본 실험에서는 Cu2ZnSnS4(CZTS) 태양전지의 흡수층 상부에 다양한 조성을 갖는 Zn(Ox,S1-x) 버퍼층을 적용하여 특성 변화를 살펴보았다. Zn(O0.76,S0.24), Zn(O0.56, S0.44), Zn(O0.33,S0.67) 그리고 Zn(O0.17,S0.83)의 4가지 단일막의 경우, 전자-정공의 재결합 억제에 유리한 밴드갭 구조를 나타내는 Zn(O0.76,S0.24) 버퍼층을 소자에 적용했다. Zn(O0.76,S0.24) 버퍼층을 소자에 적용 시, 흡수층으로부터 S가 버퍼층으로 확산되어 소자 내에서의 버퍼층은 Zn(O0.7,S0.3)의 조성을 나타냈다. CdS 버퍼층의 EV보다 낮은 에너지 준위를 갖는 Zn(O0.7,S0.3) 버퍼층은 전자-정공 재결합을 효과적으로 억제하기 때문에 CZTS 태양전지의 JSC와 VOC 특성을 향상시켰다. 이를 통해 CdS 버퍼층이 적용된 CZTS 태양전지의 효율인 2.75%가 Zn(O0.7,S0.3) 버퍼층 적용을 통해 4.86%로 향상되었다.
This experiment investigated characteristic changes in a Cu2ZnSnS4(CZTS) solar cell by applying a Zn (Ox,S1-x) butter layer with various compositions on the upper side of the absorber layer. Among the four single layers such as Zn(O0.76,S0.24), Zn(O0.56, S0.44), Zn(O0.33,S0.67), and Zn(O0.17,S0.83), the Zn(O0.76,S0.24) buffer layer was applied to the device due to its bandgap structure for suppressing electron-hole recombination. In the application of the Zn(O0.76,S0.24) buffer layer to the device, the buffer layer in the device showed the composition of Zn(O0.7,S0.3) because S diffused into the buffer layer from the absorber layer. The Zn(O0.7,S0.3) buffer layer, having a lower energy level (EV) than a CdS buffer layer, improved the JSC and VOC characteristics of the CZTS solar cell because the Zn(O0.7,S0.3) buffer layer effectively suppressed electron-hole recombination. A substitution of the CdS buffer layer by the Zn(O0.7,S0.3) buffer layer improved the efficiency of the CZTS solar cell from 2.75% to 4.86%.
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