A combined X-ray and scanning tunneling microscopy (STM) instrument is presented that enables the local detection of X-ray absorption on surfaces in a gas environment. To suppress the collection of ion currents generated in the gas phase, coaxially shielded STM tips were used. The conductive outer shield of the coaxial tips can be biased to deflect ions away from the tip core. When tunneling, the X-ray-induced current is separated from the regular, ‘topographic’ tunneling current using a novel high-speed separation scheme. We demonstrate the capabilities of the instrument by measuring the local X-ray-induced current on Au(1 1 1) in 800 mbar Ar.

We present a detailed material study of n⁺-type polysilicon (polySi) and its application as a carrier selective rear contact in a bifacial n-type solar cell comprising fire-through screen-printed metallization and 6" Cz wafers. The cells were manufactured with low-cost industrial process steps yielding V_ocs from 676 to 683 mV and J_scs above 39.4 mA/cm² indicating an efficiency potential of 22%. The aim of this study is to understand which material properties determine the performance of POCl₃-diffused (n-type) polySi-based passivating contacts and to find routes to improve its use for industrial PERPoly (Passivated Emitter Rear PolySi) cells from the point of view of throughput, performance, and bifacial application. This paper reports on correlations between the parameters used for low pressure chemical vapour deposition (LPCVD), annealing, and doping on optical, structural, and electronic properties of the polySi-based passivating contact and the subsequent influence on the solar cell parameters.