In Situ Grown Nanocrystalline Si Recombination Junction Layers for Efficient Perovskite–Si Monolithic Tandem Solar Cells: Toward a Simpler Multijunction Architecture

Abstract

The perovskite−Si tandem is an attractive avenue to attain greater power conversion efficiency (PCE) than their respective single-junction solar cells. However, such devices generally employ complex stacks with numerous deposition steps, which are rather unattractive from an industrial perspective. Here, we develop a simplified tandem architecture consisting of a perovskite n−i−p stack on a silicon heterojunction structure without applying the typically used indium−tin−oxide (ITO) recombination junction (RJ) layer between the top and bottom cells. It is demonstrated that an n-type hydrogenated nanocrystalline silicon (nc-Si:H) grown in situ on an amorphous silicon hole contact layer of the bottom cell acts as an efficient RJ layer, leading to a high opencircuit voltage (V OC ) of >1.8 V and a PCE of 21.4% without optimizing the optical design. Compared to the tandem cell with an ITO RJ layer, the nc-Si:H RJ layer not only improves light management but also achieves a higher V OC due to superior contact properties with an overlying SnO 2 electron transport layer of the perovskite top cell. Omitting the costly material and its deposition step offers the opportunity toward realizing industrially feasible high-efficiency tandem solar cells.

Nanoscale Size Control of Si Pyramid Texture for Perovskite/Si Tandem Solar Cells Enabling Solution‐Based Perovskite Top‐Cell Fabrication and Improved Si Bottom‐Cell Response

“…On top of the p ‐a‐Si:H hole contact layer, an n ‐nc‐Si:H recombination layer was grown in situ by plasma‐enhanced chemical vapor deposition (PECVD), enabling transparent conductive oxide (TCO)‐free interconnection between the top and bottom cells. [ 33 ] Then, the perovskite top cell was deposited in the n‐i‐p deposition sequence starting from tin oxide (SnO 2 ) (≈50 nm) as electron transport layer (ETL), perovskite as light absorber layer (500‐600 nm) and doped 2,2′,7,7′‐Tetrakis [N,N‐di(4‐methoxyphenyl)amino] −9,9′‐spirobifluorene (spiro‐MeOTAD) (≈200 nm) as hole transport layer (HTL). The bandgap of the perovskite absorber layer used in this study is ≈1.63 eV which provides reasonable current matching in the present tandem device design.…”

“…[41,42] In this study, phosphorous doped n-nc-Si:H was deposited as a recombination junction layer on top of the p-a-Si:H layer. [33] Prior to depositing n-nc-Si:H, a carbon dioxide (CO 2 ) plasma treatment was carried out on the underlying p-a-Si:H layer for 10 s to facilitate the nucleation of the nc-Si:H growth. [43] Then, ITO−Ag stacked layers were deposited on the rear side of the wafer without a mask by magnetron sputtering.…”

“…The details of our tandem device design and fabrication process can be found elsewhere. [33] Figure 3b shows the current density-voltage (J-V) curves of the perovskite/Si tandem cells with differently textured Si bottom cells. For comparison, a tandem cell with a front-planar rear-textured Si bottom cell was also prepared as a reference.…”

Overview and loss analysis of III–V single-junction and multi-junction solar cells

“…Although resistance loss is composed of absorber, interface, contact, interconnection and grid of solar cells, especially, fill factor of perovskite/Si tandem solar cells is dependent on contact resistance of interconnection of subcells such as transparent conductive oxide layer, recombination junction and so forth. Figure 9 shows correlation between fill factor and series resistance of perovskite singlejunction solar cell [28] and perovskite/Si 2-junction solar cell [29]. Calculated results for series resistance of perovskite single-junction solar cell were estimated by using equations ( 5)- (10).…”

Atomic Layer Deposited ZnO–SnO2 Electron Transport Bilayer for Wide‐Bandgap Perovskite Solar Cells

“…[15][16][17][18][19][20] Generally, surface passivation layers for silicon device were deposited by chemical vapor deposition or atomic layer deposition (ALD) (e.g., SiN x , Al 2 O 3 ), and the solutionproceed carrier transport layers exhibit poor surface passivation due to the lack of hydrogen or charges inside. [21] In addition, wide-bandgap perovskites that are suitable for high-efficiency tandem solar cells also suffer from a considerable V oc loss, [22][23][24][25] which can be attributed to the relatively low photoluminescence quantum yields (PLQY) of the perovskite itself and the unbefitting selection of carrier transport layer. [26] Many efforts have been made to boost the V oc , such as crystal modification, [27] surface passivation, [13] doping, [28] and perovskite composition engineering.…”