Electro-Deposited CuSCN Thin Films with Different Electrolyte Ratio for CuSCN/ZnO Self-Powered Photodetector Applications

This study basically evaluates the actual problem and solves that, CuSCN mobility is too low which eventually makes the ultimate response time as very slow. We fabricated p-n self-powered photodetector with zinc oxide (ZnO) and copper(I) thiocyanate (CuSCN) heterostructure with a different ion ratio of the electrolyte. We then found adjusting the ion ratio of the electrolyte which can increase the mobility of CuSCN and later improve the whole device efficiency. The best considerable performance tends to appear when the electrolyte ion ratio SCN: Cu (named as E_SCN/Cu) is 2. The intense responsivity is up to 27.29 mA W⁻¹ and the real response time is 6 s/12 s without any bias. We later found the energy barrier between ITO and CuSCN generally influences the responsivity. When E_SCN/Cu = 2, the valance band is near ITO, which eventually decreases the energy barrier. Compared with other published results, our device has the highest responsivity, which is anyhow caused by the bigger light absorbing area in ZnO nano-flower structure and the decay time faster than other devices is attributed to the Cu doping into ZnO which makes the mobility of ZnO increase and also reduce the vacancy which is filled by Cu and high mobility of CuSCN.