The sputter deposition of broadband transparent and highly conductive cerium and hydrogen co‐doped indium oxide and its transfer to silicon heterojunction solar cells

Abstract

Indium oxide doped with tin (ITO) is the most commonly used material for lateral transport window layers in silicon heterojunction (SHJ) solar cells, as it currently offers the best combination of physical properties, industrial deposition capability, and module reliability. However, typically applied ITO layers by far do not exploit the full electro-optical potential of the indium oxide material class, resulting in optical and electrical losses limiting the solar cell efficiency. In this work, cerium and hydrogen co-doped indium oxide thin films are developed for their application as high-performance transparent conductive oxide layers in SHJ devices. Amorphous In 2 O 3 :Ce,H layers are fabricated via radio frequency magnetron sputtering, before being crystallized during post-deposition thermal treatments compatible with the SHJ temperature stability. The resulting excellent electro-optical film properties are on par with values so far solely reported for reactive plasma deposited films. It is shown that the surface morphology of the substrate (planar or textured) has a strong impact on the film properties, and further, the critical role of the atmosphere present during post-deposition annealing is elucidated. Finally, the large potential of an optimally processed In 2 O 3 :Ce,H window layer in SHJ cells is demonstrated, quantified by a gain in short circuit current density of 0.6 mA/cm 2 without impairing the resistive losses in comparison to the usage of a baseline ITO layer.

Atomic-layer-deposited Al-doped zinc oxide as a passivating conductive contacting layer for n+-doped surfaces in silicon solar cells

“…The degradation of the uncapped ZnO:Al layers most likely stems from interaction with air, as has also been observed for e.g. In 2 O 3 -based films [83]. The resistivity for the capped ZnO:Al layers gradually improves for annealing temperatures up to about 500 o C, followed by a further improvement for annealing at 550-650 o C. Overall, substantial reductions in the resistivity close to 50% can be obtained for the Al-doped samples.…”

Toward Efficiency Limits of Crystalline Silicon Solar Cells: Recent Progress in High‐Efficiency Silicon Heterojunction Solar Cells

“…By SPC processes, I 2 O 3 :H layers are first deposited at low temperatures (room temperature) in an amorphous matrix and subsequently annealed at temperatures ≈170 °C. Recently, high-mobility and thin NIR-transparent In 2 O 3 films have been produced by doping metals such as Cerium, [88,89] Titanium, [90] and Zirconium, [91] which perform as transparent electrodes for solar cells having sensitivity in the visible to the NIR wavelength region. [92] With higher carrier mobility (>100 cm 2 V −1 s −1 ), In 2 O 3 :Ce, In 2 O 3 :Ti, and In 2 O 3 :Zr are promising TCO candidates for SHJ solar cell production.…”

“…Approach for higher J SC Optimization of a-Si:H Wide bandgap carrier transport layers a-SiC:H, [70] a-SiO X :H, [71,73] nc-SiC:H, [72] nc-SiO X :H [75][76][77][78] Indirect bandgap carrier transport layers nc-Si:H [68,69] Optimization of TCO Higher mobility TCO layers I 2 O 3 :W, [84,85] I 2 O 3 :H, [86,87] In 2 O 3 :Ce, [88,89] In 2 O 3 :Ti, [90] In 2 O 3 :Zr [91] TCO/SiO x (SiN x ) composite layers a-SiO 2 /TCO, [93] SiO X /I 2 O 3 :W, [98] SiN/ITO [97] TCO-free SHJ Front TCO-free SHJ solar cells [96] Reduction of grid shadowing…”

Towards bifacial silicon heterojunction solar cells with reduced TCO use

“…Regarding the n-contact (or electron contact), the TCO/doped silicon junction is isotype, in which the transport of electrons is simple since it only occurs in the conduction band. From the left part of flow, and residual water in the chamber), 46 substrate morphology, 38,40,41 and the adjacent doped silicon layers 19,38 or dielectrical layer 47,48 in practical conditions. 49,50 For the p-contact (or hole contact), whose band diagram is shown in the right part of Figure 5A, the carrier transport is more complex than that in n-contact.…”