Defect engineering of p‐type silicon heterojunction solar cells fabricated using commercial‐grade low‐lifetime silicon wafers

Abstract

In this work, we integrate defect engineering methods of gettering and hydrogenation into silicon heterojunction solar cells fabricated using low-lifetime commercial-grade p-type Czochralski-grown monocrystalline and high-performance multicrystalline wafers. We independently assess the impact of gettering on the removal of bulk impurities such as iron as well as the impact of hydrogenation on the passivation of grain boundaries and B-O defects. Furthermore, we report for the first time the susceptibility of heterojunction devices to light-and elevated temperature-induced degradation and investigate the onset of such degradation during device fabrication. Lastly, we demonstrate solar cells with independently verified 1-sun open-circuit voltages of 707 and 702 mV on monocrystalline and multicrystalline silicon wafers, respectively, with a starting bulk minority-carrier lifetime below 40 microseconds. These remarkably high opencircuit voltages reveal the potential of inexpensive low-lifetime p-type silicon wafers for making devices with efficiencies without needing to shift towards n-type substrates.

Sub-gap defect density characterization of molybdenum oxide: An annealing study for solar cell applications

“…The photovoltaic market is rapidly growing [1] and the crystalline silicon (c-Si) technology dominates the market [2]. As large-area industrial efficiencies have recently overcome the 24% mark [3] with passivated emitter rear cell (PERC) architecture and the 25% mark [4,5] with silicon heterojunction (SHJ) architecture, there is a demand for novel concepts and materials aimed at increasing further the power conversion efficiency. The SHJ architecture combines the advantages of thin-film silicon technology with a c-Si absorber to selectively collect the generated carriers.…”

Large‐Area Boron‐Doped 1.6 Ω cm p‐Type Czochralski Silicon Heterojunction Solar Cells with a Stable Open‐Circuit Voltage of 736 mV and Efficiency of 22.0%

“…It is important to note that with the addition of a dedicated gettering step to improve material quality, Descoeudres et al observed an efficiency gain of %0.2% abs in batches of p-type SHJ solar cells. [10] In previous studies, we have also demonstrated the role of gettering in increasing the lifetime of p-type Cz silicon, [5,11,12] which translated to a %1% abs increase in the efficiency of SHJ solar cells. These results together indicate the need for gettering as a defect-engineering process to enhance the quality of p-type silicon wafers for SHJ solar cells applications.…”

“…However, to date, little work has been done investigating LID in p-type SHJ solar cells. [11,20] For example, LID testing was not performed for the record cells from Descoeudres et al, although it was noted such wafers are likely to suffer from bulk degradation due to light-induced effects, [10] albeit with presumably a reduced total defect concentration due to the high wafer resistivity (6 Ω cm after gettering and the annihilation of thermal donors). In our recent work, we fabricated p-type SHJ solar cells that were susceptible to an efficiency degradation of 0.9% abs (4.7% rel ); [20] however, the degradation could be greatly reduced to 0.2% abs (1% rel ) using an advanced hydrogenation process.…”

“…After cell fabrication, the G and G þ H cells were separated into two groups: one group was the control, whereas the cells from the other group were treated with a modified UNSW advanced hydrogenation process (AHP) to mitigate BO-LID. [11] During AHP, excess carriers are generated via illumination to manipulate the hydrogen already existing in the solar cell. [22] No additional hydrogen source is provided during this process.…”

“…www.advancedsciencenews.com www.solar-rrl.com and holes at the a-Si:H/c-Si interface. [11,25] N-type SHJ solar cells can also be susceptible to this injection-level dependency of τ eff,low , and the problem can be solved by improving the passivation quality of the a-Si layer. [26] Thus, the optimization of the a-Si passivation layers could reduce the injection-level dependency of τ eff,low on p-type SHJ solar cells.…”