NiOx hole transport layers enable industrial-scale, large-area heterojunction solar cells with efficiencies approaching 24%

Transparent passivated contacts (TPCs) have recently emerged as a promising strategy for enhancing the performance of silicon heterojunction (SHJ) solar cells, particularly with the development of efficient hole transport layers (HTLs). In this study, an optimized, a scalable NiO_x hole transport layer was successfully implemented on industrial-scale SHJ solar cells with an area of 220.5 cm² via electron beam physical vapor deposition (EB-PVD). A NiO_x HTL enables, a short-circuit current density (J_sc) of 40.06 mA/cm², but the open-circuit voltage (V_oc) was limited to 512 mV due to interfacial recombination. To address this, an ultra-thin p-type microcrystalline silicon (nc-Si:H(p⁺)) buffer layer with a thickness of 5 nm was inserted between the nc-Si:H(i) and NiO_x layers, forming an nc-Si:H(i)/nc-Si:H(p⁺)/NiO_x hetero-structure. This interfacial engineering strategy effectively suppressed carrier recombination, resulting in a substantial increase in the V_oc to 746 mV. The high passivation was accompanied by an enhancement carrier collection as seen by a fill factor of 81.96 %, thereby enabling a power conversion efficiency (PCE) of 23.89 % - among the highest for NiO_x-based SHJ solar cells. This study demonstrates the feasibility of integrating a novel dopant-free hole transport layer into industrial-scale, large-area silicon solar cells through rational interface engineering.