MoNo 2 cellThe MoNo 2 series n-type PV cell – an enhanced version of the MoNo 1 series – incorporates advanced features and improvements, says An. The MoNo 1 version, with 4 different wafer sizes, features a range of advanced technologies including stack wafer deposition process, emitter metal contact optimization, super thin fingers, and super multi busbars (SMBB).In the stacked wafer deposition process, when wafers are placed back-to-back or face-to-face, depending on the desired processing side, a slight wraparound layer forms on the opposite side. This can be removed with a single-side wet chemical etch. An also noted that the double-sided deposition process requires careful control of parameters, such as ramp rate and gas flow, as the wafers may experience thermal stress due to the asymmetric deposition of films. Additionally, optimizing the emitter metal contact allows a less corrosive metallization paste with fewer silver-aluminum (Ag-Al) spikes, reducing contact recombination. This results in an additional 5 mV in Voc and a 0.3% relative efficiency gain, without significantly affecting contact resistance, shared An.Moreover, improved metallization techniques, such as super-thin fingers (STF) and SMBB, which reduce grid spacing to enhance fill factor (FF), have been made possible by the development of silver paste that can be routinely printed with 20 µm narrow finger grid lines.Harnessing the key features of the MoNo 1 series, the company said it has enhanced the cell structure in the MoNo 2 series by incorporating multiple technological advancements – Super Thin Finger + (STF+), Half-Cut Edge Passivation (HEP), and Wave Back-Surface Field (W-BSF). STF+, a novel fine-line printing technique, pushes the limit down to 15 µm fingers with smaller spacing, reducing resistive losses in the metal and emitter while minimizing shading on the cell. According to JTPV, an increase in finger aspect ratio to up to 15% due to the STF+ metallization, leads to a gain of 0.3% FF and 0.1% efficiency compared to baseline cell with a finger aspect ratio of up to 55%. The company also noted that the incorporation of STF+ technology, along with adjusting the emitter sheet resistance to prioritize higher VOC over higher FF, can lead to a higher CTM value for module suppliers, without affecting efficiency gains. Furthermore, the improved finger aspect ratios enable a tradeoff between cell efficiency and silver paste consumption.
