Refine
Has Fulltext
- no (25)
Year of publication
Language
- English (25)
Is part of the Bibliography
- yes (25)
Keywords
- solar cells (3)
- Aggregate states (1)
- All-polymer heterojunctions (1)
- Alternating copolymers (1)
- Ambipolar charge transport (1)
- Ambipolar materials (1)
- Backbone modifications (1)
- Bilayer solar cells (1)
- C60 (1)
- Charge separation (1)
- Conformational disorder (1)
- Crystalline phases (1)
- CsPbI2Br (1)
- Donor-acceptor copolymers (1)
- Electron traps (1)
- Energetic disorder (1)
- Energy-level alignment (1)
- Fermi-level alignment (1)
- Fermi-level pinning (1)
- Interface dipole (1)
- Interlayer (1)
- Intrachain order (1)
- Intragap states (1)
- Kelvin probe (1)
- Microscopic morphology (1)
- Mobility imbalance (1)
- Mobility relaxation (1)
- Monte Carlo simulation (1)
- Multiple trapping model (1)
- Nonradiative recombination (1)
- OFET (1)
- Open-circuit voltage (1)
- Optoelectronic properties (1)
- Partially alternating copolymers (1)
- Photo-CELIV (1)
- Photocurrent (1)
- Photovoltaic gap (1)
- Polymer intermixing (1)
- Recombination losses (1)
- Spectral diffusion (1)
- Statistical copolymers (1)
- Stille-type cross-coupling (1)
- Structure-property relationships (1)
- Time-dependent mobility (1)
- Time-of-flight (TOF) (1)
- Transient photocurrent (1)
- Ultraviolet photoelectron spectroscopy (1)
- Vacuum-level alignment (1)
- X-ray photoelectron spectroscopy (1)
- aggregation (1)
- charge accumulation (1)
- charge injection across hybrid interfaces (1)
- charge transfer (1)
- conducting polymers (1)
- crystalline ordering (1)
- defects (1)
- doping (1)
- efficiency potentials (1)
- electron-transport layers (1)
- energy-level alignments (1)
- field-effect-transistor (1)
- hybrid metal oxides (1)
- inorganic perovskites (1)
- interface recombination (1)
- lead halide perovskite films (1)
- loss mechanisms (1)
- morphology (1)
- naphthalenediimide (1)
- nonradiative recombination (1)
- open-circuit voltage (1)
- organic interfaces (1)
- organic photovoltaics (1)
- organic semiconductors (1)
- organohalide lead perovskites (1)
- oxygen plasma (1)
- perovskite solar cells (1)
- perovskites (1)
- photoluminescence (1)
- semiconducting polymers (1)
- surface band bending (1)
- surface photovoltage (1)
- surface states (1)
- surface wetting (1)
- thiophene (1)
- transport layer (1)
- ultraviolet photoelectron spectroscopy (1)
- voltage losses (1)
- work function (1)
Institute
Engineering the interface between the perovskite absorber and the charge-transporting layers has become an important method for improving the charge extraction and open-circuit voltage (V-OC) of hybrid perovskite solar cells. Conjugated polymers are particularly suited to form the hole-transporting layer, but their hydrophobicity renders it difficult to solution-process the perovskite absorber on top. Herein, oxygen plasma treatment is introduced as a simple means to change the surface energy and work function of hydrophobic polymer interlayers for use as p-contacts in perovskite solar cells. We find that upon oxygen plasma treatment, the hydrophobic surfaces of different prototypical p-type polymers became sufficiently hydrophilic to enable subsequent perovskite junction processing. In addition, the oxygen plasma treatment also increased the ionization potential of the polymer such that it became closer to the valance band energy of the perovskite. It was also found that the oxygen plasma treatment could increase the electrical conductivity of the p-type polymers, facilitating more efficient charge extraction. On the basis of this concept, inverted MAPbI(3) perovskite devices with different oxygen plasma-treated polymers such as P3HT, P3OT, polyTPD, or PTAA were fabricated with power conversion efficiencies of up to 19%.
The combined effect of ultraviolet (UV) light soaking and self-assembled monolayer deposition on the work function (WF) of thin ZnO layers and on the efficiency of hole injection into the prototypical conjugated polymer poly(3-hexylthiophen-2,5-diyl) (P3HT) is systematically investigated. It is shown that the WF and injection efficiency depend strongly on the history of UV light exposure. Proper treatment of the ZnO layer enables ohmic hole injection into P3HT, demonstrating ZnO as a potential anode material for organic optoelectronic devices. The results also suggest that valid conclusions on the energy-level alignment at the ZnO/organic interfaces may only be drawn if the illumination history is precisely known and controlled. This is inherently problematic when comparing electronic data from ultraviolet photoelectron spectroscopy (UPS) measurements carried out under different or ill-defined illumination conditions.
Inorganic perovskite solar cells show excellent thermal stability, but the reported power conversion efficiencies are still lower than for organic-inorganic perovskites. This is mainly caused by lower open-circuit voltages (V(OC)s). Herein, the reasons for the low V-OC in inorganic CsPbI2Br perovskite solar cells are investigated. Intensity-dependent photoluminescence measurements for different layer stacks reveal that n-i-p and p-i-n CsPbI2Br solar cells exhibit a strong mismatch between quasi-Fermi level splitting (QFLS) and V-OC. Specifically, the CsPbI2Br p-i-n perovskite solar cell has a QFLS-e center dot V-OC mismatch of 179 meV, compared with 11 meV for a reference cell with an organic-inorganic perovskite of similar bandgap. On the other hand, this study shows that the CsPbI2Br films with a bandgap of 1.9 eV have a very low defect density, resulting in an efficiency potential of 20.3% with a MeO-2PACz hole-transporting layer and 20.8% on compact TiO2. Using ultraviolet photoelectron spectroscopy measurements, energy level misalignment is identified as a possible reason for the QFLS-e center dot V-OC mismatch and strategies for overcoming this V-OC limitation are discussed. This work highlights the need to control the interfacial energetics in inorganic perovskite solar cells, but also gives promise for high efficiencies once this issue is resolved.
Perovskite semiconductors are an attractive option to overcome the limitations of established silicon based photovoltaic (PV) technologies due to their exceptional opto-electronic properties and their successful integration into multijunction cells. However, the performance of single- and multijunction cells is largely limited by significant nonradiative recombination at the perovskite/organic electron transport layer junctions. In this work, the cause of interfacial recombination at the perovskite/C-60 interface is revealed via a combination of photoluminescence, photoelectron spectroscopy, and first-principle numerical simulations. It is found that the most significant contribution to the total C-60-induced recombination loss occurs within the first monolayer of C-60, rather than in the bulk of C-60 or at the perovskite surface. The experiments show that the C-60 molecules act as deep trap states when in direct contact with the perovskite. It is further demonstrated that by reducing the surface coverage of C-60, the radiative efficiency of the bare perovskite layer can be retained. The findings of this work pave the way toward overcoming one of the most critical remaining performance losses in perovskite solar cells.