A low-bandgap (1.33 eV) Sn-based MA FA Pb Sn I perovskite is developed via combined compositional, process, and interfacial engineering. It can deliver a high power conversion efficiency (PCE) of 14.19%. Finally, a four-terminal all-perovskite tandem solar cell is demonstrated by combining this low-bandgap cell with a semitransparent MAPbI cell to achieve a high efficiency of 19.08%.

Wide bandgap MAPb(IBr) perovskites show promising potential for application in tandem solar cells. However, unstable photovoltaic performance caused by phase segregation has been observed under illumination when y is above 0.2. Herein, we successfully demonstrate stabilization of the I/Br phase by partially replacing Pb with Sn and verify this stabilization with X-ray diffractometry and transient absorption spectroscopy. The resulting MAPbSn(IBr) perovskite solar cells show stable photovoltaic performance under continuous illumination. Among these cells, the one based on MAPbSn(IBr) perovskite shows the highest efficiency of 12.59% with a bandgap of 1.73 eV, which make it a promising wide bandgap candidate for application in tandem solar cells. The engineering of internal bonding environment by partial Sn substitution is believed to be the main reason for making MAPbSn(IBr) perovskite less vulnerable to phase segregation during the photostriction under illumination. Therefore, this study establishes composition engineering of the metal site as a promising strategy to impart phase stability in hybrid perovskites under illumination.

The application of MOF materials in photovoltaic devices is comprehensively summarized and discussed.

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Organic photovoltaics (OPVs) have recently attracted extensive interest due to their potential for low cost, high throughput manufacturing to solve the scalability problem in solar energy. A typical OPV is based on the bulk-heterojunction (BHJ) device confi guration, which sandwiches a layer of polymer donor and fullerene acceptor blend between a transparent electrode (such as indium tin oxide (ITO)) and an opaque, refl ective metal electrode. These devices have shown high power conversion efficiencies (PCE) greater than 8%. [ 1 ] Semi-transparent organic photovoltaic cells (STOPVs), an extension of OPVs which utilize transparent conductive materials as both electodes, offer an extensive spectra of applications such as power-generating windows for buildings and automobiles, foldable solar curtains, and other aesthetic architectural uses. Furthermore, the capability of converting incident light to electric power shows the potential of STOPVs in the fi eld of effi cient energy conservation.When compared to vapor deposited small molecule STOPVs [ 2a ] or silicon-based STPVs, [ 2b ] the development of solution processed polymer-based STOPVs is lagging due to the absence of effi cient donor polymers and electrodes with proper transparency. STOPVs require more sophisticated materials and refi ned device engineering to simultaneously optimize both PCE and device transmittance, which are often contradictory to each other. In addition, for STOPVs to have practical solar window applications, good transparency perception (at least ≥ 20%) and color rendering properties are required under regular scene illumination. [ 2c ] To date, the state-of-the-art polymer-based STOPVs have either relatively low performance ( ≤ 3%) or unsatisfactory average visible transmittance (AVT) and color purity. [ 3 − 6 ] Therefore, there is a strong need to develop suitable polymer materials and novel device confi gurations to achieve improved PCE and transmittance for practical applications.In order for a device to have high PCE and transmittance in addition to proper color rendering index, it is critical to utilize appropriate thin BHJ layers that can effi ciently harvest the proper spectrum of light and electrodes with high transmittance and electrical conductivity. Until now, the frequently reported STOPVs still use a rather thick (at least 100 nm) poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PC 61 BM) based BHJ layer. The dominant absorption of P3HT is located in the yellow-green wavelength region (500 ∼ 600 nm) where human eyes have the highest sensitivity, therefore leading to poor color perception and rendering properties. [ 3,4,7,8 ] The optimal materials for solar window applications should have ample light absorption outside of regions where human eyes are the most sensitive; at the same time allowing transmittance of visible light extensively. As a result, polymers with a band-gap smaller than P3HT have become a viable option for STOPVs. [ 4 ] Although these STOPVs showed improved transparency perce...

In this study, we investigate the influence of molecular geometry of the donor polymers and the perylene diimide dimers (di‐PDIs) on the bulk heterojunction (BHJ) morphology in the nonfullerene polymer solar cells (PSCs). The results reveal that the pseudo 2D conjugated poly[4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b;4,5‐b′]dithiophene‐2,6‐diyl‐alt‐(4‐(2‐ethylhexyl)‐3‐fluorothieno[3,4‐b]thiophene‐)‐2‐carboxylate‐2‐6‐diyl)] (PTB7‐Th) has better miscibility with both bay‐linked di‐PDI (B‐di‐PDI) and hydrazine‐linked di‐PDI (H‐di‐PDI) compared to its 1D analog, poly[[4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl]] (PTB7), to facilitate more efficient exciton dissociation in the BHJ films. However, the face‐on oriented π–π stacking of PTB7‐Th is severely disrupted by the B‐di‐PDI due to its more flexible structure. On the contrary, the face‐on oriented π–π stacking is only slightly disrupted by the H‐di‐PDI, which has a more rigid structure to provide suitable percolation pathways for charge transport. As a result, a very high power conversion efficiency (PCE) of 6.41% is achieved in the PTB7‐Th:H‐di‐PDI derived device. This study shows that it is critical to pair suitable polymer donor and di‐PDI‐based acceptor to obtain proper BHJ morphology for achieving high PCE in the nonfullerene PSCs.

A versatile interconnecting layer (ICL) based on reflective ultra-thin Ag (8–14 nm) was developed to enable the fabrication of a series-connected micro-cavity tandem polymer solar cell with a PCE up to 11% and a EQEMAXof >90%.

1′,2′-j]picene (DDP, 1), a thermally and chemically stable helical arene, can be prepared from 1,4-bis[2-(arylethynyl)phenyl]benzene in four synthetic steps. Its helical backbone, which incorporates an oquinodimethane moiety, was verified by X-ray crystallography, and this structural feature results in a very high barrier to racemization (exceeding 50 kcal/mol). DDP possesses versatile and promising properties, including a small HOMO−LUMO energy gap (1.31 eV for the dimesitylsubstituted derivative 1ab), an electron spin resonance (ESR)active character, a small triplet−singlet energy gap (4.75 kcal/mol), broad photoabsorption covering the ultraviolet, visible, and near-infrared (NIR) regions, two-photon absorption in the NIR range, and respectable ambipolar charge-transport behavior in a solution-processed organic field-effect transistor.