High-Performance n-i-p-Type Perovskite Photodetectors Employing Graphene-Transparent Conductive Electrodes N-Type Doped with Amine Group Molecules

We first report high-performance n-i-p-type perovskite photodetectors (PDs) by employing n-type graphene (GR) transparent conductive electrodes (TCEs). The n-type GR is prepared by doping with ethylene diamine, diethylene triamine, and triethylene tetramine (TETA) containing two, three, and four amine groups, respectively. With increasing the number of amine groups (A_n) to four, the sheet resistance of the doped GR TCE is reduced to ∼205 ω/sq with only an ∼1% decrease of the transmittance at 550 nm while the work function is gradually enhanced to ∼4.46 eV, meaning n-type doping. The PDs optimized at A_n = 4 exhibit 10⁶ photocurrent/dark current ratio, 0.343 AW^-1 responsivity (R), 5.82 × 10⁹ cm Hz^1/2-W^-1 specific detectivity, 108 dB linear dynamic range, and 1.02 μs response time, comparable to the performances of the previously reported indium tin oxide-based perovskite PDs. In addition, flexible perovskite PDs with TFSA-doped GR TCEs show excellent bending stability, maintaining approximately 70% of the original R even after bending tests during 1000 cycles at a bending curvature of 4 mm.