High-performance PBT7-Th:PC70BM polymer photodiode with transferred charge blocking layers

We demonstrated a high performance low-bandgap organic polymer photodiode (OPD), with broadband spectrum, with transferred charge blocking layers. Besides the popular P3HT:PCBM bulk heterojucnction (BHJ) system, we investigated the OPD performance of PTB7-Th:PC70BM BHJ active layer with transfer printed charge blocking layer. To achieve higher performance OPD with lower dark current and higher responsivity, various device structures employing hole blocking layer (HBL) or and electron blocking layer (EBL) were investigated. A very low dark current of ∼5 nA/cm2 at reverse bias 0.5 V was achieved with BHJ active layer sandwiched between both HBL and EBL resulting in high specific detectivity of 1.48 × 1013 Jones at 700 nm. In addition, critical noise current measurement of the OPD was done to evaluate more accurately Noise Equivalent Power (NEP) value. It turned out that the shot noise is dominant over the thermal noise in the OPD verified by the in-depth noise analysis. More deliberate design of the device structure can deliver higher performance OPD cell with developed transfer printing method for use in organic photodetectors image sensors.