Improved efficiency of Cu(In,Ga)Se2 mini‐module via high‐mobility In2O3:W,H transparent conducting oxide layer

Abstract

AbstractPolycrystalline W and H codoped In2O3 (In2O3:W,H) transparent conducting oxide (TCO) layers with high electron mobility were found to enhance both the short‐circuit current density (Jsc) and fill factor (FF) of Cu(In,Ga)Se2 (CIGS) modules with glass/Mo/CIGS/CdS/ZnO/TCO structures. An In2O3:W,H TCO layer was formed by reactive plasma deposition without substrate heating, followed by postannealing at 150°C. A phase transition from amorphous to polycrystalline was confirmed during postannealing, and a layer with micrometer‐scale lateral grain sizes evenly covered the rough ZnO surface generated by the naturally textured CIGS. The crystallized In2O3:W,H film showed high electron mobility (apprixmately 80 cm2 V−1 s−1) at a carrier density of approximately 2 to 3 × 1020 cm−3. Therefore, the In2O3:W,H layer achieved lower sheet resistance and lower free carrier absorption than a ZnO:Al layer, which is commonly used in CIGS modules. The CIGS mini‐module employing the In2O3:W,H layer with a designated area of 3.792 cm2 exhibited a higher efficiency (η) of 20.93% (Voc = 3.081 V [translated value per subcell: 0.770 V], short‐circuit current = 33.21 mA [Jsc = 35.03 mA cm−2], FF = 0.775) with improved Jsc and FF, when compared with a mini‐module employing a ZnO:Al layer. The results indicate that polycrystalline In2O3‐based TCOs with high electron mobility are suitable for CIGS solar cells and modules.