Impact of intrinsic amorphous silicon bilayers in silicon heterojunction solar cells

Abstract

The impact of intrinsic amorphous silicon bilayers in amorphous silicon/crystalline silicon (a-Si:H/c-Si) heterojunction solar cells is investigated. The microstructure factor R* of the interfacial a-Si:H layer, which is related to the Si-H bond microstructure and determined by infrared absorption spectroscopy, is controlled in a wide range by varying the growth pressure and the power density in plasma-enhanced chemical vapor deposition process. Surface passivation at the a-Si:H/c-Si interface is significantly improved by using an intrinsic a-Si:H bilayer, i.e., a stack of an interfacial layer with a large R* and an additional dense layer, particularly after the deposition of an overlying p-type a-Si:H layer. Consequently, the conversion efficiency of a-Si:H/c-Si heterojunction solar cells is markedly increased. However, it is also revealed that such an interfacial layer causes some negative effects including the increase in the series resistance and the current loss at the front side, depending on the growth condition. This result indicates that the interfacial layer has a significant impact on both the majority and the minority carrier transport. Thus, R* of the interfacial layer is an important parameter for obtaining good surface passivation at the a-Si/c-Si interface, but not the sole parameter determining the conversion efficiency of a-Si:H/c-Si heterojunction solar cells.

Performance and Thermal Stability of an a-Si:H/TiOx/Yb Stack as an Electron-Selective Contact in Silicon Heterojunction Solar Cells

“…To investigate the contact structure in more detail, a TEM analysis was carried out on a textured sample with 1 nm TiO x before and after metallization (see Figures and ). As can be seen in Figure a,b, epitaxially grown crystallized a-Si:H at the c-Si/a-Si:H interface is shown because of a phase transition from crystalline to amorphous, which has been reported elsewhere. , This phenomenon could be mitigated by applying a porous a-Si:H layer on c-Si. , As for the TiO x , the thickness of the deposited TiO x layer corresponds to the nominal thickness of 1 nm, and the TiO x layer is closed while it conformally covers the i-a-Si:H surface. As shown in Figure c,d, the interfacial SiO x , formed as a result of the ALD TiO x process, can be found underneath both TTIP- and TDMAT-TiO x , although the thickness of this SiO x layer is slightly different in both cases.…”

Potential of very thin and high‐efficiency silicon heterojunction solar cells

“…H growth was applied in order to control passivation at the a-Si:H/c-Si interfaces, as reported in our previous work. 20 After the PECVD process, In 2 O 3 :Sn (ITO) films and Ag electrodes were formed on both sides of the piNin structures by means of magnetron sputtering with shadow masks, followed by thermal annealing at 160°C. Note that our ITO and front metal grid were not fully optimized, resulting in a relatively large shadow loss and series resistance compared with the state-of-the-art SHJ cells.…”

Integration of Si Heterojunction Solar Cells with III–V Solar Cells by the Pd Nanoparticle Array-Mediated “Smart Stack” Approach

“…One of the textured surfaces was flattened through chemical mechanical polishing processes to achieve a mirror-polished surface, which acts as the front (bonding) surface. After the wet cleaning process, intrinsic (i) and doped (n- or p-type) hydrogenated amorphous Si (a-Si:H) layers were deposited on both sides of the wafers using a plasma-enhanced chemical vapor deposition (PECVD) apparatus. − Here, we used the rear-emitter configuration with an i–p stack on the front side and an i–n stack on the rear side. In 2 O 3 /Sn (ITO) and Ag layers were further deposited on the rear side by sputtering to form a rear electrode.…”