Rapid‐Thermal‐Annealing‐Induced Passivation Degradation and Recovery of Polysilicon Passivated Contact with Czochralski and Cast Multicrystalline Silicon Substrates

Abstract

Carrier-selective passivating contacts as one of the most promising technologies for high-efficiency crystalline silicon (c-Si) solar cells (SCs) have been widely exploited for applications in heterojunction SCs, such as intrinsic thin hydrogenated amorphous silicon (a-Si:H) passivation layer (HIT) [1,2] and tunnel oxide passivated contact (TOPCon) SCs. [3][4][5][6] The remarkable advantages of a high open-circuit voltage (V oc ), a low-temperature coefficient, and a simple manufacturing procedure are usually endowed to HIT SCs. However, this type of HIT SC suffers from intrinsic drawbacks as well; for example, it is not compatible with the current mainstream passivated emitter and rear contact (PERC) technology, and it often requires capital-intensive equipment to produce the devices. In contrast, TOPCon technology has the potential to evade these issues, which thus has attracted significant attention in the global photovoltaic community. Apart from the advantage of the high compatibility with the PERC production lines, which could radically reduce manufacturing costs, an additional advantage of high potential efficiencies due to the excellent passivating contacts properties is also realized for TOPCon SCs. Remarkable progress in promoting the efficiency of this type of TOPCon device have been achieved, yielding a lab-scale record efficiency of 26.1%, [7] and a large-area industrial efficiency of 24.58%. [6] It is worthy noting that high-efficiency TOPCon SCs are usually produced using low-cost multicrystalline silicon (mc-Si) wafers, especially for the cast multicrystalline silicon (cast-mc-Si) wafers. [8] The key structures of TOPCon SCs are comprised of an ultrathin silicon oxide (SiO x ) layer and a highly doped polysilicon (poly-Si) layer. The SiO x layer can be deposited by various methods, such as wet chemical oxidation, [3,5,9] ozone oxidation, [10,11] thermal oxidation, [11,12] plasma assistant oxidation, [12,13] and atomic layer deposition (ALD). [14,15] A high-quality SiO x layer requires a suitable thickness to provide an excellent level of chemical passivation while allowing charge-carrier-selective