Low temperature deposition of high open-circuit voltage (>1.0 V) p-i-n type amorphous silicon solar cells

P-i-n type hydrogenated amorphous silicon (a-Si:H) solar cells were deposited by the radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) process at a low substrate temperature of 125 °C, which is compatible with low-cost poly (ethylene terephthalate) (PET) plastic substrates. Wide band gap (E_opt>1.88 eV) intrinsic a-Si:H films were achieved before the onset of the microcrystalline regime by changing the hydrogen dilution ratios. On the other hand, the structural, optical and electrical properties of p-type hydrogenated amorphous silicon carbide (p-a-SiC:H) window layers have been optimized at 125 °C. High quality p-a-SiC:H film with high optical band gap (E₀₄=2.02 eV) and high conductivity (σ_d=1.0×10⁻⁷ S/cm) was deposited at ‘low-power regime’ under low silane flow rates and high H₂ dilution conditions. With the combination of wide band gap p-a-SiC:H window layers and intrinsic a-Si:H layers, a high V_oc of 1.01 V (efficiency=5.51%, FF=0.72, J_sc=7.58 mA/cm²) was obtained for single junction a-Si:H p-i-n solar cell at a low temperature of 125 °C. Finally, flexible a-Si:H solar cell on PET substrate with efficiency of 4.60% (V_oc=0.98 V, FF=0.69, J_sc=6.82 mA/cm²) was obtained.