Research On HAC Solar Cell Technology

Heterojunction of amorphous silicon and crystalline silicon(HAC)solar cell is highly focused in high-efficiency solar cells since it possesses high open circuit voltage(VOC)and fewer process steps.Amorphous silicon(a-Si:H)passivation layer plays a key role in achieving high efficiency for HAC solar cells.However,the a-Si:H thin film with large absorption coefficient,low mobility,and parasitic absorption loss limits the short-circuit current density(JSC)of the solar cells.In this thesis,the deposition process of a-Si:H and ITO by hot-wire chemical vapor deposition(HWCVD)and DC physical vapor deposition(PVD)was studied;Then,HAC with diffused c-Si front surface field(HACD)solar cell is proposed in order to solve the parasitic absorption problem on the front side of the double-sided HAC solar cells.HACD cell deposition route is designed,and a full area HACD solar cell is prepared;Finally,a double-sided improved HAC with local pn structures(HACL)solar cell is proposed,and the HACL cells is simulated and analyzed using ATLAS software.The main findings are as follows:1.The a-Si:H sample deposited by HWCVD in this experiment has a maximum minority carrier lifetime higher than 5 ms.The vacuum breaking during the a-Si:H films deposition process would deteriorate the passivation effect;The structural defects introduced by high filament current deposited a-Si:H sample can't be eliminated during photothermal treatment.2.For ITO deposition,it is found that the thin film performances best when O2 in the gas sources accounts for 3.4%,and the bulk carrier concentration(Nb)of the thin film decreases as the O2 partial pressure increaseing.The relationship between carrier mobility(?)and Nb takes Nb=1×1020 cm-3 as the threshold,from positive to negative correlation.The introduction of H into the film can increase the transmittance and conductivity,but the conductivity caused by H will decrease after annealing.3.A full-area HACD solar cells with an efficiency of 18.2%is obtained.Compared with HIT cells,HACD cells have better short-wave light response,and Js,is 0.3 mA/cm2 higher.4.Simulation results show that HACL solar cells can maintain high VOC characteristics,and at the same time it can passivate electrode contact and solve the problem of a-Si:H parasitic absorption of HIT cells.JSC of the HACL solar cells is 4%higher than HIT solar cells simulated under the same conditions,and the potential conversion efficiency of 27.8%can be achieved.