Progress of Photocapacitors.

In response to the current trend of miniaturization of electronic devices and sensors, the complementary coupling of high-efficiency energy conversion and low-loss energy storage technologies has given rise to the development of photocapacitors (PCs), which combine energy conversion and storage in a single device. Photovoltaic systems integrated with supercapacitors offer unique light conversion and storage capabilities, resulting in improved overall efficiency over the past decade. Consequently, researchers have explored a wide range of device combinations, materials, and characterization techniques. This review provides a comprehensive overview of photocapacitors, including their configurations, operating mechanisms, manufacturing techniques, and materials, with a focus on emerging applications in small wireless devices, Internet of Things (IoT), and Internet of Everything (IoE). Furthermore, we highlight the importance of cutting-edge materials such as metal-organic frameworks (MOFs) and organic materials for supercapacitors, as well as novel materials in photovoltaics, in advancing PCs for a carbon-free, sustainable society. We also evaluate the potential development, prospects, and application scenarios of this emerging area of research.

Dopant-Free Hole-Transport Materials with Germanium Compounds Bearing Pseudohalide and Chalcogenide Moieties for Perovskite Solar Cells.

Hole-transport materials (HTMs) are key electronic components for the functioning of perovskite solar cells (PSCs) as they extract the photogenerated holes from the perovskite to be transported subsequently to the back electrode while minimizing the loss from electron recombination. Herein, we report the synthesis and characterization of novel germanium-based compounds with [{HC(CMeNAr)2}GeNCS] (2), [{HC(CMeNAr)2}Ge(S)NCS] (3), and [{HC(CMeNAr)2}Ge(Se)NCS] (4) compositions, with Ar = 2,6-iPr2C6H3 and the photovoltaic performance of 3 and 4 that is the same as for HTM in PSC. All compounds displayed excellent thermal properties and an appropriate alignment of energy levels for the perovskite with maximum optical absorption in the near-UV region. As revealed by space-charge limited-current (SCLC) measurements, compounds 3 and 4 have competing hole mobilities of about 1.37 × 10-4 and 4.88 × 10-4 cm2 V-1 s-1, respectively. Upon assessing PSC devices using 3 and 4 with triple-cation perovskite absorber Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3, the power conversion efficiencies (PCEs) were about 13.03 and 9.23%, respectively, both without doping and additives, and were compared with benchmark HTM spiro-OMeTAD (2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene). Quantum chemical calculations with DFT showed that the optoelectronic properties are strongly influenced by the combined contributions of the germanium atom, the pseudohalide moiety (NCS-), and chalcogenides (S2- or Se2-). Fine tuning the electronic properties of germanium is thus a good strategy for the targeted synthesis of potential conducting molecules in PSCs.