Yang Yang (楊陽）

Vibrant research has demonstrated that the layer-by-layer (LBL) approach can achieve a preferable vertical microstructure; however, the lack of precise control over vertical composition and molecular organization remains. Herein, we demonstrated a guest polymer-tailored LBL (GPT-LBL) strategy to achieve the p-i-n microstructure constructed by in situ monitoring pre-aggregation behaviors of non-fullerene acceptors. This superior structure with built-in interpenetrating networks alleviates the trap density states and the energy loss, improves hole transfer dynamics, and balances the charge transport, thus maximizing open-circuit voltage (VOC), short-circuit current density (JSC), and fill factor (FF) simultaneously. Consequently, a highly efficient GPT-LBL organic solar cell (OSC) with a power conversion efficiency (PCE) of 19.41% (certified 19.0%) was achieved. Noticeably, the large-area (1.03 cm2) device for GPT …

The black phase of formamidinium lead iodide (FAPbI3) perovskite shows huge promise as an efficient photovoltaic, but it is not favoured energetically at room temperature, meaning that the undesirable yellow phases are always present alongside it during crystallization, , –. This problem has made it difficult to formulate the fast crystallization process of perovskite and develop guidelines governing the formation of black-phase FAPbI3 (refs. ,). Here we use in situ monitoring of the perovskite crystallization process to report an oriented nucleation mechanism that can help to avoid the presence of undesirable phases and improve the performance of photovoltaic devices in different film-processing scenarios. The resulting device has a demonstrated power-conversion efficiency of 25.4% (certified 25.0%) and the module, which has an area of 27.83 cm2, has achieved an impressive certified aperture efficiency of 21.4%.

Non-fullerene acceptors based organic solar cells represent the frontier of the field, owing to both the materials and morphology manipulation innovations. Non-radiative recombination loss suppression and performance boosting are in the center of organic solar cell research. Here, we developed a non-monotonic intermediate state manipulation strategy for state-of-the-art organic solar cells by employing 1,3,5-trichlorobenzene as crystallization regulator, which optimizes the film crystallization process, regulates the self-organization of bulk-heterojunction in a non-monotonic manner, i.e., first enhancing and then relaxing the molecular aggregation. As a result, the excessive aggregation of non-fullerene acceptors is avoided and we have achieved efficient organic solar cells with reduced non-radiative recombination loss. In PM6:BTP-eC9 organic solar cell, our strategy successfully offers a record binary organic solar …

Semi-transparent organic photovoltaics (OPVs) are an emerging solar-energy-harvesting technology with promising applications, such as rooftop energy supplies for environmentally friendly greenhouses. However, the poor operational stability of OPVs poses challenges to their feasibility as incessantly serving facilities. Here we report a reductive interlayer structure for semi-transparent OPVs that improves the operational stability of OPVs under continuous solar radiation. The interlayer effectively suppresses the generation of radicals from the electron transport layer under sunlight and prevents the structural decomposition of the organic photoactive layer during operation. The defects that serve as the charge carrier recombination sites are nullified by the electron-donating functional groups of the reduced molecules, which improves photovoltaic performance. The semi-transparent OPVs demonstrate a power …

Cations with suitable sizes to occupy an interstitial site of perovskite crystals have been widely used to inhibit ion migration and promote the performance and stability of perovskite optoelectronics. However, such interstitial doping inevitably leads to lattice microstrain that impairs the long-range ordering and stability of the crystals, causing a sacrificial trade-off. Here, we unravel the evident influence of the valence states of the interstitial cations on their efficacy to suppress the ion migration. Incorporation of a trivalent neodymium cation (Nd3+) effectively mitigates the ion migration in the perovskite lattice with a reduced dosage (0.08%) compared to a widely used monovalent cation dopant (Na+, 0.45%). The photovoltaic performances and operational stability of the prototypical perovskite solar cells are enhanced with a trace amount of Nd3+ doping while minimizing the sacrificial trade-off.

Solar energy offers an alternative solution to the global community's growing energy demands. Semitransparent organic photovoltaics (ST‐OPVs) have received tremendous attention due to their tunable energy levels and rising power conversion efficiency (PCE). Because of its transparency, ST‐OPVs are able to serve as the power‐generating roof of the greenhouse, and color‐tunable walls/windows for modern buildings or façades. With the rapid development of narrow‐bandgap semiconductors to absorb near‐infrared photons, the performances of ST‐OPVs has progressed with PCEs over 12% with average visible transmittances over 20%. Here, recent developments in ST‐OPVs based on narrow‐bandgap donors and non‐fullerene acceptors are reviewed. Several strategies for chemical structures design have been reported to lower bandgaps semiconductor materials. The recent developments of non …

