Organic-inorganic hybrid perovskite solar cells have emerged as one of the promising photovoltaic candidates to generate renewable energy. However, the large amounts of grain boundaries and trap states that exist in the bulk or interfacial regions of perovskite films limit further enhancement of device efficiency. Herein, an additive engineering strategy is introduced employing trimethylammonium chloride in the methylammonium iodide precursor solution to prepare methylammonium lead iodide perovskite films with reduced grain boundaries and trap densities. This leads to an increased charge carrier diffusion coefficient and diffusion length, as evaluated by impedance and voltage decay measurements, intensity-modulated photovoltage, and photocurrent spectroscopies. The proportion of nonradiative recombination processes is significantly reduced, consequently increasing device efficiency from 19.1% to 20.9% in these perovskite solar cells.
A major limit for planar perovskite solar cells is the trap‐mediated hysteresis and instability, due to the defective metal oxide interface with the perovskite layer. Passivation engineering with fullerenes has been identified as an effective approach to modify this interface. The rational design of fullerene molecules with exceptional electrical properties and versatile chemical moieties for targeted defect passivation is therefore highly demanded. In this work, novel fulleropyrrolidine (NMBF‐X, XH or Cl) monomers and dimers are synthesized and incorporated between metal oxides (i.e. TiO2, SnO2) and perovskites (i.e. MAPbI3 and (FAPbI3)x(MAPbBr3)1‐x). The fullerene dimers provide superior stability and efficiency improvements compared to the corresponding monomers, with chlorinated fullerene dimers being most effective at coordinating with both metal oxides and perovskite via the chlorine terminals. The non‐encapsulated planar device delivers a maximum power conversion efficiency of 22.3% without any hysteresis, while maintaining over 98% of initial efficiency after ambient storage for 1000 h, and exhibiting an order of magnitude improvement of the T80 lifetime.
The photovoltaic performance of inorganic perovskite solar cells (PSCs) still lags behind the organic–inorganic hybrid PSCs due to limited light absorption of wide bandgap CsPbI3‑xBr x under solar illumination. Constructing tandem devices with organic solar cells can effectively extend light absorption toward the long-wavelength region and reduce radiative photovoltage loss. Herein, we utilize wide-bandgap CsPbI2Br semiconductor and narrow-bandgap PM6:Y6-BO blend to fabricate perovskite/organic tandem solar cells with an efficiency of 21.1% and a very small tandem open-circuit voltage loss of 0.06 V. We demonstrate that the hole transport material of the interconnecting layers plays a critical role in determining efficiency, with polyTPD being superior to PBDB-T-Si and D18 due to its low parasitic absorption, sufficient hole mobility and quasi-Ohmic contact to suppress charge accumulation and voltage loss within the tandem device. These perovskite/organic tandem devices also display superior storage, thermal and ultraviolet stabilities.
CsPbX 3 nanocrystal (NC)-based blue perovskite light-emitting diodes (PeLEDs) are still in a backward position while their green and red counterparts have achieved significant progress in the past few years. The emission spectrum of perovskite NCs can be manipulated via the ratio control of halides in precursor or halogen exchange of NCs. Herein, CsPbBr x Cl 3−x NCs are synthesized in ambient condition. With tetrabutylammonium p-toluenesulfonate (TBSA) added as the ligand during the purification process of assynthesized perovskite NCs, bromine in NCs is substituted by chlorine and the spectrum undergoes a blue shift, whereas chlorine is exchanged by bromine in NCs and the spectrum undergoes a red shift by introducing sodium dodecylbenzenesulfonate (SDSA) as the ligand. The origin for halogen exchange can be attributed to the synergistic effects of the anion and cation of benzenesulfonates. The photoluminescence quantum yield (PLQY) of NCs increases from 7% to 81% due to the effective passivating effects of the strong ionic sulfonate heads, and the blue PeLEDs prepared by this method show a promising external quantum efficiency of 2.6%. Our work provides a new approach into spectral tuning of efficient blue PeLEDs.
Besides the intrinsic optoelectronic properties of photovoltaic materials and the device architectures, the nanoscale morphology within the photoactive layer, including molecular packing in molecule level and molecular aggregation in nanoscale, [12][13][14][15][16] represents a vital factor in optimizing the device performance and can be manipulated via various approaches. [17][18][19][20][21][22][23][24] It is known that the pre-aggregates of organic semiconductors in solution have a profound influence toward their morphology in solid thin films, and various physical and chemical approaches, including the modulation of solvent, [25] solvent additive, [26] temperature [27] and molecular structure, [28,29] have been demonstrated in the literature to manipulate the pre-aggregation behavior. [13,30] For example, additives can induce polymer aggregates with short range order in solution, which can then act as the nuclei for polymer crystallization during the solution casting process, leading to many small polymer domains with jagged interfaces, resulting in enhanced light harvesting and charge separation. [31] Co-solvents have been used to induce polymer aggregation and prevent the formation of large domains of fullerene as well as restraining the liquidliquid phase separation in PDPP5T:PC 70 BM system in order to receive high performance. [32] Ma et al. controlled the solution and substrate temperatures during the casting of PM6:Y6 from hydrocarbon solvents to enable similar aggregation states in solutions and solid films compared to those cast from halogenated solution, and therefore maintained the device PCE cast from hydrocarbon solvents. [33] Zhang et al. tuned the molecular weight of PM6 to optimized OSCs with suitable size and purity of the domains to achieve well-balanced charge transport, and found that PM6 with higher molecular weight possessed a stronger aggregation degree in solutions. [34] The temperature-dependent aggregation property of conjugated polymers offers the approach to manipulate the pre-aggregation through temperature control, which is also a facile and low-cost approach. [35,36] Different from previous work on tuning the aggregation in a temperature range from room-temperature to over 100 °C, weThe molecular ordering and pre-aggregation of photovoltaic materials in solution can significantly affect the nanoscale morphology in solid photoactive layers, and play a vital role in determining the power conversion efficiency (PCE) of organic solar cells (OSCs). Herein, a cold-aging strategy is reported to mediate the pre-aggregation of PM6 polymer in solution through a disorder-order transition, which leads to dense and fine PM6 aggregates with enhanced π−π stacking in its blend thin films with either fused-ring and non-fused-ring non-fullerene acceptors (NFAs) including Y6-BO, N3, IT-4F, and PTIC. The fine aggregates of PM6 and slightly enlarged NFA domains improve the continuous networks with enhanced and balanced charge mobility. The resulting OSCs all demonstrate enhanced PCEs compared to the...
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