No abstract

We quantified non-radiative recombination loss and charge transfer loss for acetamidine halide passivated perovskite solar cells.

It is crucial to finely optimize the properties of hole transport materials (HTMs) to improve the performance and stability of perovskite solar cells (PSCs). Herein, a new spiro‐based HTM (Spiro‐4TFETAD) is developed by replacement of partial methoxy groups in Spiro‐OMeTAD with trifluoroethoxy substituents. Spiro‐4TFETAD has lower highest occupied molecular orbital level, higher thermal stability (Tg = 140 °C), hole mobility (2.04 × 10−4 cm2 V−1 s−1), and better hydrophobicity with respect to Spiro‐OMeTAD. The PSCs using Spiro‐4TFETAD achieve a power conversion efficiency of 21.11% and excellent humidity resistance. It maintains an average 83% of their initial power conversion efficiency values even in high relative humidity of 60% without encapsulation and 82% of its initial performance after 100 h continuous illumination at the maximum power point. The superior performance underscores the promising potential of the trifluoroethoxyl molecular design in preparing new HTMs toward highly efficient and stable PSCs.

commercial silicon photovoltaic technology, which has achieved certified champion power conversion efficiency (PCE) of 25.7% in single-junction PSCs and 29.8% in tandem with silicon solar cells. [1,2] However, defects from the contact interfaces and the bulk in the polycrystalline perovskites films are the primary causes of carrier recombination loss and the instability of films and devices. [3][4][5] The chloride compounds are often used to enhance the performance by strengthening the film quality and eliminating defects. The better film quality is generally realized by controlling the crystallization process and grain size distribution, and stabilizing α-phase FAPbI 3 , respectively. For example, CH 3 NH 3 Cl (MACl) additive directs the growth to form intermediates for fabricating more stable perovskite and increasing the diffusion length to >1 µm. [6] A series of chloride compounds as additives or passivators were also introduced to lessen the defects. [7][8][9][10] To further understand the improvement mechanism, the spatial distribution of chloride compounds has been examined at different locations. The chloride of Cl-containing perovskite tended to be dispersed close to the perovskite/TiO 2 buried contact, according to the research from Starr and coworkers. [11] Pb-I anti-site deep-level defects at the Post-treatment is an essential passivation step for the state-of-the-art perovskite solar cells (PSCs) but the additional role is not yet exploited. In this work, perovskite film is fabricated under ambient air with wide humidity window and identify that chloride redistribution induced by post-treatment plays an important role in high performance. The chlorine/iodine ratio on the perovskite surface increases from 0.037 to 0.439 after cyclohexylmethylammonium iodide (CHMAI) treatment and the PSCs deliver a champion power conversion efficiency (PCE) of 24.42% (certificated 23.60%). The maximum external quantum efficiency of electroluminescence (EQE EL ) reaches to 10.84% with a radiance of 170 W sr −1 m −2 , forming the reciprocity relation between EQE EL and nonradiative open-circuit voltage loss (86.0 mV). After thermal annealing, 2D component of perovskite will increase while chloride decline, leading to improved photovoltage but reduced fill factor. Hence, it distinguishes that chloride enrichment can improve charge transport/ recombination simultaneously and 2D passivation can suppress the nonradiative recombination. Moreover, CHMAI can leverage their roles in charge transport/recombination for better performance than phenylethylammonium iodide (Cl/I = 0.114, PCE = 23.32%), due to the stronger binding energy of Cl − . This work provides the insight that the chloride fixation can improve the photovoltaic performance.

It is technically challenging to reversibly tune the layer number of 2D materials in the solution. Herein, a facile concentration modulation strategy is demonstrated to reversibly tailor the aggregation state of 2D ZnIn2S4 (ZIS) atomic layers, and they are implemented for effective photocatalytic hydrogen (H2) evolution. By adjusting the colloidal concentration of ZIS (ZIS‐X, X = 0.09, 0.25, or 3.0 mg mL−1), ZIS atomic layers exhibit the significant aggregation of (006) facet stacking in the solution, leading to the bandgap shift from 3.21 to 2.66 eV. The colloidal stacked layers are further assembled into hollow microsphere after freeze‐drying the solution into solid powders, which can be redispersed into colloidal solution with reversibility. The photocatalytic hydrogen evolution of ZIS‐X colloids is evaluated, and the slightly aggregated ZIS‐0.25 displays the enhanced photocatalytic H2 evolution rates (1.11 µmol m−2 h−1). The charge‐transfer/recombination dynamics are characterized by time‐resolved photoluminescence (TRPL) spectroscopy, and ZIS‐0.25 displays the longest lifetime (5.55 µs), consistent with the best photocatalytic performance. This work provides a facile, consecutive, and reversible strategy for regulating the photo‐electrochemical properties of 2D ZIS, which is beneficial for efficient solar energy conversion.