Optoelectronic devices consist of heterointerfaces formed between dissimilar semiconducting materials. The relative energy-level alignment between contacting semiconductors determinately affects the heterointerface charge injection and extraction dynamics. For perovskite solar cells (PSCs), the heterointerface between the top perovskite surface and a charge-transporting material is often treated for defect passivation, , – to improve the PSC stability and performance. However, such surface treatments can also affect the heterointerface energetics. Here we show that surface treatments may induce a negative work function shift (that is, more n-type), which activates halide migration to aggravate PSC instability. Therefore, despite the beneficial effects of surface passivation, this detrimental side effect limits the maximum stability improvement attainable for PSCs treated in this way. This trade-off between the beneficial …

Due to their solution processability and unique photoelectric characteristics, perovskite solar cells (PSCs) have shown considerable promise in the area of renewable energy. Although their power conversion efficiency (PCE) has risen from 3.8% to 25.7% in only a few years, their short lifetime and high material prices continue to be key roadblocks to commercial viability. Charge transporting materials (CTMs), such as hole/electron transporting materials, are critical components in PSCs because they not only govern hole or electron extraction and transporting from the perovskite layer to the electrodes but also protect the perovskite from direct contact with the ambient environment. CTMs are split into two types: inorganic CTMs (ICTMs) and organic CTMs (OCTMs). Because of their inexpensive prices, well-adjusted energy levels, and low temperature solution-processed features, OCTMs have been more frequently …

Near‐infrared (NIR)‐absorbing organic semiconductors have opened up many exciting opportunities for organic photovoltaic (OPV) research. For example, new chemistries and synthetical methodologies have been developed; especially, the breakthrough Y‐series acceptors, originally invented by our group, specifically Y1, Y3, and Y6, have contributed immensely to boosting single‐junction solar cell efficiency to around 19%; novel device architectures such as tandem and transparent organic photovoltaics have been realized. The concept of NIR donors/acceptors thus becomes a turning point in the OPV field. Here, the development of NIR‐absorbing materials for OPVs is reviewed. According to the low‐energy absorption window, here, NIR photovoltaic materials (p‐type (polymers) and n‐type (fullerene and nonfullerene)) are classified into four categories: 700–800 nm, 800–900 nm, 900–1000 nm, and greater …

Mechanically resilient optoelectronic devices are relevant for a wide range of applications, including portable and wearable devices. Perovskite thin film‐based devices are a suitable choice for designing such resilient systems as it demonstrates high performance while preserving moderate mechanical compliance. Yet its mechanical property can be improved further by integrating the energy dissipation system and self‐healing ability into the thin film. Copolymers containing Lewis‐base functional groups, elastomer chains, and cyclic linkages are synthesized and introduced into the perovskite precursor. The polymers impart multifunctional effect of controlled crystal growth, defect passivation, protection against moisture, mechanical energy dissipation, and self‐recoverability. The polymer‐added perovskite solar cells are shown to provide a power conversion efficiency of 23.25% (a steady‐state efficiency of 22.61 …

The A cation in ABX3 organic-inorganic lead halide perovskites (OLHPs) was conventionally believed to hardly affect their optoelectronic properties. However, more recent developments have unraveled the critical role of the A cation in the regulation of the physicochemical and optoelectronic properties of OLHPs. We review the important breakthroughs enabled by the versatility of the A cation and highlight potential opportunities and unanswered questions related to the A cation in OLHPs.

Tedious trial-and-error procedures are commonly practiced for surface modification of the perovskite solar cell (PSC) active layers. A guideline to rationally choose the passivating functional groups of the polymeric structure that is eminently effective in passivating the charged defects and elongating the device lifetime is hence in urgent demand. Herein, three prototypical polymers, poly(vinyl acetate) (PVA), polyethylene glycol (PEG), and poly(9-vinylcarbazole) (PVK), are selected to investigate the structural effect of the polymeric modification agents on the PSCs. We found that PVA possesses the Lewis base functional group with the minimized steric hindrance and the strongest electron-donating ability, enabling the most effective defect passivation on the perovskite film surface and the most enhanced carrier diffusion capacity. It demonstrates a power conversion efficiency (PCE) of 23.20% and noticeably …

Superior bandgap tunability enables solution‐processed halide perovskite a promising candidate for multi‐junction photovoltaics (PVs). Particularly, optically coupling wide‐gap perovskite by stacking with commercially available PVs such as silicon and CIGS (also known as 4‐terminal tandem) simplifies the technology transfer process, and further advances the commercialization potential of perovskite technology. However, compared with matured PV materials and the phase‐pure FAPbI3, wide‐gap perovskite still suffers from huge voltage deficits. Here, the authors take advantage of the synergetic effect behind a sequential fluoride and organic ammonium salt surface passivation strategy to control non‐radiative energy losses, and obtained a 17.7% efficiency in infrared‐transparent wide‐gap perovskite solar cells (21.1% for opaque device), and achieved efficiencies of over 25% when stacked with commercial Si …

Revisiting the intensity-dependent quantum efficiency (IDQE) technique in the context of non-fullerene acceptors, we find that at forward-bias conditions, the response exhibits what seems to be anomalous behavior that is not consistent with light excitation induced trap filling. Analysis based on the Shockley–Read–Hall model leads to the conclusion that the contacts cause the traps to be completely full in the dark. The role of the light excitation is to half-empty the traps, and thus, the “anomalous” behavior is created. By fitting the IDQE at several bias levels, we find that the trapping is consistent with multiphonon capture by a state close to the middle of the gap. As trap-assisted recombination is a significant loss mechanism, it is essential to fully monitor it for indoor applications as well as to cross the single junction 20% power conversion efficiency limit.

