Wide-bandgap (WBG) perovskite solar cells (PSCs) with high performance and stability are in considerable demand in the photovoltaic market to boost tandem solar cell e ciencies. Perovskite bandgap broadening results in a high barrier for enhancing the e ciency of the PSCs and causes phase segregation in perovskite. In this study, we show that the residual strain is the key factor affecting the WBG perovskite device e ciency and stability. The DMSO addition not only helps lead halide to with opening the vertical layer spacing to form (CsI)0.08(PbI1.4Br0.6) and (CsI0.125Br0.875)0.08(PbI1.2Br0.8) intermediate phases, but also provide more nucleation sites to eliminate lattice mismatch with FAX (X = I, Br or Cl) or MAX, which dominates the strain effects on the WBG perovskite growth in a sequential deposition. By minimizing the strain, 1.67-and 1.77-eV nip devices with record e ciencies of 22.28% and 20.45%, respectively, can be achieved. The greatly enhanced suppression of phase segregation enables the device with retained 90% -95% of initial e ciency over 4000 h of damp stability and 80% -90% of initial e ciency over 700 h of maximum-power-point output stability under full-spectrum light without encapsulation. Besides, the 1.67-eV pin devices can achieve a competitive 22.3% e ciency while achieving considerable damp-heat, pre-ultraviolet (pre-UV) aging, and MPP tracking stability as per the tests conducted according to IEC 61215. The nal e ciency for the perovskite/Si tandem is more than 28.3 %, which matches the top e ciencies reported to date.

Wide‐bandgap perovskite solar cells (PSCs) with an optimal bandgap between 1.7 and 1.8 eV are critical to realize highly efficient and cost‐competitive silicon tandem solar cells (TSCs). However, such wide‐bandgap PSCs easily suffer from phase segregation, leading to performance degradation under operation. Here, it is evident that ammonium diethyldithiocarbamate (ADDC) can reduce the detrimental I2 back to I− in precursor solution, thereby reducing the density of deep level traps in perovskite films. The resultant perovskite film exhibits great phase stability under continuous illumination and 30–60% relative humidity conditions. Due to the suppression of defect proliferation and ion migration, the PSCs deliver great operation stability which retain over 90% of the initial power conversion efficiency (PCE) after 500 h maximum power point tracking. Finally, a highly efficient semitransparent PSC with a tailored bandgap of 1.77 eV, achieving a PCE approaching 18.6% with a groundbreaking open‐circuit voltage (VOC) of 1.24 V enabled by ADDC additive in perovskite films is demonstrated. Integrated with a bottom silicon solar cell, a four‐terminal (4T) TSC with a PCE of 30.24% is achieved, which is one of the highest efficiencies in 4T perovskite/silicon TSCs.

Direct chemical vapor deposition (CVD) of graphene on any desired substrate is always required to manufacture high-quality heterojunctions with excellent interfacial properties. Herein, the growth of graphene on cubic-silicon carbide (3C-SiC) surfaces using conventional high-temperature direct thermal CVD and plasma-enhanced CVD (PECVD) is explored, which is hardly reported to date. Since 3C-SiC substrates are not available, the controlled self-limited 3C-SiC layers on the Si(100) substrates were grown at different temperatures (900−1200 °C) via thermal-CVD technique to obtain virtual 3C-SiC substrates. The direct production of graphene via thermal CVD could not be achieved on such 3C-SiC surfaces. The density functional theory and molecular dynamics simulations confirm that the carbon atom diffusion over the 3C-SiC surface is extremely low, like over the Si surface, which leads to no graphene growth. A similar growth mechanism may be attributed to their similar crystal structure viz diamond cubic for Si and zinc blend for 3C-SiC. However, graphene nanowalls (GNWs) were successfully grown on both Si and 3C-SiC/Si surfaces at 700 °C via the PECVD technique, where similar surface morphologies were observed because the growth mechanism of GNWs is independent of substrate type. Moreover, I−V characterization was performed for different SiC/Si heterostructures and their corresponding GNWs/SiC/Si heterostructures, respectively. The current conduction improved considerably more for GNW/SiC/Si heterostructures as compared to SiC/Si heterostructures, but the creation of a SiC interfacial layer as well as its quality affected the conductivity of GNWs/SiC/Si heterostructures. The inevitable formation of an interfacial SiC layer during the direct graphene growth via thermal CVD on Si substrates can seriously affect the performance of graphene/Si heterojunction devices. Hence, PECVD growth of graphene is an ideal option to fabricate graphene/Si heterojunction devices with excellent interfacial properties or graphene/3C-SiC/Si heterojunction devices for various electronic/optoelectronic applications such as gas sensors and photovoltaic devices.

Repeated tandem electro-oxidative C−C and C−N coupling and aromatization were employed for the efficient construction of aza[7]helicene (BA7) as a key intermediate and the targeted pyrazine-fused bis-aza[7]helicene (PBBA7) derivatives in 90.0−93.2% isolated yields under a controlled potential. The electrosynthetic protocol showed high selectivity and enabled rapid access to functionalized organic conjugated materials from readily available polycyclic aromatic amines. A synthetic mechanistic study along with an investigation of the photoelectrical properties and application of PBBA7-C16 as a potential hole-transporting material for perovskite solar cells were performed.

Photodetectors (PDs) are widely used in various fields of military and daily life especially for imaging, telecommunications, sensing, and so on. Therefore, high performance and low power consumption are of crucial importance for PDs with high detectivity and fast response speed. Self-powered PDs have the advantage of low cost, which can be fabricated by the direct contact of graphene and silicon (Si). However, the graphene/Si Schottky structure suffers from the interface trap states and low Schottky junction barrier. Such drawbacks reduce the response speed and increase the noise current, which eventually hinder high-performance applications of PDs. In this study, 2,2′,7,7′-tetrakis­(N,N′-di-p-methoxyphenylamine)-9,9′-spirobiuorene (spiro-OMeTAD) was selected as an interfacial layer due to its suitable molecular orbital positions and excellent optical properties. The fabricated graphene/Si heterostructure PD with a spiro-OMeTAD interfacial layer showed an extremely high ON/OFF ratio over 107 at 0 V bias and a fast response of ∼5.1 μs. Moreover, it also exhibited a high specific detectivity of ∼8.7 × 1010 Jones, which was many-fold higher than the PD without the interfacial layer. Furthermore, the responsivity was obtained as 0.355 A/W at 532 nm illumination with 145 μW power. Hence, these results show a flexible approach to improve the performance of graphene/Si heterostructure-based PDs by using an organic interfacial layer.