The market for printed and flexible electronics, key attributes for internet of things, is estimated to reach $45 billion by 2016 and paper-based electronics shows great potential to meet this increasing demand due to its popularity, flexibility, low cost, mass productivity, disposability, and ease of processing. Solar-blind deep ultraviolet (DUV) photodetectors (PDs) can be widely applied in wearable applications such as military sensing, automatization, short-range communications security and environmental detection. In this work, we present flexible DUV paper PDs consisting of 2D boron nitride (h-BN) with good detectivity, fast recovery time (down to 0.393 s), great thermal stability (146 W/m K, 3-order-of-magnitude larger than conventional flexible substrates), high working temperature (up to 200 oC), excellent flexibility and bending durability (showing repeatable ON/OFF switching during 200-time bending cycles), which opens avenues to the flexible electronics.
Catalysts, chemical stability, and light harvesting are three major challenges in developing high performance photoelectrochemical water-splitting devices. Here we report the significant improvement of using bifacially designed schemes for achieving an ultrahigh solar to hydrogen efficiency of 18.22% with ultrafast hydrogen production rate and excellent chemical stability up to 370 hr. By deposition with appropriate catalyst (Pt) thickness, we have successfully balanced the trade-off among catalytic reaction, chemical protection, and light harvesting properties. In addition, the well-distributed catalytic and light harvesting sites provided by Si bifacial photoelectrochemical cells exhibit significantly higher omnidirectional hydrogen production capability as compared to conventional single-sided devices. Light-intensity dependent characterization is further demonstrated for realizing the bifacial photoelectrochemical cell in practical applications. The well-controlled, high efficiency, and chemically stable photoelectrochemical cell demonstrated herein can provide an important advance towards the development of next-generation renewable energy devices.