Improving the Stability of Bulk Heterojunction Solar Cells by Incorporating pH-Neutral PEDOT:PSS as the Hole Transport Layer

In the application of traditional bulk heterojunction polymer solar cells, to prevent the etching of ITO by the acidic poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS) and thereby improve the device stability, pH-neutral PEDOT:PSS is introduced as the hole transport layer (HTL). After treating the neutral PEDOT:PSS with UV-ozone and with an oxygen plasma, the average power conversion efficiency (PCE) of the device increases from 3.44% to 6.60%. Such surface treatments reduce the energy level offset between the HTL and the active layer, which increases the open circuit voltage and enhances hole transportation, leading to the PCE improvement. Moreover, the devices with the neutral PEDOT:PSS HTL are more stable in air than those with the acidic PEDOT:PSS HTL. The PCE of the devices with the acidic PEDOT:PSS HTL decreases by 20% after 7 days and 45% after 50 days under ambient conditions, whereas the PCE of the devices with the pH-neutral PEDOT:PSS HTL decreases by only 9 and 20% after 7 and 50 days, respectively. X-ray photoelectron spectroscopy shows that the acidic PEDOT:PSS etches the indium from the indium–tin−oxide (ITO) electrode, which is responsible for the degradation of the device. In comparison, the diffusion of the indium is much slower in the devices with the pH-neutral PEDOT:PSS HTL

Balanced Ambipolar Organic Thin-Film Transistors Operated under Ambient Conditions: Role of the Donor Moiety in BDOPV-Based Conjugated Copolymers

Organic field-effect transistors (OFETs) are receiving an increased amount of attention because of their intriguing advantages such as flexibility, low cost, and solution processability. Development of organic conjugated polymers with balanced ambipolar carrier transportation operated under ambient conditions, in particular, is considered to be one of the central issues in OFETs. In this work, the 3,7-bis­[(<i>E</i>)-2-oxoindolin-3-ylidene]-3,7-dihydrobenzo­[1,2-<i>b</i>:4,5-<i>b</i>′]­difuran-2,6-dione (BDOPV) unit as a good acceptor unit was copolymerized with three donor moieties, thieno­[3,2-<i>b</i>]­thiophene (TT), benzo­[1,2-<i>b</i>:4,5-<i>b</i>′]­dithiophene (BDT), and benzo­[1,2-<i>b</i>:4,5-<i>b</i>′]­diselenophene (BDSe), to construct three donor–acceptor (D–A) conjugated polymers, <b>BDOPV–TT</b>, <b>BDOPV–BDT</b>, and <b>BDOPV–BDSe</b>. Photophysical and electrochemical properties of all the polymers were characterized. The fabrication of OFETs using three polymers as the active layers demonstrated that all the three polymers showed balanced ambipolar transport properties tested under ambient conditions, which is of great importance in complementary circuits. In particular, both electron and hole mobilities of <b>BDOPV–TT</b> were achieved above 1 cm² V^–1 s^–1 under ambient conditions (1.37 and 1.70 cm² V^–1 s^–1, respectively), showing great potential in balanced ambipolar OFETs

Electrochemically Assisted Construction of a La₂NiO_4+δ@Pt Core–Shell Structure for Enhancing the Performance and Durability of La₂NiO_4+δ Cathodes

Ruddlesden–Popper oxide La2NiO4+δ (LNO) has a high ionic conductivity and good thermal match with the electrolyte of solid oxide fuel cells (SOFCs); however, LNO suffers from performance decay owing to the La surface segregation under the operation conditions of SOFCs. Herein, we report an in situ electrochemical decoration strategy to improve the electrocatalytic activity and durability of LNO cathodes. We show that the electrochemical polarization leads to in situ construction of the LNO@Pt core–shell structure, significantly suppressing the detrimental effect of La surface segregation on the LNO cathode. The initial peak power density of a single cell with the LNO cathode is 0.71 W cm–2 at 750 °C, increasing to 1.39 W cm–2 by the in situ construction of the LNO@Pt core–shell structure after polarization at 0.5 A cm–2 for 20 h. The LNO@Pt core–shell structure is also highly durable without noticeable performance degradation over the duration of the test for 180 h. The findings shed light on the design and fabrication of highly active and durable LNO-based cathodes for SOFCs

Ultrafine, Dual-Phase, Cation-Deficient PrBa_0.8Ca_0.2Co₂O_5+δ Air Electrode for Efficient Solid Oxide Cells

Nanostructured air electrodes play a crucial role in improving the electrocatalytic activity of oxygen reduction and evolution reactions in solid oxide cells (SOCs). Herein, we report the fabrication of a nanostructured BaCoO3-decorated cation-deficient PrBa0.8Ca0.2Co2O5+δ (PBCC) air electrode via a combined modification and direct assembly approach. The modification approach endows the dual-phase air electrode with a large surface area and abundant oxygen vacancies. An intimate air electrode–electrolyte interface is in situ constructed with the formation of a catalytically active Co3O4 bridging layer via electrochemical polarization. The corresponding single cell exhibits a peak power density of 2.08 W cm–2, an electrolysis current density of 1.36 A cm–2 at 1.3 V, and a good operating stability at 750 °C for 100 h. This study provides insights into the rational design and facile utilization of an active and stable nanostructured air electrode of SOCs