Alleviating performance and cost constraints in silicon heterojunction cells with HJT 2.0

Hole-Selective Front Contact Stack Enabling 24.1%-Efficient Silicon Heterojunction Solar Cells

“…Secondly, part of the optical benefits of the SiOx capping would be lost in an encapsulated module: the surrounding medium of the TCO on the light-incoming side has in that case a refractive index close to 1.5. A similar strategy was however shown industry-relevant by using an SiNx layer, which is less costly than the ITO layer and yield a 0.2% efficiency increase in industrial laboratory from optical benefit [35]. The electrical gains might be maintained in that case (although no FF improvement is reported in [35] using ITO and industry-optimized a-Si:H layers), and excellent antireflective performances could be reached by capping a relatively thin < 50-nm-thick IZrO film with an oxynitride layer (SiNxOy) which can provide a transparent layer with an optimal refractive index of 1.7.…”

“…A similar strategy was however shown industry-relevant by using an SiNx layer, which is less costly than the ITO layer and yield a 0.2% efficiency increase in industrial laboratory from optical benefit [35]. The electrical gains might be maintained in that case (although no FF improvement is reported in [35] using ITO and industry-optimized a-Si:H layers), and excellent antireflective performances could be reached by capping a relatively thin < 50-nm-thick IZrO film with an oxynitride layer (SiNxOy) which can provide a transparent layer with an optimal refractive index of 1.7. Then, the (p)nc-SiOx:H layer used in this study required four minutes of deposition, which is incompatible with cost-effective industrial throughput.…”

“…Another approach to minimize resistive and optical losses in the front TCO layer is to coat it with a SiOx:H film: such additional coating was shown to both improve the transmittance of light to the silicon wafer and reduce the sheet resistance of the TCO [33], [34]. A similar approach can be economically relevant for highvolume manufacturing [35], and increase the reliability of SHJ solar cells when combined to a tungsten-doped indium-oxide film [13]. The last building block used in the reported results is the application of a forward electrical bias to the finished solar cell.…”

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

“…In 2019, a number of groups demonstrated that SiN x /TCO composite layers at the front surface for rear-emitter SHJ solar cells can enhance the optical performance without damaging the lateral transport of carriers and the passivation. [93,97,98] In this architecture the parasitic absorption of the TCO can be reduced by designing a thinner TCO layer than the single-layer anti-reflective optimum (≈80 nm). In this case, a second anti-reflecting coating such as SiN has to be deposited on top of the TCO to minimize reflection losses.…”

“…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…”