A New Dioxasilepine-Aryldiamine Hybrid Electron-Blocking Material for Wide Linear Dynamic Range and Fast Response...

A new dioxasilepine and aryldiamine hybrid material DPSi-DBDTA is designed to act as the electron-blocking layer (EBL) for vacuum-processed organic photodetector (OPD). The O-Si-O-linked cyclic structure leads DPSi-DBDTA to have dipolar character, high LUMO, and good thermal and morphology stability suitable for vacuum deposition. An initial trial with C₆₀-based single active layer OPD device manifests the superior capability of DPSi-DBDTA for dark current suppression compared to the typical aryldiamines. Here, the bare and MoO₃-doped DPSi-DBDTA is further examined as EBLs for the visible light responsive OPD comprising DTDCPB/C₇₀ bulk heterojunction (BHJ) as the active layer. In sync with the result of C₆₀-based OPD, the low dark current density and high specific detectivity D* (7.085 × 10¹² cm Hz^1/2 W^-1) are achieved. The device with 5% MoO₃-doped EBL can exhibit a wide linear dynamic range (LDR) up to 154.166 dB, which is attributed to suppression of both dark current density and carrier recombination. Additionally, the devices also manifest fast time-resolved performance in both frequency and transient response measurements. Especially for the device with 20% MoO₃-doped EBL, a wide cutoff frequency response 692.047 kHz and record-high transient response demonstrating ≤0.683 μs for transient photovoltage (TPV) and ≤0.478 μs for transient photocurrent (TPC) have been realized, which is possibly owing to the balance of mobility that mitigates the damage from traps. Such submicrosecond response is comparable with the state-of-the-art perovskite-PDs and Si-PDs.