Semitransparent organic photovoltaics (OPVs) have drawn significant attention for their promising potential in the field of building integrated photovoltaics such as energy-generating greenhouses. However, the conflict between the need to attain satisfying average visible transmittances for greenhouse applications and the need to maintain high power conversion efficiencies is limiting the commercialization of semitransparent OPVs. A major manifestation of this issue is the undermining of charge carrier extraction efficiency when opaque, visible-light-absorbing electrodes are substituted with semitransparent ones. Here, we incorporated a dual-function p-type compatible interlayer to modify the interface of the hole-transporting layer and the ultrathin electrode of the semitransparent devices. We find that the p-type interlayer not only enhances the charge carrier extraction of the electrode but also increases the light …

We computationally investigate the impact of crystal strain on the formation of native point defects likely to be formed in halide perovskites; A-site cation antisite (IA), Pb antisite (IPb), A-site cation vacany (VA), I vacancy (VI), Pb vacancy (VPb), and I interstitial We systematically identify compressive and tensile strain to CsPbI3, FAPbI3, and MAPbI3 perovskite structures. We observe that while each type of defect has a unique behaviour, overall, the defect formation in FAPbI3 is much more sensitive to the strain. The compressive strain can enhance the formation energy of neutral IPb and Ii up to 15% for FAPbI3, depending on the growth conditions. We show that the strain not only controls the formation of defects but also their transition levels in the band gap: A deep level can be transformed into a shallow level by the strain. We anticipate that tailoring the lattice strain can be used as a defect passivation mechanism for …

The electrochemical splitting of water into hydrogen and oxygen is considered one of the most promising approaches to generate clean and sustainable energy. However, the low efficiency of the oxygen evolution reaction (OER) acts as a bottleneck in the water splitting process. Herein, interface engineering heterojunctions between ZIF‐67 and layered double hydroxide (LDH) are designed to enhance the catalytic activity of the OER and the stability of Co‐LDH. The interface is built by the oxygen (O) of Co‐LDH and nitrogen (N) of the 2‐methylimidazole ligand in ZIF‐67, which modulates the local electronic structure of the catalytic active site. Density functional theory calculations demonstrate that the interfacial interaction can enhance the strength of the CoOout bond in Co‐LDH, which makes it easier to break the H‐Oout bond and results in a lower free energy change in the potential‐determining step at the …

In this paper, a universal approach toward constructing a new bilayer device architecture, a few-nanometer-thick third-component layer on a bulk-heterojunction (BHJ) binary blend layer, has been demonstrated in two different state-of-the-art organic photovoltaic (OPV) systems. Through a careful selection of a third component, the power conversion efficiency (PCE) of the device based on PM6/Y6/layered PTQ10 layered third-component structure was 16.8%, being higher than those of corresponding devices incorporating the PM6/Y6/PTQ10 BHJ ternary blend (16.1%) and the PM6/Y6 BHJ binary blend (15.5%). Also, the device featuring PM7/Y1-4F/layered PTQ10 layered third-component structure gave a PCE of 15.2%, which is higher than the PCEs of the devices incorporating the PM7/Y1-4F/PTQ10 BHJ ternary blend and the PM7/Y1-4F BHJ binary blend (14.2 and 14.0%, respectively). These enhancements in …

Over the past decade, metal halide perovskite photovoltaics have been a major focus of research, with single-junction perovskite solar cells evolving from an initial power conversion efficiency of 3.8% to reach 25.5%. The broad bandgap tunability of perovskites makes them versatile candidates as the subcell in a tandem photovoltaics architecture. Stacking photovoltaic absorbers with cascaded bandgaps in a multi-junction device can potentially overcome the Shockley–Queisser efficiency limit of 33.7% for single-junction solar cells. There is now intense activity in developing tandem solar cells that pair perovskite with either itself or with a variety of mature photovoltaic technologies such as silicon and Cu(In,Ga)(S,Se)2 (CIGS). In this review, we survey recent advances in the field and discuss its outlook.

The past decade has witnessed the unprecedented boost of power conversion efficiency (PCE) of photovoltaics based on halide perovskite materials since its early discovery. Despite its remarkably good performance, long-term stability is yet one of the last barriers before commercializing halide perovskite photovoltaics is possible. In this perspective, we discuss the challenges and concurrently the strategies regarding the stability of the perovskite materials, photoactive crystal phases, and the performance as well as stability limiting interfaces. Future perspectives of stable halide perovskite and perovskite solar cells are also proposed to shine light on letting perovskite technology satisfy long-term operation warranty.