Insulating Polymer Optimized Vertical Phase Separation Enables Organic Bulk Heterojunction Thick-Film Direct X-ray Detectors with Improved Sensitivity and Flexibility

Abstract

Compared to inorganic alternatives, organic semiconducting films show potential for developing flexible, large-area ionizing radiation detectors, thanks to their tissue equivalence, ease of processing, and ability for mass production. Identifying the key factors linking structure and device performance is thus crucial for optimizing the design of organic active layers. Herein, direct X-ray detectors with thick organic active layers are developed, featuring optimized vertical phase separation achieved through the addition of insulating polymer additives. The insulating polymer acts as a structural support in the thick film of the active layer, effectively facilitating the vertical separation of the donor and acceptor phase and preventing it from settling at the bottom. The sensitivity of the 5.12 μm-thick BHJ-PDMS-based detector reaches 4.75 × 10³ μC Gy_air^–1 cm^–2 (X-ray tube voltage = 10 kV) with a detection limit of 137.2 nGy_air s^–1. Finally, mechanical flexibility of the detector improved significantly from 4000 to 8000 cycles (radius = 5 mm). A 10 × 10 pixels imager array has been fabricated, and the imaging performance of the device has been evaluated. The broadly applicable strategy developed in this work enhances both the flexibility and the detection performance in organic flexible direct X-ray detectors, facilitating their practical use and advancing emerging technologies.