Improving the performance of high-efficiency silicon heterojunction solar cells through low-temperature deposition of an i-a-Si:H anti-epitaxial buffer layer

In this work, an effective strategy for realizing high-performance silicon heterojunction (SHJ) solar cells involves replacing the existing rear single intrinsic hydrogenated amorphous silicon (i-a-Si:H) layer by depositing a bi-layer i-a-Si:H stack on the rear side using two different deposition chambers and manipulating the deposition temperature to inhibit epitaxial growth at the interface and maintain a good interfacial passivation effect. A low-temperature procedure is implemented to deposit the first anti-epitaxial i-a-Si:H buffer layer (I1 layer) of ∼1.5 nm thickness with a high hydrogen concentration and a low refractive index prior to the second bulk i-a-Si:H layer (I2 layer) of ∼5.5 nm thickness. The effects of the growth temperature and ignition power during deposition on the optical and structural properties of the i-a-Si:H buffer layers are investigated, and the impact of the buffer layers on carrier transport and collection is also evaluated. Utilizing this strategy, a trade-off between guaranteed passivation capability and low contact resistivity results in an improvement of 0.21%_abs in power conversion efficiency (PCE), which is mainly driven by increases in V_oc and FF, and a certified PCE of 25.92 %, with a high open circuit voltage (V_oc) of 749.7 mV, is achieved on a full-area M6-size industry-grade silicon wafer.