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We demonstrate a bifaciality of 88.0% for 6-inch bifacial p-type Cz-Si passivated emitter and rear cells (biPERC) and increase their rear side energy conversion efficiency to 18.0% by minor adaptions in the fabrication sequence. We utilize the “pPassDop” concept on the cells’ rear side that applies an aluminum oxide and a boron-doped silicon nitride (SiN X :B layer stack for simultaneous passivation and doping source. Laser doping forms the local p-doped back surface field regions for these biPERL solar cells. Screen-printed silver-aluminum metallization contacts these regions. We also demonstrate the compatibility of the laser doping approach with conventional (undoped) SiN X capping layer to fabricate biPERL devices with screen-printed contacts.

We present an approach to analyze and identify the predominant loss mechanisms in silicon solar cells. For this end, all losses are converted to potential efficiency gains and are thus directly comparable to one another as a derivative-like quantity. This derivative-like nature of the gains is validated at the hands of numerical simulations, showing that the formulary of the method basically calculates the derivatives of the efficiency with regard to the input parameters. The approach is solely based on measured data alone and recombination currents are measured at maximum power point like conditions. It is the first method to combine all these characteristics and is exemplarily applied to passivity emitter and rear cells (PERC) based on $p$-type mono- and multicrystalline silicon wafers. For our examined solar cells, we identify as bottlenecks the optical and recombination properties of the front side metallization in case of the monocrystalline PERC cell and the reflection at the active area in the multicrystalline case with potential efficiency gains of $1.2\%_{\mathrm {a}\mathrm {b}\mathrm {s}}$ and $1.6\%_{\mathrm {a}\mathrm {b}\mathrm {s}}$, respectively.

We investigate the role of a few nm thin thermal oxide films in PECVD passivation layer systems. Our results show that an intermediate thermal oxide layer located between the Si substrate and the PECVD layers has a strong impact on the interface properties. Capacitance-voltage measurements reveal that for Al 2 O 3 and SiN X passivation layers, the oxide film lowers or suppresses the formation of fixed charges. Adjusting the oxide film thickness therefore permits the control of band bending and thus field effect passivation at the interface. For SiO X capping layers, a thermal oxide thickness of a few nm is sufficient to reduce the interface trap density, enabling surface recombination velocities as low as a few cm/s.

Recently we reported the possibility of using the room temperature plasma oxidation mechanism to obtain ultrathin silicon oxide films. The oxidation process in O2 and N2O can be modeled by power law dependence with time and is inversely proportional with pressure. On that work, the parameters that modeled the oxidation process were fitting parameters and were analyzed independently for each gas. In present work we derived a general expression to model plasma oxidation processes. In addition, the dependence of the oxidation rate with pressure and temperature were further specified so they are associated to physical mechanisms. Comparison of experimental curves with modeled, using this general expression, is presented.