Design and defect study of Cs2AgBiBr6 double perovskite solar cell using suitable charge transport layers

This work modelled and analysed perovskite solar cells based on Cs2AgBiBr6 with various electron transport layers and hole transport layers. The device structure is fluorine-doped tin oxide (FTO)/ZnO/Cs2AgBiBr6/NiO/Au. Power conversion efficiency (PCE) is practically saturated after the perovskite thickness of 700 nm. PCE declines from 21.88% to 1.58% when carrier lifetime decreases from 103 ns to 10−1 ns. Deep-level defects at mid-band gap energy of the perovskite layer can trap both carriers, allowing greater carrier recombination. Carrier capture cross-sectional area greatly impacts on cell performance. When subjected to high temperatures (T), the carrier mobility would diminish because carrier scattering increases cell resistance. That is why by raising T from 300 K to 400 K, the value of built-in potential (V bi) decreases from 1.17 V to 0.98 V. Device shows maximum efficiency when FTO is used as the front electrode, and Au is used as a back electrode. The optimum device, made of FTO/ZnO/Cs2AgBiBr6/NiO/Au, provides V oc = 1.29 V, J sc = 20.69 mA cm−2, fill factor = 81.72%, and PCE = 21.88%.