Selective emitter using a screen printed etch barrier in crystalline silicon solar cell

The low level doping of a selective emitter by etch back is an easy and low cost process to obtain a better blue response from a solar cell. This work suggests that the contact resistance of the selective emitter can be controlled by wet etching with the commercial acid barrier paste that is commonly applied in screen printing. Wet etching conditions such as acid barrier curing time, etchant concentration, and etching time have been optimized for the process, which is controllable as well as fast. The acid barrier formed by screen printing was etched with HF and HNO(3) (1:200) solution for 15 s, resulting in high sheet contact resistance of 90 Ω/sq. Doping concentrations of the electrode contact portion were 2 × 10(21) cm(−3) in the low sheet resistance (Rs) region and 7 × 10(19) cm(−3) in the high Rs region. Solar cells of 12.5 × 12.5 cm(2) in dimensions with a wet etch back selective emitter J(sc) of 37 mAcm(−2), open circuit voltage (V(oc)) of 638.3 mV and efficiency of 18.13% were fabricated. The result showed an improvement of about 13 mV on V(oc) compared to those of the reference solar cell fabricated with the reactive-ion etching back selective emitter and with J(sc) of 36.90 mAcm(−2), V(oc) of 625.7 mV, and efficiency of 17.60%.