the top power conversion efficiency of the champion device reaches 20.5%.Most importantly,it is proved that 2PACz can still significantly improve the crystallization quality of perovskite films on textured silicon bottom cells.Under the condition of good current matching between the perovskite top cells and the silicon bottom cells,textured perovskite/silicon tandem devices successfully achieve the top power conversion efficiency of over 28%.This work proves that NiO_x/2PACz is an excellent choice for micro-textured perovskite/silicon tandem solar cells and promotes the development of synergistic applications of perovskite solar cells and silicon solar cells.